01-14-2008 12:54 PM - edited 03-03-2019 08:15 PM
Hi everyone,
I was wondering how I can find out the actual physical interface a MAC is learned on instead of the VLAN interface.
For example, on my switch I have:
show arp
Internet 192.168.0.25 - 0018.bad3.cb41 ARPA Vlan2
Internet 172.16.1.25 0 0009.0f06.ff0c ARPA Vlan3
The VLAN interface doesn't tell me which physical port it came out of...
Is there a way to find that out?
Thanks in advance.
Ali
Solved! Go to Solution.
01-14-2008 01:07 PM
Ali
You need to look at the mac-address table eg.
DC-BBP-F00-DS2#sh arp | include 000e.7fb4.f819
Internet 10.231.199.43 3 000e.7fb4.f819 ARPA Vlan40
DC-BBP-F00-DS2#
DC-BBP-F00-DS2#sh mac-address-table address 000e.7fb4.f819
Legend: * - primary entry
age - seconds since last seen
n/a - not available
vlan mac address type learn age ports
------+----------------+--------+-----+----------+--------------------------
Supervisor:
* 40 000e.7fb4.f819 dynamic Yes 10 Po1
As you can see the actual interface this mac-address was learned on is po1 which happens to be an etherchannel connection to another switch.
HTH
Jon
01-14-2008 01:07 PM
Ali
You need to look at the mac-address table eg.
DC-BBP-F00-DS2#sh arp | include 000e.7fb4.f819
Internet 10.231.199.43 3 000e.7fb4.f819 ARPA Vlan40
DC-BBP-F00-DS2#
DC-BBP-F00-DS2#sh mac-address-table address 000e.7fb4.f819
Legend: * - primary entry
age - seconds since last seen
n/a - not available
vlan mac address type learn age ports
------+----------------+--------+-----+----------+--------------------------
Supervisor:
* 40 000e.7fb4.f819 dynamic Yes 10 Po1
As you can see the actual interface this mac-address was learned on is po1 which happens to be an etherchannel connection to another switch.
HTH
Jon
01-14-2008 01:23 PM
Let me put it in another way to add to Jon's great example:
Show arp will tell you which layer 3 interface has the address.
But the info you want is at layer 2, so you need a layer 2 command, show mac-address-table exactly.
01-14-2008 03:53 PM
Thanks to both replied - very helpful in understanding the difference between the two commands.
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