mac address-table interface fastEthernet

thunder8080
thunder8080 used Ask the Experts™
on
Hi All,

When I type sw1#show mac address-table interface fastEthernet 1/2 command, I get this output:

sw1#show mac address-table interface fastEthernet 1/2
Multicast Entries
 vlan    mac address     type    ports
-------+---------------+-------+--------------------------------------------
 345 ffff.ffff.ffff   system Fa2/1,Fa2/2,Fa2/3,Fa2/4,Fa2/5,Fa2/6,Fa2/9
                               Fa3/37,Fa3/39,Fa3/42,Fa3/44,Fa3/46,Fa3/48
                                Gi1/1
 765 ffff.ffff.ffff   system Fa2/1,Fa2/2,Fa2/3,Fa2/4,Fa2/5,Fa2/6,Fa2/9
                                Fa2/10,Fa2/11,Fa2/12,Fa2/15,Fa2/16,Fa2/20
                               Fa3/44,Fa3/45,Fa3/46,Fa3/48,Gi1/2
I thought this command would return the MAC address of the device that was connected to that interface. Can anyone please explain the output of this command and what it might mean?

Thanks
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Commented:
very strange. what appen if you do a simple "show mac-address-table"?
Hi,

which switch are you using and what is the configuration of the port?

Author

Commented:
Its a cisco WS-C4503.

Here is the config:
sw1#sh running-config interface fa1/2
Building configuration...

Current configuration : 329 bytes
!
interface FastEthernet1/2
 switchport access vlan 345
 switchport voice vlan 765
 service-policy output autoqos-voip-policy
 logging event link-status
 speed 100
 duplex full
 qos trust device cisco-phone
 qos trust cos
 auto qos voip cisco-phone
 tx-queue 3
   priority high
   shape percent 33
 spanning-tree portfast
end
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Commented:
what is the inside address of core switch?

192.168.3.10 ?
hi

instead of
show mac address-table interface fastEthernet 1/2

try the old style of the command

show mac-address-table interface fastethernet 1/2

Author

Commented:
I get the same result with both commands
Don JohnstonInstructor
Top Expert 2015

Commented:
Please post the output of a "show mac-address-table"
Switch# show mac-address-table multicast vlan 1

Multicast Entries

 vlan    mac address     type    ports

-------+---------------+-------+-------------------------------------------

   1    ffff.ffff.ffff   system Switch,Fa6/15

the output of you command is the same as the multicast table. Maybe it's a bug in the ios. Which version are you using?

Author

Commented:
Hi,

it's 12.2(25)EWA14 release software (fc1)

Thanks
Don JohnstonInstructor
Top Expert 2015

Commented:
Please post the output of a "show mac-address-table"
Is the port up?
From the cisco website:
This example shows how to display MAC address table information for a specific interface:

Switch# show mac-address-table interface fastethernet6/16

Unicast Entries

 vlan   mac address     type        protocols               port

-------+---------------+--------+---------------------+--------------------

   2    0000.0000.0101   dynamic other                  FastEthernet6/16

   2    0000.0000.0102   dynamic other                  FastEthernet6/16

   2    0000.0000.0103   dynamic other                  FastEthernet6/16

   2    0000.0000.0104   dynamic other                  FastEthernet6/16

   2    0000.0000.0105   dynamic other                  FastEthernet6/16

   2    0000.0000.0106   dynamic other                  FastEthernet6/16


Multicast Entries

 vlan    mac address     type    ports

-------+---------------+-------+-------------------------------------------

   2    ffff.ffff.ffff   system Fa6/16

I think it's just showing you the multicast part because it hasn't learned any mac addresses on port fa1/2.
Don JohnstonInstructor
Top Expert 2015

Commented:
Is this the actual untouched output???

Those unicast addresses is from a Xerox OUI.

No it was just an example from the cisco website. I don't think the port has learned any mac-addresses so when he does show mac address-table interface fa2/1 it just shows the multicast section at the bottom.

Author

Commented:
The port is still flapping

Author

Commented:
Hi rochey2009,

I think you are right, the port hasn't learned any MAC address so its just showing the multicast part. I had someone go to the location where the switch is installed and found out that there is nothing attached to that port. Regardless, the port continues to flap. Its very strange.

Hi,

Does anything appear in the logs?

Author

Commented:
The port isn't bouncing anymore. Thanks for your help.

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