Netw 471 Week 2

Topics: Network switch, Ethernet, IP address Pages: 4 (596 words) Published: May 21, 2014
DeVry University
NETW-471 week 2 

Switching  WhitePaper

Layer 2 Switching 
Source MAC addresses are learned from incoming frames.
A table of MAC addresses and their associated ports are built and maintained. Unknown unicast, broadcast and multicast frames are flooded to all ports (except the incoming port) Bridges and switches communicate with each other using spanning tree protocol to eliminate bridging loops. Layer 2 Switching 

A layer 2 switch performs the same functionality as a transparent bridge, however a switch is like a multiport bridge that performs hardware-based-bridging. Frames are forwarded using specialized hardware, called application-specific integrated circuits (ASIC). This hardware gives switching great scalability, with wire-speed performance, low latency, and high port density. As long as Layer 2 switch frames between two Layer 1 interfaces of the same media type, such as two Ethernet connection or an Ethernet connection and a Fast Ethernet connection, the frames do not have to be modified. However, if two interfaces are different media, such as Ethernet and Token Ring or Ethernet and Fibre Distributed data Interface (FDDI), the Layer 2 switch must translate the frame contents before sending out the Layer 1 interface.  

Layer 2 Switching 
One draw back to Layer 2 switching is that it can not be scaled effectively. Switches must forward broadcast traffic to all ports, causing large switched networks to become a large broadcast domain. In addition, STP can have a slow convergence time when the switch topology changes. Layer 2 switching alone can not provide an effective, scalable network design.  Layer 2 Switches 

Functions:
Source MAC Address learning
Filtering/ forwarding
Loop avoidance
Frame Switching Modes
Store and forward
Cut through
Fast Forwarding
Fragment Free
 
 

Layer 3 Switching 
Packets are forwarded at Layer 3, just as a router would do. Packets are switched using specialized hardware, ASIC, for...
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