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Chapter 2
Layer-2 Switching
Exam Essentials
Remember the three switch functions. Address learning, forward/filter
decision, and loop avoidance are the functions of a switch.
Understand the main purpose of the spanning tree in a switched LAN.
The main purpose of STP is to prevent switching loops in a network with
redundant switched paths.
Remember the three LAN switch methods. The three LAN switch
methods are cut-through, FragmentFree (also known as modified cut-
through) and store-and-forward.
Understand how the cut-through LAN switch method works. When in
this mode, the switch waits only for the destination hardware address to
be received before it looks up the address in the MAC filter table.
Understand how the FragmentFree LAN switch method works. The
FragmentFree LAN switch method checks the first 64 bytes of a frame
before forwarding it for fragmentation.
Understand how the store-and-forward LAN switch method works.
Store-and-forward first receives the complete data frame on the switch's
buffer; a CRC is run, and then the switch looks up the destination address
in the MAC filter table.
Key Terms
B
efore taking the exam, be sure you're familiar with the following
terms:
address learning
frame filtering
Bridge Protocol Data Unit (BPDU) nondesignated port
broadcast storm
root bridge
cut-through
Spanning Tree Protocol (STP)
designated port
store-and-forward
FragmentFree
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