Layer 2 & layer 3 switching

MUHAMMAD MU’IZUDDIN BIN MUHSINON
SN097083
SECTION 02A
Assignment
- Difference between Layer 2 & Layer 3 Switching
Layer 2 Switching
- Function
 MAC addresses are learned from the incoming frames’ source addresses.
 A table of MAC addresses and their associated bridge and switch ports is built and
maintained.
 Broadcast and multicast frames are flooded out to all ports (except the one that
received the frame).
 Frames destined for unknown locations are flooded out to all ports (except the one
that received the frame).
 Bridges and switches communicate with each other using the Spanning Tree
Protocol to eliminate bridging loops.
 Performs essentially the same function as a transparent bridge.
 May have many ports and can perform hardware-based bridging.
 Frames are forwarded using specialized hardware, called application-specific
integrated circuits (ASIC).
One drawback to Layer 2 switching is that it cannot be scaled effectively. Switches must
forward broadcast frames to all ports, causing large switched networks to become large
broadcast domains.
In addition, Spanning Tree Protocol (STP) can have a slow convergence time when the
switch topology changes. STP also can block certain switch ports, preventing data transfer.
- Benefit
 Hardware-based bridging (MAC)
 Wire speed
 High speed
 Low latency

Layer 3 Switching
 Packets are forwarded at Layer 3, just as a router would do.
 Packets are switched using specialized hardware, ASIC, for high speed and low
latency.
 Packets can be forwarded with security control and quality of service (QoS) using
Layer 3 address information.
 Layer 3 switches are designed to examine and forward packets in high-speed LAN
environments. Whereas a router might impose a bottleneck to forwarding
throughput, a Layer 3 switch can be placed anywhere in the network, with little or
no performance penalty.
 Determine paths based on logical addressing
 Run layer 3 checksums (on header only)
 Use Time to Live (TTL)
 Process and respond to any option information
 Update Simple Network Management Protocol (SNMP) managers with Management
Information Base (MIB) information
 Provide Security
- Benefit
 Hardware-based packet forwarding
 High-performance packet switching
 High-speed scalability
 Low latency
 Lower per-port cost
 Flow accounting
 Quality of service (QoS)

Layer 2 & layer 3 switching

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