Network Address Translation (NAT) allows a single device such as a router to act as an agent between an internal private network and the public internet. NAT conserves IP addresses by mapping multiple unregistered private IP addresses to a single registered public IP address. There are different types of NAT including static NAT which maps private to public addresses on a one-to-one basis, dynamic NAT which maps to available public addresses, and port address translation (PAT) which overloads a public IP address by using different port numbers for each private address. NAT translates IP addresses for traffic entering and leaving the private network to allow communication while hiding the internal network topology.
This document discusses network address translation (NAT) and how it allows private IP addresses on a local network to connect to public IP addresses on the internet. It explains that NAT involves translating IP addresses and ports so that a private network can be represented by a single public IP address from the perspective of the internet. It also describes different types of NAT, such as basic NAT, port address translation, source NAT, and destination NAT. Specific scenarios like browsing the web, port forwarding, and issues with certain protocols like FTP are also covered at a high level.
Network Address Translation (NAT) allows a single device like a router to act as an agent between a private network and the public internet using a single public IP address. This conserves limited public IP addresses as only the NAT device needs a public IP, while an entire private network can use private IP addresses. NAT works by translating the private IP address and port of devices in the private network to the public IP address and unique port of the NAT device when communicating with the public internet, and vice versa for incoming traffic. This allows all private network devices to access the internet through the single public IP address of the NAT device.
Network Address Translation (NAT) allows devices on a private network to use public IP addresses to access the Internet. NAT translates private IP addresses to public IP addresses to conserve the limited number of public addresses. There are three main types of NAT: static NAT assigns a public IP to a device; dynamic NAT uses a pool of public IPs; and port address translation uses ports of a single public IP for multiple private devices. NAT provides advantages like acting as a firewall and allowing unlimited private devices to share a single public IP. However, it also causes some applications to work less effectively and complicates troubleshooting when IP addresses change.
This document discusses Network Address Translation (NAT) and how it allows private IP networks to connect to the Internet. It covers the problems of IP address exhaustion and depletion of IPv4 addresses. NAT enables private networks using unregistered IP addresses to connect to the public network by translating private IP addresses to public IP addresses. The document defines key NAT terms and describes how NAT is implemented on a router with inside and outside interfaces to translate packet headers. It also covers the types and advantages of NAT, including connecting multiple computers to the Internet using a single public IP address, as well as some disadvantages like added delay.
This document discusses network address translation (NAT) as a solution to problems with IP address depletion and routing scaling in the IP internet. It provides an introduction to NAT, describing it as a short-term solution that translates IP addresses to conserve addresses and allow routing to continue functioning. It then covers the different types of NAT implementations (static, dynamic, masquerading), how NAT works at a technical level using IP chains and IP tables, and considerations around when and why NAT may be used as well as limitations.
The document discusses DHCP, NAT, and forwarding of IP packets. It begins by explaining DHCP and how DHCP servers dynamically assign IP addresses and network configuration parameters to devices on a network. It then covers network address translation, how NAT allows private IP addresses to be mapped to public IP addresses. The document concludes by discussing how routers forward IP packets based on the destination address, and methods for routing tables and longest prefix matching to determine the appropriate path for packet forwarding.
Network Address Translation (NAT) allows multiple devices on a private network to share a single public IP address to connect to the internet. It works by translating the private IP addresses and port numbers in data packets into public IP addresses and port numbers before being sent out to the internet, and vice versa for incoming packets. Dynamic NAT assigns public IP addresses and port numbers from a pool to private addresses and ports on demand. Overloading allows multiple connections from the same private IP by using different port numbers. Proxies provide additional benefits like caching but require explicit client support. NAT can improve security, administration and fault tolerance but causes issues for some network games without workarounds.
NAT maps private IP addresses to public IP addresses, allowing multiple devices on a private network to share a single public IP address to access the Internet. It is commonly used when there is a shortage of IPv4 addresses. There are different types of NAT, including dynamic NAT which maps private addresses to public addresses on a need basis, and NAPT which allows thousands of devices to share one IP address by also mapping port numbers. NAT solves issues like merging networks with duplicate private addresses and changing ISPs without renumbering an entire network.
This document discusses network address translation (NAT) and how it allows private IP addresses on a local network to connect to public IP addresses on the internet. It explains that NAT involves translating IP addresses and ports so that a private network can be represented by a single public IP address from the perspective of the internet. It also describes different types of NAT, such as basic NAT, port address translation, source NAT, and destination NAT. Specific scenarios like browsing the web, port forwarding, and issues with certain protocols like FTP are also covered at a high level.
Network Address Translation (NAT) allows a single device like a router to act as an agent between a private network and the public internet using a single public IP address. This conserves limited public IP addresses as only the NAT device needs a public IP, while an entire private network can use private IP addresses. NAT works by translating the private IP address and port of devices in the private network to the public IP address and unique port of the NAT device when communicating with the public internet, and vice versa for incoming traffic. This allows all private network devices to access the internet through the single public IP address of the NAT device.
Network Address Translation (NAT) allows devices on a private network to use public IP addresses to access the Internet. NAT translates private IP addresses to public IP addresses to conserve the limited number of public addresses. There are three main types of NAT: static NAT assigns a public IP to a device; dynamic NAT uses a pool of public IPs; and port address translation uses ports of a single public IP for multiple private devices. NAT provides advantages like acting as a firewall and allowing unlimited private devices to share a single public IP. However, it also causes some applications to work less effectively and complicates troubleshooting when IP addresses change.
This document discusses Network Address Translation (NAT) and how it allows private IP networks to connect to the Internet. It covers the problems of IP address exhaustion and depletion of IPv4 addresses. NAT enables private networks using unregistered IP addresses to connect to the public network by translating private IP addresses to public IP addresses. The document defines key NAT terms and describes how NAT is implemented on a router with inside and outside interfaces to translate packet headers. It also covers the types and advantages of NAT, including connecting multiple computers to the Internet using a single public IP address, as well as some disadvantages like added delay.
This document discusses network address translation (NAT) as a solution to problems with IP address depletion and routing scaling in the IP internet. It provides an introduction to NAT, describing it as a short-term solution that translates IP addresses to conserve addresses and allow routing to continue functioning. It then covers the different types of NAT implementations (static, dynamic, masquerading), how NAT works at a technical level using IP chains and IP tables, and considerations around when and why NAT may be used as well as limitations.
The document discusses DHCP, NAT, and forwarding of IP packets. It begins by explaining DHCP and how DHCP servers dynamically assign IP addresses and network configuration parameters to devices on a network. It then covers network address translation, how NAT allows private IP addresses to be mapped to public IP addresses. The document concludes by discussing how routers forward IP packets based on the destination address, and methods for routing tables and longest prefix matching to determine the appropriate path for packet forwarding.
Network Address Translation (NAT) allows multiple devices on a private network to share a single public IP address to connect to the internet. It works by translating the private IP addresses and port numbers in data packets into public IP addresses and port numbers before being sent out to the internet, and vice versa for incoming packets. Dynamic NAT assigns public IP addresses and port numbers from a pool to private addresses and ports on demand. Overloading allows multiple connections from the same private IP by using different port numbers. Proxies provide additional benefits like caching but require explicit client support. NAT can improve security, administration and fault tolerance but causes issues for some network games without workarounds.
NAT maps private IP addresses to public IP addresses, allowing multiple devices on a private network to share a single public IP address to access the Internet. It is commonly used when there is a shortage of IPv4 addresses. There are different types of NAT, including dynamic NAT which maps private addresses to public addresses on a need basis, and NAPT which allows thousands of devices to share one IP address by also mapping port numbers. NAT solves issues like merging networks with duplicate private addresses and changing ISPs without renumbering an entire network.
Network Address Translation (NAT) allows private IP addresses on an inside network to be translated to public IP addresses when communicating with outside networks. Private IP addresses defined in RFC 1918 are illegal on the public internet. NAT is commonly used by home and small office routers to allow multiple private devices to share a single public IP address. Common NAT types include dynamic NAT, port address translation (PAT), and static NAT for servers. NAT extends the lifetime of IPv4 addresses but can cause issues for some applications.
A domain name provides a memorable way for users to access websites by typing a name instead of an IP address. The domain name directs the user to the IP address, which then directs them to the location of website files. Data sent over the internet is broken into smaller data packets that are reassembled at their destination. Routers determine the fastest route to send each data packet through the network and redirect packets if part of the network becomes busy or a server goes down.
Network Address Translation (NAT) allows private IP networks to connect to the public Internet using a single public IP address. NAT is run on routers and works by replacing the private IP addresses and port numbers in data packets with public IP addresses and port numbers when the packets leave the private network, and translating them back when packets return. This conserves public IP addresses and allows private networks to use non-routable address ranges while still accessing the Internet. Common NAT configurations include one-to-one mapping of addresses, IP masquerading of multiple private addresses to a single public address, and load balancing multiple servers accessed through a single public IP.
The IPv6 packet format consists of a 40-byte base header followed by optional extension headers and data from an upper layer. The base header contains fields for version, traffic class, flow label, payload length, next header, hop limit, source address, and destination address. Extension headers and upper layer data can total up to 65,535 bytes. Flow label is a new field that allows routers to identify and prioritize packets belonging to the same flow.
Network address translation (NAT) is a method of remapping one IP address space into another by modifying network address information in Internet Protocol (IP) datagram packet headers while they are in transit across a traffic routing device.
Network Address Translation (NAT) was developed as a solution to the limited number of available IP version 4 addresses. NAT allows multiple devices on a private network to share a single public IP address to access the internet. When data packets are sent from a device with a private IP address to the public internet, NAT translates the private address to a public address. Similarly, responses from the public internet have the public address translated back to the private address of the originating device. This process is transparent to users and allows more efficient use of available IP addresses. The future implementation of IP version 6 with its vastly larger address space is expected to eliminate the need for NAT.
The document describes the headers for IPv4 and IPv6 packets. IPv6 packet headers are simpler than IPv4 headers, with fewer fields but larger source and destination addresses. IPv6 also introduces extension headers to replace IPv4 options and allow additional optional information to be included. The transition from IPv4 to IPv6 will involve dual-stack implementations and tunneling IPv6 packets in IPv4 networks using special address types.
IPv6 was developed to replace IPv4 due to IPv4's limited address space and other issues. IPv6 uses 128-bit addresses compared to IPv4's 32-bit addresses, providing vastly more unique addresses. It also includes improvements in areas like security, quality of service, and extension headers. The transition from IPv4 to IPv6 is still ongoing, with strategies like running both protocols simultaneously, tunneling IPv6 traffic over IPv4, and translating headers to allow ongoing communication as adoption increases.
Network Address Translation (NAT) allows private IP addresses to be used within a local area network (LAN) while providing access to the public internet. NAT maps private IP addresses to public IP addresses, allowing multiple devices to share public IP addresses. The main NAT traversal challenges are that NAT prevents outside systems from initiating connections to inside systems and communication between systems that are both behind NAT routers. Proposed solutions include using third-party servers to reverse connections or techniques like UDP and TCP hole punching that establish connections directly between systems.
IPv6 was developed to address limitations in IPv4, such as the depletion of available IPv4 addresses. IPv6 features a 128-bit address space providing vastly more addresses than IPv4. It uses a simplified header structure compared to IPv4, removing unnecessary fields and expanding others. IPv6 also supports stateless autoconfiguration allowing nodes to automatically assign themselves addresses. Extension headers provide additional optional information for areas like routing, fragmentation, security and more. IPv6 aims to resolve issues with IPv4 and build upon lessons learned from over 20 years of IPv4 usage on the internet.
NAT is used to translate private IP addresses to public IP addresses to allow access to the internet. There are different types of NAT including static NAT for one-to-one mapping, dynamic NAT for mapping multiple private addresses to public addresses from a pool, and NAT overload/PAT which maps multiple private addresses to a single public address using port addressing. The document provides configuration examples for static, dynamic, and overload NAT on a Cisco router.
IPv4 uses 32-bit addresses represented in decimals, while IPv6 uses 128-bit addresses represented in hexadecials. IPv6 has built-in IPSec support, packet flow identification, and address auto-configuration, whereas IPv4 has optional IPSec, no packet identification, and requires manual or dynamic configuration. Other differences include IPv6 eliminating broadcast messages, checksum fields, and options fields, while IPv4 supports fragmentation by routers and uses ARP and IGMP which are replaced by NDP and MLD in IPv6.
IPv6 addresses are 128-bit identifiers for interfaces compared to 32-bit in IPv4. The presentation discusses the various address formats and types in IPv6 including unicast, anycast, and multicast. It also covers the changes in IPv6 packet header format versus IPv4 as well as new features like flow labeling and extension headers. Key advantages of IPv6 are larger address space, simplified header format, improved support for extensions, and better mobility and security features.
The document discusses several internet protocols including Internet Protocol (IP), File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), Secure Sockets Layer (SSL), Telnet, and Gopher. IP is the basic protocol that defines how data is sent between computers on the internet. FTP allows file transfers between systems, HTTP is used for web pages, and HTTPS provides encryption through SSL for secure communication. Telnet allows remote login to systems, and Gopher provides menu-based browsing of internet resources.
This document provides an introduction and overview of IPv6, including:
- IPv6 is the next generation internet protocol that will replace IPv4, providing a vastly larger address space and additional features.
- The key reasons for adopting IPv6 are that IPv4 addresses are running out due to the exponential growth of internet-connected devices, while IPv6 supports 128-bit addresses providing trillions of times more addresses.
- IPv6 addresses are 128-bit compared to 32-bit IPv4 addresses, written in hexadecimal format divided into eight groups, and features include improved security, mobility, and traffic routing capabilities.
Mobile IP is an IETF standard that allows mobile devices to change location between networks while maintaining the same IP address. It works by having a home agent forward data to the mobile node's current foreign agent when it is away from its home network. All data uses the mobile node's home address, while the care-of address identifies its current location and is used for tunneling data through foreign agents back to the mobile node.
The document discusses IPv4 routing and routing protocols. It begins with an introduction to routing and how data flows between devices on the internet in the form of packets. It then covers routing components like path determination, routing tables, and routing protocols for both intra-domain (RIP, OSPF) and inter-domain (BGP) routing. It concludes with a discussion on the future of routing with IPv6 and a high-level summary of routing and routing protocols.
This document provides an overview of hole punching techniques for establishing direct peer-to-peer connections between devices located behind firewalls or network address translation (NAT). It describes ICMP, TCP, and UDP hole punching protocols. Hole punching allows two devices to connect by establishing outbound connections through a third-party server that exchanges the devices' private address and port information. This allows the devices to try connecting to each other directly. The document also discusses NAT and its advantages and disadvantages.
The document provides information about network address translation (NAT) for IPv4. It discusses the purpose and functions of NAT, different types of NAT including static NAT, dynamic NAT, and port address translation (PAT). The advantages of NAT include conserving IPv4 addresses and hiding internal network addresses. Disadvantages include increased delays and loss of end-to-end addressing and traceability. The document also provides configuration instructions for different NAT types on Cisco routers.
IP addresses are unique identifiers for devices connected to a network. They allow information to be specifically routed to the intended destination similar to mailing addresses. There are two main IP address standards, IPv4 and IPv6, with IPv6 addressing anticipated space limitations of IPv4 by expanding the number of available addresses. IP addresses can be static, configured manually, or dynamic, assigned automatically by a DHCP server.
Network Address Translation (NAT) allows private IP addresses on an inside network to be translated to public IP addresses when communicating with outside networks. Private IP addresses defined in RFC 1918 are illegal on the public internet. NAT is commonly used by home and small office routers to allow multiple private devices to share a single public IP address. Common NAT types include dynamic NAT, port address translation (PAT), and static NAT for servers. NAT extends the lifetime of IPv4 addresses but can cause issues for some applications.
A domain name provides a memorable way for users to access websites by typing a name instead of an IP address. The domain name directs the user to the IP address, which then directs them to the location of website files. Data sent over the internet is broken into smaller data packets that are reassembled at their destination. Routers determine the fastest route to send each data packet through the network and redirect packets if part of the network becomes busy or a server goes down.
Network Address Translation (NAT) allows private IP networks to connect to the public Internet using a single public IP address. NAT is run on routers and works by replacing the private IP addresses and port numbers in data packets with public IP addresses and port numbers when the packets leave the private network, and translating them back when packets return. This conserves public IP addresses and allows private networks to use non-routable address ranges while still accessing the Internet. Common NAT configurations include one-to-one mapping of addresses, IP masquerading of multiple private addresses to a single public address, and load balancing multiple servers accessed through a single public IP.
The IPv6 packet format consists of a 40-byte base header followed by optional extension headers and data from an upper layer. The base header contains fields for version, traffic class, flow label, payload length, next header, hop limit, source address, and destination address. Extension headers and upper layer data can total up to 65,535 bytes. Flow label is a new field that allows routers to identify and prioritize packets belonging to the same flow.
Network address translation (NAT) is a method of remapping one IP address space into another by modifying network address information in Internet Protocol (IP) datagram packet headers while they are in transit across a traffic routing device.
Network Address Translation (NAT) was developed as a solution to the limited number of available IP version 4 addresses. NAT allows multiple devices on a private network to share a single public IP address to access the internet. When data packets are sent from a device with a private IP address to the public internet, NAT translates the private address to a public address. Similarly, responses from the public internet have the public address translated back to the private address of the originating device. This process is transparent to users and allows more efficient use of available IP addresses. The future implementation of IP version 6 with its vastly larger address space is expected to eliminate the need for NAT.
The document describes the headers for IPv4 and IPv6 packets. IPv6 packet headers are simpler than IPv4 headers, with fewer fields but larger source and destination addresses. IPv6 also introduces extension headers to replace IPv4 options and allow additional optional information to be included. The transition from IPv4 to IPv6 will involve dual-stack implementations and tunneling IPv6 packets in IPv4 networks using special address types.
IPv6 was developed to replace IPv4 due to IPv4's limited address space and other issues. IPv6 uses 128-bit addresses compared to IPv4's 32-bit addresses, providing vastly more unique addresses. It also includes improvements in areas like security, quality of service, and extension headers. The transition from IPv4 to IPv6 is still ongoing, with strategies like running both protocols simultaneously, tunneling IPv6 traffic over IPv4, and translating headers to allow ongoing communication as adoption increases.
Network Address Translation (NAT) allows private IP addresses to be used within a local area network (LAN) while providing access to the public internet. NAT maps private IP addresses to public IP addresses, allowing multiple devices to share public IP addresses. The main NAT traversal challenges are that NAT prevents outside systems from initiating connections to inside systems and communication between systems that are both behind NAT routers. Proposed solutions include using third-party servers to reverse connections or techniques like UDP and TCP hole punching that establish connections directly between systems.
IPv6 was developed to address limitations in IPv4, such as the depletion of available IPv4 addresses. IPv6 features a 128-bit address space providing vastly more addresses than IPv4. It uses a simplified header structure compared to IPv4, removing unnecessary fields and expanding others. IPv6 also supports stateless autoconfiguration allowing nodes to automatically assign themselves addresses. Extension headers provide additional optional information for areas like routing, fragmentation, security and more. IPv6 aims to resolve issues with IPv4 and build upon lessons learned from over 20 years of IPv4 usage on the internet.
NAT is used to translate private IP addresses to public IP addresses to allow access to the internet. There are different types of NAT including static NAT for one-to-one mapping, dynamic NAT for mapping multiple private addresses to public addresses from a pool, and NAT overload/PAT which maps multiple private addresses to a single public address using port addressing. The document provides configuration examples for static, dynamic, and overload NAT on a Cisco router.
IPv4 uses 32-bit addresses represented in decimals, while IPv6 uses 128-bit addresses represented in hexadecials. IPv6 has built-in IPSec support, packet flow identification, and address auto-configuration, whereas IPv4 has optional IPSec, no packet identification, and requires manual or dynamic configuration. Other differences include IPv6 eliminating broadcast messages, checksum fields, and options fields, while IPv4 supports fragmentation by routers and uses ARP and IGMP which are replaced by NDP and MLD in IPv6.
IPv6 addresses are 128-bit identifiers for interfaces compared to 32-bit in IPv4. The presentation discusses the various address formats and types in IPv6 including unicast, anycast, and multicast. It also covers the changes in IPv6 packet header format versus IPv4 as well as new features like flow labeling and extension headers. Key advantages of IPv6 are larger address space, simplified header format, improved support for extensions, and better mobility and security features.
The document discusses several internet protocols including Internet Protocol (IP), File Transfer Protocol (FTP), Hypertext Transfer Protocol (HTTP), Secure Sockets Layer (SSL), Telnet, and Gopher. IP is the basic protocol that defines how data is sent between computers on the internet. FTP allows file transfers between systems, HTTP is used for web pages, and HTTPS provides encryption through SSL for secure communication. Telnet allows remote login to systems, and Gopher provides menu-based browsing of internet resources.
This document provides an introduction and overview of IPv6, including:
- IPv6 is the next generation internet protocol that will replace IPv4, providing a vastly larger address space and additional features.
- The key reasons for adopting IPv6 are that IPv4 addresses are running out due to the exponential growth of internet-connected devices, while IPv6 supports 128-bit addresses providing trillions of times more addresses.
- IPv6 addresses are 128-bit compared to 32-bit IPv4 addresses, written in hexadecimal format divided into eight groups, and features include improved security, mobility, and traffic routing capabilities.
Mobile IP is an IETF standard that allows mobile devices to change location between networks while maintaining the same IP address. It works by having a home agent forward data to the mobile node's current foreign agent when it is away from its home network. All data uses the mobile node's home address, while the care-of address identifies its current location and is used for tunneling data through foreign agents back to the mobile node.
The document discusses IPv4 routing and routing protocols. It begins with an introduction to routing and how data flows between devices on the internet in the form of packets. It then covers routing components like path determination, routing tables, and routing protocols for both intra-domain (RIP, OSPF) and inter-domain (BGP) routing. It concludes with a discussion on the future of routing with IPv6 and a high-level summary of routing and routing protocols.
This document provides an overview of hole punching techniques for establishing direct peer-to-peer connections between devices located behind firewalls or network address translation (NAT). It describes ICMP, TCP, and UDP hole punching protocols. Hole punching allows two devices to connect by establishing outbound connections through a third-party server that exchanges the devices' private address and port information. This allows the devices to try connecting to each other directly. The document also discusses NAT and its advantages and disadvantages.
The document provides information about network address translation (NAT) for IPv4. It discusses the purpose and functions of NAT, different types of NAT including static NAT, dynamic NAT, and port address translation (PAT). The advantages of NAT include conserving IPv4 addresses and hiding internal network addresses. Disadvantages include increased delays and loss of end-to-end addressing and traceability. The document also provides configuration instructions for different NAT types on Cisco routers.
IP addresses are unique identifiers for devices connected to a network. They allow information to be specifically routed to the intended destination similar to mailing addresses. There are two main IP address standards, IPv4 and IPv6, with IPv6 addressing anticipated space limitations of IPv4 by expanding the number of available addresses. IP addresses can be static, configured manually, or dynamic, assigned automatically by a DHCP server.
Describe how a NAT (Network Address Translator) works. Be sure to in.pdfarishmarketing21
Describe how a NAT (Network Address Translator) works. Be sure to include an example
showing the translation.
Solution
Hi there well here is how the NAT works.
Network Address Translation (NAT) is mainly designed for conserving IP addresses.
It enables private IP networks that use unregistered IP addresses to connect to the Internet.
NAT operates on a router, which involves connection of two networks together, and
translates the private addresses in the internal network into legal addresses,
before the data packets are being forwarded to another network.
NAT allows a single device, such as a router, to act as an agent between the Internet (or public
network) and a local network (or private network),
which means that only a single unique IP address is required to represent an entire group of
computers to anything outside their network.
NAT also maintains concurrent sessions.
Working of a NAT:
Earlier the computers and servers which are interacting with each other within a network need a
unique identification like
they should have a unique address to recognize each other.For this combinations of 32bit
numbers like IPv4 came into existence.But due to the faster growth
and demand of internet this was not suffiecient enough so to resolve this problem NAT came
into light.
It enabled two types of network IP addresses like private and public.
A range of private addresses were introduced, which anyone could use, as long as these were
kept private within the network and not routed on the internet.
The range of private addresses known as RFC 1918 are;
Class A 10.0.0.0 - 10.255.255.255
Class B 172.16.0.0 - 172.31.255.255
Class C 192.168.0.0 - 192.168.255.255
NAT allows you to use these private IP address on the internal network.
However when internal hosts do need to communicate to the public network (Internet) then this
is where a public address comes into the equation.
Example of NAT:
For this we have to follow some policies:
Determine which IP addresses will be used for translation.
Set up the necessary proxy ARPs.
Set up the necessary static host routes.
Create the necessary network objects.
Make the necessary modifications to anti-spoofing.
Create the necessary rulebase rules to permit the desired traffic.
Create the NAT rules.
Install the security policy, and verify that everything works as planned..
This document provides an overview of internetworking and routing concepts. It defines internetworking as connecting two or more computer networks using devices like routers and a common addressing scheme. The three main types of internetworks are extranets, intranets, and the public Internet. IP is the common protocol used for internetworking and routing. IP packets contain source and destination addresses and are forwarded through routers using routing protocols. Performance factors like delay, throughput and packet loss are also discussed.
NAT enables private IP networks to connect to the public Internet by allowing private IP addresses to be translated to public IP addresses. There are three main types of NAT: static NAT maps individual private IPs to public IPs manually; dynamic NAT maps private IPs to public IPs automatically from address pools; and PAT maps multiple private IPs and ports to a single public IP and port numbers to distinguish connections. NAT allows private addressing in local networks while also connecting to the public Internet using public IP addresses.
How to configure static nat on cisco routersIT Tech
This document provides instructions for configuring static network address translation (NAT) on a Cisco router to map a private IP address to a public IP address. It explains that NAT allows private IP addresses on an internal network to be represented by public IP addresses on the external network. It then outlines the steps to configure static NAT on a Cisco router by defining the inside and outside interfaces, and using commands like "ip nat inside" and "ip nat outside" to identify the interfaces and "ip nat inside source static" to define the address mapping. It verifies the NAT configuration is working properly using show commands.
The document discusses networking concepts such as the difference between the internet and a network, internetworking, internet protocols, internet architecture, TCP/IP models, address mapping protocols, dynamic host configuration protocol, and domain name system servers. It provides definitions and explanations of these topics, describing for example that the internet is a global network of interconnected computer networks that uses common protocols like TCP/IP to connect devices, while a network is a set of devices connected locally.
IPv4 and IPv6 are internet protocols. IPv4 is the current version but IPv6 is needed to replace it due to IPv4 running out of available addresses. IPv6 uses 128-bit addresses compared to IPv4's 32-bit addresses, vastly increasing the number of available addresses. IPv6 also includes improvements in areas like security, quality of service, and mobility support. The transition from IPv4 to IPv6 is ongoing but not yet complete, as both protocols need to coexist during the changeover period.
NAT (network address translation) & PAT (port address translation)Netwax Lab
NAT (Network Address Translation) allows private IP networks to connect to the Internet by translating private IP addresses to public IP addresses. It operates on a router, connecting internal and external networks. NAT provides security by hiding internal network addresses and conserving IP addresses. There are various NAT types, including static NAT for one-to-one address mapping, dynamic NAT for mapping private addresses to public addresses from a pool, and NAT overload/PAT for mapping multiple private addresses to a single public address using ports.
NAT maps private IP addresses to public IP addresses, allowing multiple devices on a private network to share a single public IP address to access the Internet. It is commonly used to conserve public IP addresses and avoid renumbering networks when changing ISPs. There are different types of NAT including static NAT, dynamic NAT, and NAPT, each with different mapping behaviors between private and public addresses.
This document provides an overview of basic network and security concepts. It discusses TCP/IP, routing, DNS, NAT, firewalls, tunneling, and DMZs. It also covers web and security concepts such as proxies, reverse proxies, HTTP/HTTPS, and certificates. The document defines these terms and concepts at a high level to provide foundational understanding of computer networks and security.
Network address translation (NAT) allows remapping of one IP address space to another. Types of NAT include static NAT, dynamic NAT, and port address translation (PAT). NAT provides benefits like IP address conservation, security, and flexibility. On Cisco routers, NAT operations follow an order of inside-to-outside and outside-to-inside translation. NAT can be deployed in scenarios involving MPLS VPNs, IP multicast, high availability, and application-level gateways. Configuration of NAT varies between Cisco routers and ASA firewalls.
The document provides an introduction to computer networks and covers several key topics:
- It describes common networking protocols like TCP/IP and compares IPv4 and IPv6 addressing schemes.
- It explains IP addressing formats including classes A, B, C, D and E and how routing is used to transmit packets across networks.
- Interior and exterior routing protocols are defined, including examples like RIP, OSPF, BGP, and IS-IS.
- The roles of the Domain Name System (DNS) in mapping names to network resources and its hierarchical namespace are outlined.
As robust as the IP protocol is, it does not perform the actual .docxcargillfilberto
As robust as the IP protocol is, it does not perform the actual transmission of the data. In this step, you will investigate the network protocol called
Transmission Control Protocol (TCP)
, responsible for creation, reliability of delivery, and proper assembling of data packets.
In addition to IP, TCP is also widely used on the internet, especially for any network communication where it is essential to confirm receipt of the transmission. Many of the network protocols used to implement cloud computing use both TCP and IP. You will review TCP’s workings and discuss them in your final technical report.
In general, there is no guarantee that a data packet will reach its destination. Packets can get lost or corrupted during transmission, and there are network applications where you need assurance that the packets have reached their destination. To achieve reliability, TCP establishes connections between communicating hosts, using port numbers to refer to applications on these hosts. Then, packets are created, sequenced, transmitted, acknowledged, and retransmitted if missing or containing errors. Finally, at the destination, they are reassembled into the original messages.
To synchronize the flow of packets between sender and receiver, and avoid packet congestion in case of varying speeds, TCP uses
sliding windows
for packets remaining in processing at a given time, at both the sender and receiver ends.
In the next step, you will look into subnetting BallotOnline’s IP addresses.
One of the drawbacks of IPv4 is the maximum number of network devices it can support. IPv4 addressing uses a 32-bit network address. This allows for 232,, or a little over 4 billion devices. However, today there are significantly more devices on the internet. Even though the more robust IPv6 version has been introduced and efforts are under way to assure wide adoption, IPv4 is still widely used.
One method used to more efficiently use the IPv4 network addresses is a technique to optimize the addresses by splitting them into network addresses and host addresses within designated networks. You will need to take advantage of IP address splitting so that you can efficiently use and allocate the IPv4 network addresses that have been assigned to BallotOnline.
For a given large network, rather than addressing all the hosts using the host part of the address,
subnetting
allows for splitting the network into several smaller ones by borrowing the host part bits and adding them to the network bits. It supports efficient management of local networks composed of multiple LANs. In this step, you will investigate subnetting conventions and discuss them in your final report in order to lay ground for the use of subnets by BallotOnline.
As the network engineer for BallotOnline, you know that subnetting a network into several smaller and variable-sized networks will be best for the organization's needs. BallotOnline has been assigned a network address block by the
In.
An IP address is a unique string of numbers that identifies devices on the internet or a local network. There are two main types of IP addresses: IPv4 addresses, which have been in use for over 35 years, and IPv6 addresses, which are gradually replacing IPv4 due to IPv4 address exhaustion. IP addresses can be public, providing outside access to a network, or private for internal network use. Subnet masks allow IP addresses to be divided into a network and host portion to better organize large networks.
This document discusses Network Address Translation (NAT) and Port Address Translation (PAT). It defines key NAT terms and private IP address ranges. It then describes the main features of NAT and PAT, including static and dynamic NAT mappings and how PAT uses port numbers to map multiple private IPs to a single public IP. The document provides examples for configuring static NAT, dynamic NAT, and PAT. It also discusses troubleshooting NAT and changing dynamic NAT configurations.
Computer networks are a fundamental aspect of modern technology, enabling computers to communicate and share information with one another. This presentation will provide an overview of computer networks, covering topics such as network architecture, network topologies, network protocols, and network security. Participants will learn about different types of networks, such as LANs (Local Area Networks), WANs (Wide Area Networks), and the Internet. We will also discuss the different components of a network, including routers, switches, and servers, as well as the protocols used to transmit data across networks. Additionally, the presentation will cover topics related to network security, including firewalls, intrusion detection and prevention, and encryption. By the end of the presentation, participants will have a solid understanding of computer networks and the role they play in modern computing.
IP addresses are unique identifiers for devices connected to a network. There are four main types of IP addresses: public, private, static, and dynamic. Public IP addresses identify a device outside a network and are assigned by an ISP, while private IP addresses identify devices within a local network. Static IP addresses remain the same, whereas dynamic IP addresses can change over time. When data is sent between devices on different networks, routers use IP addresses to direct internet traffic to the proper destination.
This slide deck covers Networking Fundamentals, Various Penetration testing standards, OWASP TOP 10 Vulnerabilities of Web Application and the Lab Setup required for Penetration testing.
This document describes a CCN CEP project involving 3 group members to simulate a LAN network. The project involves configuring IP addresses, routers, servers, and VLANs. Connectivity is tested using ping commands between devices like PCs, servers, and across VLANs which are successful. Basic network functions like email and web access are also verified to work as intended. The simulation validates the network design and configuration.
Particle Swarm Optimization–Long Short-Term Memory based Channel Estimation w...IJCNCJournal
Paper Title
Particle Swarm Optimization–Long Short-Term Memory based Channel Estimation with Hybrid Beam Forming Power Transfer in WSN-IoT Applications
Authors
Reginald Jude Sixtus J and Tamilarasi Muthu, Puducherry Technological University, India
Abstract
Non-Orthogonal Multiple Access (NOMA) helps to overcome various difficulties in future technology wireless communications. NOMA, when utilized with millimeter wave multiple-input multiple-output (MIMO) systems, channel estimation becomes extremely difficult. For reaping the benefits of the NOMA and mm-Wave combination, effective channel estimation is required. In this paper, we propose an enhanced particle swarm optimization based long short-term memory estimator network (PSOLSTMEstNet), which is a neural network model that can be employed to forecast the bandwidth required in the mm-Wave MIMO network. The prime advantage of the LSTM is that it has the capability of dynamically adapting to the functioning pattern of fluctuating channel state. The LSTM stage with adaptive coding and modulation enhances the BER.PSO algorithm is employed to optimize input weights of LSTM network. The modified algorithm splits the power by channel condition of every single user. Participants will be first sorted into distinct groups depending upon respective channel conditions, using a hybrid beamforming approach. The network characteristics are fine-estimated using PSO-LSTMEstNet after a rough approximation of channels parameters derived from the received data.
Keywords
Signal to Noise Ratio (SNR), Bit Error Rate (BER), mm-Wave, MIMO, NOMA, deep learning, optimization.
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Here's where you can reach us : ijcnc@airccse.org or ijcnc@aircconline.com
Online train ticket booking system project.pdfKamal Acharya
Rail transport is one of the important modes of transport in India. Now a days we
see that there are railways that are present for the long as well as short distance
travelling which makes the life of the people easier. When compared to other
means of transport, a railway is the cheapest means of transport. The maintenance
of the railway database also plays a major role in the smooth running of this
system. The Online Train Ticket Management System will help in reserving the
tickets of the railways to travel from a particular source to the destination.
Data Communication and Computer Networks Management System Project Report.pdfKamal Acharya
Networking is a telecommunications network that allows computers to exchange data. In
computer networks, networked computing devices pass data to each other along data
connections. Data is transferred in the form of packets. The connections between nodes are
established using either cable media or wireless media.
Covid Management System Project Report.pdfKamal Acharya
CoVID-19 sprang up in Wuhan China in November 2019 and was declared a pandemic by the in January 2020 World Health Organization (WHO). Like the Spanish flu of 1918 that claimed millions of lives, the COVID-19 has caused the demise of thousands with China, Italy, Spain, USA and India having the highest statistics on infection and mortality rates. Regardless of existing sophisticated technologies and medical science, the spread has continued to surge high. With this COVID-19 Management System, organizations can respond virtually to the COVID-19 pandemic and protect, educate and care for citizens in the community in a quick and effective manner. This comprehensive solution not only helps in containing the virus but also proactively empowers both citizens and care providers to minimize the spread of the virus through targeted strategies and education.
Better Builder Magazine brings together premium product manufactures and leading builders to create better differentiated homes and buildings that use less energy, save water and reduce our impact on the environment. The magazine is published four times a year.
Sri Guru Hargobind Ji - Bandi Chor Guru.pdfBalvir Singh
Sri Guru Hargobind Ji (19 June 1595 - 3 March 1644) is revered as the Sixth Nanak.
• On 25 May 1606 Guru Arjan nominated his son Sri Hargobind Ji as his successor. Shortly
afterwards, Guru Arjan was arrested, tortured and killed by order of the Mogul Emperor
Jahangir.
• Guru Hargobind's succession ceremony took place on 24 June 1606. He was barely
eleven years old when he became 6th Guru.
• As ordered by Guru Arjan Dev Ji, he put on two swords, one indicated his spiritual
authority (PIRI) and the other, his temporal authority (MIRI). He thus for the first time
initiated military tradition in the Sikh faith to resist religious persecution, protect
people’s freedom and independence to practice religion by choice. He transformed
Sikhs to be Saints and Soldier.
• He had a long tenure as Guru, lasting 37 years, 9 months and 3 days
1. How NAT Works
Document ID: 6450
This document contains Flash animation
Contents
Introduction
Prerequisites
Requirements
Components Used
Conventions
Behind the Mask
Dynamic NAT and Overloading Examples
Flash Animation: Dynamic NAT
Security and Administration
Multi−Homing
Related Information
Introduction
If you are reading this, you are most likely connected to the Internet and there's a very good chance that you
are using Network Address Translation (NAT) right now!
The Internet has grown larger than anyone ever imagined it could be. Although the exact size is unknown, the
current estimate is that there are about 100 million hosts and over 350 million users actively on the Internet.
That is more than the entire population of the United States! In fact, the rate of growth has been such that the
Internet is effectively doubling in size each year.
So what does the size of the Internet have to do with NAT? Everything! For a computer to communicate with
other computers and Web servers on the Internet, it must have an IP address. An IP address (IP stands for
Internet Protocol) is a unique 32−bit number that identifies the location of your computer on a network.
Basically it works just like your street address: a way to find out exactly where you are and deliver
information to you.
When IP addressing first came out, everyone thought that there were plenty of addresses to cover any need.
Theoretically, you could have 4,294,967,296 unique addresses (232
). The actual number of available addresses
is smaller (somewhere between 3.2 and 3.3 billion) because of the way that the addresses are separated into
Classes and the need to set aside some of the addresses for multicasting, testing or other specific uses.
With the explosion of the Internet and the increase in home networks and business networks, the number of
available IP addresses is simply not enough. The obvious solution is to redesign the address format to allow
for more possible addresses. This is being developed (IPv6) but will take several years to implement because
it requires modification of the entire infrastructure of the Internet.
The NAT router translates traffic coming into and leaving the private network:
2. This is where NAT (RFC 1631 ) comes to the rescue. Basically, Network Address Translation allows a single
device, such as a router, to act as agent between the Internet (or "public network") and a local (or "private")
network. This means that only a single unique IP address is required to represent an entire group of computers
to anything outside their network.
The shortage of IP addresses is only one reason to use NAT. Two other good reasons are:
Security•
Administration•
You will learn more about how NAT can benefit you, but first, let us take a closer look at NAT and what it
can do&
Prerequisites
Requirements
Readers of this document should be knowledgeable of the following:
IP addressing and routing concepts•
Components Used
This document is not restricted to specific software and hardware versions.
Conventions
Refer to Cisco Technical Tips Conventions for more information on document conventions.
Behind the Mask
NAT is like the receptionist in a large office. Let's say you have left instructions with the receptionist not to
forward any calls to you unless you request it. Later on, you call a potential client and leave a message for
them to call you back. You tell the receptionist that you are expecting a call from this client and to put them
through.
The client calls the main number to your office, which is the only number the client knows. When the client
tells the receptionist who they are looking for, the receptionist checks a lookup table that matches up the
person's name and extension. The receptionist knows that you requested this call, therefore the receptionist
forwards the caller to your extension.
Developed by Cisco, Network Address Translation is used by a device (firewall, router or computer) that sits
between an internal network and the rest of the world. NAT has many forms and can work in several ways:
3. Static NAT Mapping an unregistered IP address to a registered IP address on a one−to−one basis.
Particularly useful when a device needs to be accessible from outside the network.
In static NAT, the computer with the IP address of 192.168.32.10 will always translate to
213.18.123.110:
•
Dynamic NAT Maps an unregistered IP address to a registered IP address from a group of
registered IP addresses. Dynamic NAT also establishes a one−to−one mapping between unregistered
and registered IP address, but the mapping could vary depending on the registered address available in
the pool, at the time of communication.
In dynamic NAT, the computer with the IP address of 192.168.32.10 will translate to the first
available address in the range from 213.18.123.100 to 213.18.123.150:
•
Overloading A form of dynamic NAT that maps multiple unregistered IP addresses to a single
registered IP address by using different ports. Known also as PAT (Port Address Translation), single
address NAT or port−level multiplexed NAT.
In overloading, each computer on the private network is translated to the same IP address
(213.18.123.100) but with a different port number assignment:
•
Overlapping When the IP addresses used on your internal network are registered IP addresses in
use on another network, the router must maintain a lookup table of these addresses so that it can
intercept them and replace them with registered unique IP addresses. It is important to note that the
NAT router must translate the "internal" addresses to registered unique addresses and also it must
translate the "external" registered addresses to addresses that are unique to the private network. This
can be done either through static NAT or you can use DNS and implement dynamic NAT.
The internal IP range (237.16.32.xx) is also a registered range used by another network.
Therefore, the router is translating the addresses to avoid a potential conflict with another
•
4. network. It will also translate the registered global IP addresses back to the unregistered local
IP addresses when information is sent to the internal network:
The internal network is usually a LAN (Local Area Network), commonly referred to as the stub domain. A
stub domain is a LAN that uses IP addresses internally. Most of the network traffic in a stub domain is local, it
doesn't travel off the internal network. A stub domain can include both registered and unregistered IP
addresses. Of course, any computers that use unregistered IP addresses must use Network Address Translation
to communicate with the rest of the world.
NAT can be configured in various ways. In the example below the NAT router is configured to translate
unregistered IP addresses (inside local addresses) that reside on the private (inside) network to registered IP
addresses. This happens whenever a device on the inside with an unregistered address needs to communicate
with the public (outside) network.
An ISP assigns a range of IP addresses to your company. The assigned block of addresses are
registered unique IP addresses and are called inside global addresses. Unregistered private IP
addresses are split into two groups, a small group (outside local addresses) that will be used by the
NAT routers and the majority that will be used on the stub domain known as inside local addresses.
The outside local addresses are used to translate the unique IP addresses, known as outside global
addresses, of devices on the public network. For more information on definitions of local and global
addresses, refer to NAT: Local and Global Definitions. NAT only translates traffic which travel
between the inside and outside network and is specified to be translated. Any traffic not matching the
translation criteria or those that are forwarded between other interfaces on a router are never
translated, and they are forwarded as such.
IP addresses have different designations based on whether they are on the private network (stub
domain) or on the public network (Internet) and whether the traffic is incoming or outgoing:
•
Most computers on the stub domain communicate with each other using the inside local addresses.•
Some computers on the stub domain communicate a lot outside the network. These computers have
inside global addresses which means that they do not require translation.
•
When a computer on the stub domain that has an inside local address wants to communicate outside
the network, the packet goes to one of the NAT routers by way of normal routing to the
default−gateway.
•
The NAT router checks the routing table to see if it has an entry for the destination address. If the
destination address is not in the routing table, the packet is dropped. If an entry is available, it verifies
whether the packet is traveling from the inside to the outside network and checks if the packet
matches the criteria specified for translation. The router then checks the address translation table to
•
5. find if there is an entry existing for the inside local address with a corresponding inside global
address. If an entry is found, it translates the packet by using the inside global address. If static NAT
alone is configured and no entry is found, it sends the packet without translation.
Using an inside global address, the router sends the packet on to its destination.•
A computer on the public network sends a packet to the private network. The source address on the
packet is an outside global address. The destination address is an inside global address.
•
When the packet arrives on the outside network, the NAT router looks at the address translation table
and determines that the destination address is in there, mapped to a computer on the stub domain.
•
The NAT router translates the inside global address of the packet to the inside local address and then
checks the routing table before it sends it to the destination computer. Whenever an entry is not found
for an address in the translation table, it is not translated and proceeds with verifying the routing table
for the destination address. The packet is dropped if a route to the destination is not found in the
routing table.
•
For more information on the order in which transactions are processed using NAT, refer to NAT Order of
Operation.
NAT overloading utilizes a feature of the TCP/IP protocol stack, multiplexing, that allows a computer to
maintain several concurrent connections with a remote computer(s) using different TCP or UDP ports. An IP
packet has a header that contains the following information:
Source AddressThe IP address of the originating computer, for example, 201.3.83.132.•
Source PortThe TCP or UDP port number assigned by the originating computer for this packet, for
example, Port 1080.
•
Destination AddressThe IP address of the receiving computer. For example, 145.51.18.223.•
Destination PortThe TCP or UDP port number the originating computer is requesting the receiving
computer to open, for example, Port 3021.
•
The addresses specify the two machines at each end while the port numbers ensure that the connection
between the two computers has a unique identifier. The combination of these four numbers defines a single
TCP/IP connection. Each port number uses 16 bits, which means that there are a possible 65,536 (216) values.
Realistically, since different manufacturers map the ports in slightly different ways, you can expect to have
about 4,000 ports available.
Dynamic NAT and Overloading Examples
Flash Animation: Dynamic NAT
Here is how dynamic NAT works:
Go to the Dynamic NAT Flash animation and click on one of the green buttons to send a successful
packet either to or from the stub domain. Click on one of the red buttons to send a packet that is dropped by
the router because of an invalid address.
An internal network (stub domain) has been set up with IP addresses that were not specifically
allocated to that company by IANA (Internet Assigned Numbers Authority), the global authority
that hands out IP addresses. These addresses should be considered non−routable since they are not
unique. These are the inside local addresses.
•
The company sets up a router with NAT enabled. The router has a range of unique IP addresses given
to the company by IANA. These are the inside global addresses.
•
A computer on the stub domain attempts to connect to a computer outside the network, such as a Web
server.
•
6. The router receives the packet from the computer on the stub domain.•
After checking the routing table and the verification process for translation to occur, the router saves
the computer's non−routable IP address to an address translation table. The router replaces the
sending computer's non−routable IP address with the first available IP address out of the range of
unique IP addresses. The translation table now has a mapping of the computer's non−routable IP
address matched with one of the unique IP addresses.
•
When a packet comes back from the destination computer, the router checks the destination address
on the packet. It then looks in the address translation table to see which computer on the stub domain
the packet belongs to. It changes the destination address to the one saved in the address translation
table and sends it to that computer. If it doesn't find a match in the table, it drops the packet.
•
The computer receives the packet from the router and the process repeats as long as the computer is
communicating with the external system.
•
Here's how overloading works:
An internal network (stub domain) has been set up with non−routable IP addresses that were not
specifically allocated to that company by IANA.
•
The company sets up a router with NAT enabled. The router has a unique IP address given to the
company by IANA.
•
A computer on the stub domain attempts to connect to a computer outside the network, such as a Web
server.
•
The router receives the packet from the computer on the stub domain.•
After routing and verifying the packet for translation, the router saves the computer's non−routable IP
address and port number to an address translation table. The router replaces the sending computer's
non−routable IP address with the router's IP address. The router replaces the sending computer's
source port with the port number that matches where the router saved the sending computer's address
information in the address translation table. The translation table now has a mapping of the
computer's non−routable IP address and port number along with the router's IP address.
•
When a packet comes back from the destination computer, the router checks the destination port on
the packet. It then looks in the address translation table to see which computer on the stub domain the
packet belongs to. It changes the destination address and destination port to the one saved in the
address translation table and sends it to that computer.
•
The computer receives the packet from the router and the process repeats as long as the computer is
communicating with the external system.
•
Since the NAT router now has the computer's source address and source port saved to the address
translation table, it will continue to use that same port number for the duration of the connection. A
timer is reset each time the router accesses an entry in the table. If the entry is not accessed again
before the timer expires, the entry is removed from the table.
•
Look at the following table to see how the computers on a stub domain might appear to any external
networks:
Source
Computer
Source
Computer's
IP Address
Source
Computer's
Port
NAT Router's
IP Address
NAT
Router's
Assigned
Port
Number
A
192.168.32.10 400 215.37.32.203 1
B
192.168.32.13 50 215.37.32.203 2
C
192.168.32.15 3750 215.37.32.203 3
D
192.168.32.18 206 215.37.32.203 4
7. As you can see, the NAT router stores the IP address and port number of each computer in the address
translation table. It then replaces the IP address with its own registered IP address and the port number
corresponding to the location of the entry for that packet's source computer in the table. So any external
network sees the NAT Router's IP address and the port number assigned by the router as the source computer
information on each packet.
You can still have some computers on the stub domain that use dedicated IP addresses. You can create an
access list of IP addresses that tells the router which computers on the network require NAT. All other IP
addresses will pass through untranslated.
The number of simultaneous translations that a router will support is determined mainly by the amount of
DRAM (Dynamic Random Access Memory) it has. But since a typical entry in the address translation table
only takes about 160 bytes, a router with 4 MB of DRAM could theoretically process 26,214 simultaneous
translations! Which is more than enough for most applications.
IANA has actually set aside specific ranges of IP addresses for use as non−routable internal network
addresses. These addresses are considered unregistered, ( for more information check out RFC 1918: Address
Allocation for Private Internets which defines these address ranges) which means that no company or agency
can claim ownership of them and use them on public computers. Routers do not forward packets to
unregistered addresses since those networks are meant for private use and are not supposed to be advertised to
outside world. What this means is that a packet from a computer with an unregistered address could reach a
registered destination computer, but the reply would be discarded by the first router it came to.
There is a range for each of the three classes of IP addresses used for networking.
Range 1 is for Class A: 10.0.0.0 through 10.255.255.255•
Range 2 is Class B: 172.16.0.0 through 172.31.255.255•
Range 3 is Class C: 192.168.0.0 through 192.168.255.255•
Although each range is in a different class, there is no requirement that you use any particular range for your
internal network. It is good practice though because it greatly diminishes the chance of an IP address conflict.
When you modify an existing Dynamic NAT configuration, you may be prompted with these error messages
while the NAT translation is active:
Dynamic mapping in use, cannot remove•
%Pool outpool in use, cannot destroy•
For these types of error messages, please refer to How to Change the Dynamic NAT Configuration which
describes the procedure to clear the active NAT translation and modify the configuration accordingly.
Security and Administration
Implementing dynamic NAT automatically creates a firewall between your internal network and outside
networks or the Internet. Dynamic NAT allows only connections that originate inside the stub domain.
Essentially, this means that a computer on an external network cannot connect to your computer unless your
computer has initiated the contact. So you can browse the Internet and connect to a site, even download a file.
But somebody else can't simply latch onto your IP address and use it to connect to a port on your computer.
Static NAT, also called inbound mapping, allows connections initiated by external devices to computers on
the stub domain to take place in specific circumstances. For instance, you may wish to map an inside global
address to a specific inside local address that is assigned to your Web server.
8. Static NAT (inbound mapping) allows a computer on the stub domain to maintain a specific address
when communicating with devices outside the network:
Some NAT routers provide for extensive filtering and traffic logging. Filtering allows your company to
control what type of sites employees visit on the Web, preventing them from viewing questionable material.
You can use traffic logging to create a log file of what sites are visited and generate various reports from it.
Network Address Translation is sometimes confused with proxy servers but there are definite differences.
NAT is transparent to the source and destination computers. Neither one realizes that it is dealing with a third
device. But a proxy server is not transparent. The source computer knows that it is making a request to the
proxy server and must be configured to do so. The destination computer thinks that the proxy server IS the
source computer and deals with it directly. Also, proxy servers usually work at Layer 4 (Transport) of the OSI
Reference Model or higher, while NAT is a Layer 3 (Network) protocol. Working at a higher layer makes
proxy servers slower than NAT devices in most cases.
NAT operates at the Network layer (Layer 3) of the OSI Reference Model which makes sense, because
this is the layer at which routers work:
A real benefit of NAT is apparent in network administration. For example, you can move your Web server or
FTP server to another host computer without having to worry about broken links. Simply change the inbound
9. mapping with the new inside local address at the router to reflect the new host. You can also make changes to
your internal network easily since the only external IP address either belongs to the router or comes from a
pool of global addresses.
NAT and DHCP are a natural fit, you can choose a range of unregistered IP addresses for your stub domain
and have the DHCP server dole them out as necessary. It also makes it much easier to scale up your network
as your needs grow. You don't have to request more IP addresses from IANA. You can just increase the range
of available IP addresses configured in DHCP and immediately have room for additional computers on your
network.
Multi−Homing
As businesses rely more and more on the Internet, having multiple points of connection to the Internet is fast
becoming an integral part of their network strategy. Multiple connections, known as multi−homing, reduces
the chance of a potentially catastrophic shutdown if one of the connections should fail.
In addition to maintaining a reliable connection, multi−homing allows a company to perform load−balancing
by lowering the number of computers connecting to the Internet through any single connection. Distributing
the load through multiple connections optimizes the performance and can significantly decrease wait times.
Multi−homed networks are often connected to several different ISPs (Internet Service Providers). Each ISP
assigns an IP address (or range of IP addresses) to the company. Routers use BGP (Border Gateway
Protocol), a part of the TCP/IP protocol suite, to route between networks using different protocols. In a
multi−homed network, the router utilizes IBGP (Internal Border Gateway Protocol) on the stub domain
side and EBGP (External Border Gateway Protocol) to communicate with other routers. When using NAT
with multi−homing, the NAT router is configured with multiple pools of inside global addresses allocated by
different ISPs. The same inside local address should be mapped to more than one inside global address from
the configured pools, depending on the provider through which the traffic gets routed to the destination. This
is known as NAT by destination. Refer to NAT − Ability to Use Route Maps with Static Translations for
more information.
Multi−homing really makes a difference if one of the connections to an ISP fails. As soon as the router
assigned to connect to that ISP determines that the connection is down, it will reroute all data through one of
the other routers.
NAT can be used to facilitate scalable routing for mulit−homed multi−provider connectivity.
Related Information
Configuring Network Address Translation: Getting Started•
How to Change the Dynamic NAT Configuration•
Basic rule of NAT (incoming and outgoing) & how to use "Ip nat inside destination"•
Cisco IOS Network Address Translation•
Cisco IOS Network Address Translation Overview•
Configuring IP Addressing•
Using NAT in Overlapping Networks•
NAT Order of Operation•
The Internet Protocol Journal: The Trouble with NAT•
RFC 1631: The IP Network Address Translator (NAT)•
RFC 1918: Address Allocation for Private Internets•
KnowledgeShare − White Papers: Network Address Translation FAQ•
NAT Technical Discussion•
Technical Support & Documentation − Cisco Systems•