show mac-address-table

[dtsaousoglou]

Given the command show mac-address-table from the privilege exec mode in a cat 2950, the output shows some (i think 4) mac-address tha are system. Do u have any idea what are these mac?

[peterledwidge]

Do you have any active hosts connected to the switch?

i.e. you may have a management IP Address

config t

int vlan x

ip address x.x.x.x 255.255.255.x

no shut

you could also try do a

show mac-address-table address xxxx.xxxx.xxxx

which should indicate if it is attached to a specific

interface.

HTH

Peter

[alagrawa]

Hi Dimitris,

Thanks for writing in. I tried the command on my switch and got the following: Do you see a similar output and is this what you are referring to?

2950#sh mac-address-table

Mac Address Table

-------------------------------------------

Vlan Mac Address Type Ports

---- ----------- -------- -----

All 0009.7c70.f9c0 STATIC CPU

All 0100.0ccc.cccc STATIC CPU

All 0100.0ccc.cccd STATIC CPU

All 0100.0cdd.dddd STATIC CPU

0100.0ccc.cccc is used for CDP/VTP/DTP/PAgP/UDLD

0100.0ccc.cccd is used for PVST+

0100.0cdd.dddd seems to be related to multicast, however need to confirm on this.

0009.7c70.f9c0 is the mac address for my management vlan interface.

2950#sh int vlan 1

Vlan1 is administratively down, line protocol is down Hardware is CPU Interface, address is 0009.7c70.f9c0 (bia 0009.7c70.f9c0)

Hope this helps.

regards

-Alok

[lgijssel]

Each switch has it's own mac address on board. This is called the BIA (burnt-in adress) and is required for a number of things:

1: spanning tree

2: for management purposes

3: for network communication

Hope this answers your question.

Regards,

Leo