Cat3550 ip address find

[Susan Taylor]

Is there an IOS command that will tell you what the mac-address and associated ip address is of a C3550 client?

[Peter Paluch]

Susan,

You can always use the show ip arp IP_ADDRESS command to display such a mapping but it depends on whether the switch has an up/up SVI interface in the same VLAN as the station, is able to IP-communicate with it and whether such communication took place at some time in the past.

Also, you can use the show mac address-table to see the MAC table contents associated with individual ports.

However, if the switch is performing only Layer2 switching and no Layer3 routing, then it is generally not concerned with IP addresses of the connected stations, and it does not build any L3/L2 mapping table.

Best regards,

Peter

[davy.timmermans]

I want to add to the great explanation of Peter that if you want to find the IP address associated with a MAC address you've to check on the default router for this client

You've to record first the MAC address associated with the port; eg for port 16

the show mac-address-table | i 0/16

If you've also a cisco-phone connected to this port, you'll retrieve 2 MAC addresses. Via the associated data vlan number you'll find which MAC to use.

Record this MAC address and go to the router/layer3 switch which is the default gateway for this vlan and issue the command

show arp | i

[Peter Paluch]

Davy,

Absolutely correct. Thank you for clearing up my response!

Also, most of the commands do not require using the | include directive, rather, they directly allow you to specify the argument you are looking for, e.g.:

show ip arp H.H.H ! where H.H.H is the MAC address

show ip arp A.B.C.D ! where A.B.C.D is the IP address

show mac address-table interface INTERFACE

show mac address-table address H.H.H

Best regards,

Peter

[davy.timmermans]

The pipes are a habit as you know, the show ip arp is a better command indeed

5 points for your clear posts