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Switch Port Fast0/1 interpretation

kcn
kcn asked
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Like to know the complete interpretation of below descriptions :-

Switch Port Fast0/1 .

Fast = Fast Ethernet Port
0 = ???
1 = Port number 1 of that Switch .

What is that "0"  for ??

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0 - is number of interface (selected with interface command), after slash - port number (if available)
For example it could be used for Cisco WIC-4ESW - four port switch module
Instructor
Top Expert 2015
Commented:
In the modular Cisco switches there are slots that "line cards" are inserted into. The slots are numbered 1 through however many slots the switch has. In some cases, up to 18.

The line cards have the actual ethernet (or fastethernet or gigabitethernet) interfaces on them.

The first number indicates which slot (or line card). The second number indicates the physical interface on that line card.

So fa4/15 would be the 15th interface on the line card in slot 4.

A while back Cisco made the decision to make the port naming consistent across all the switch platforms. So now the non-modular platforms (2950, 3550, etc.) also have a two part interface identifier. But on the  number that indicates the slot number, a zero is used.

So fa0/7 would simply be the 7th interface.