mac address table per vlan

Answered Question
Nov 11th, 2008

hi every body!

Is there one mac address table for each vlan on a switch?

thanks a lot and have a nice day!

I have this problem too.
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Correct Answer by Jon Marshall about 8 years 2 weeks ago

Sarah

Cisco switches support per-vlan mac-address tables. As posted by John you can show all the mac-addresses specific to a vlan and you can also clear all mac-addresses specific to a vlan.

Jon

Correct Answer by John Blakley about 8 years 2 weeks ago

You can do a show mac addre vlan and it will tell you what mac addresses are on that vlan.

--John

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Correct Answer
John Blakley Tue, 11/11/2008 - 14:44

You can do a show mac addre vlan and it will tell you what mac addresses are on that vlan.

--John

Correct Answer
Jon Marshall Tue, 11/11/2008 - 15:02

Sarah

Cisco switches support per-vlan mac-address tables. As posted by John you can show all the mac-addresses specific to a vlan and you can also clear all mac-addresses specific to a vlan.

Jon

sarahr202 Wed, 11/12/2008 - 10:01

thanks for your reply.

From my cisco press book, i get the impression there is one cam table which contains:

mac port vlan#

for example:

0000.1111.1111 port 11 vlan 1

0000.2222.2222 port 12 vlan 2

The point is all mac addresses are in one single cam table for every vlans.

when we use the command:

show mac address-table dynamic vlan 2

then the mac addresses belonging to vlan 2 in cam table will be shown.

Am i correct?

thanks a lot!

Jon Marshall Wed, 11/12/2008 - 10:05

Sarah

I think it may well be the other way round on some switches (if not all). You actually have a per-vlan mac-address table but when you run "sh mac-address-table" the switch just combines them all into one output.

I don't know for sure if all switches support per-vlan mac-address tables.

Jon

sarahr202 Wed, 11/12/2008 - 11:28

thanks a lot for your reply Jon!

so when switch receives a frame, it first look at the vlan id to determine the corresponding mac address table to decide how to fooward the frame. Am i correct?

I was under the impression before i posted my question that switch use the mac address table which contains the mac addresss , vlans port to forward the frame.

Based on your response, it seems logical for a switch to first find the mac address table for particular vlan then forward the frame though my cisco book does not hint about it at all.

John Blakley Wed, 11/12/2008 - 10:05

I misread the post. Jon's correct. It's:

vlan mac type port number

Sorry for my original response. :-)

--John

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