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Switchport mapping

I had to map the ports on a 2960 switch. I had to fill in the missing name on each port with the PC that connect to it.

This is a simple task that only require one command on the switch:

SWITCH#show mac-address-table interface fastEthernet 0/20
Mac Address Table
——————————————-
Vlan    Mac Address       Type        Ports
—-    ———–       ——–    —–
201    000f.2034.4b2f DYNAMIC     Fa0/20
Total Mac Addresses for this criterion: 1

I now hold the MAC address of the PC that connect to port 20: 000f.2034.4b2f

The next step is finding the IP address that match this MAC address. To find this piece of information I used my L3 switch that connect the 2960 switch.
This is the arp command to run on the L3 switch:

L3SWITCH#show arp | include Vlan201
Internet  192.168.201.101        26   000b.cdf5.b4e4  ARPA   Vlan201
Internet  192.168.201.100         7   0018.4d76.a2be  ARPA   Vlan201
Internet  192.168.201.103         5   0018.fe6b.187f  ARPA   Vlan201
Internet  192.168.201.102         0   0026.553e.050a  ARPA   Vlan201
Internet  192.168.201.105        78   000f.fe2e.290e  ARPA   Vlan201
Internet  192.168.201.104        82   000f.2034.4b32  ARPA   Vlan201
Internet  192.168.201.107        83   0014.c20a.11c3  ARPA   Vlan201
Internet  192.168.201.106        89   000d.9d99.12f4  ARPA   Vlan201
Internet  192.168.201.109        89   000f.20fd.4973  ARPA   Vlan201
Internet  192.168.201.108 4   000f.2034.4b2f ARPA   Vlan201
Internet  192.168.201.111        89   000f.fe9d.976d  ARPA   Vlan201
Internet  192.168.201.110        86   000f.fe40.d64b  ARPA   Vlan201
Internet  192.168.201.113         0   000f.fec8.6605  ARPA   Vlan201
Internet  192.168.201.112        89   0014.c20c.89f5  ARPA   Vlan201

Using include Vlan201 I cut the list to the single VLAN that connect to my 2960 switch, it is a good way to shorten the long list of every device in the network.
You can see that MAC 000f.2034.4b2f match the IP 192.168.201.108 and all I have to do now is run nslookup and get the machine name.

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  1. Roland
    May 24, 2010 at 2:44 pm | #1

    Or you can download FREE switch port mapper here:

    http://www.packettrap.com/download/index.aspx

    It has built-in dns name resolution, very useful.

    HTH

    Roland

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