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New Member

How to find host address of a particular switchport

Does anyone know how I can audit the address, MAC or IP, of a device attached to a particular switchport?

5 REPLIES
Bronze

Re: How to find host address of a particular switchport

You do "show cam" or "show mac" depending on device OS to get the mac address off a switchport. Then you telnet into the gateway router of the vlan the switch port belongs to, and do "show arp" to get the IP of the mac address.

You can also use snmp to archive same goal. Please refer to following doc.

http://www.cisco.com/en/US/products/sw/cscowork/ps563/products_tech_note09186a0080094949.shtml#usertracker

New Member

Re: How to find host address of a particular switchport

Thanks for the response, Minie. This shows the MAC of the switchport itself, not the MAC or IP of the HOST connected to that switchport. I can SHOW INTERFACES, I think, and get the bia (burned-in address) of each switchport, but I have a rogue device on our network. I know its IP, MAC, and VLAN, but it has no hostname. I can find this device if I could only have a way to see the IP or MAC of the host connected to any switchport. Hope this helps. Thanks.

Bronze

Re: How to find host address of a particular switchport

That's my point actually. "show mac" WILL show you the host mac connected to that switchport. Once you get the MAC, do "show arp" on gateway router to get IP of that MAC. Then you know who the host is.

Did you have a look at the url I attached?

New Member

Re: How to find host address of a particular switchport

Thanks again for your reply. SHOW MAC ADDRESS-TABLE does show the mac address of the host I am trying to find. I do not believe, however, that it shows the port to which the host is connected, as it shows Gi0/2 which is a gigastack port connecting another switch to our Catalyst 3550. If I telnet to the switch that is attached to that port, and run SHOW MAC ADDRESS-TABLE, I see another Gb port that attaches another switch. This is almost like a TRACEROUTE command, but it never gets me to the port to which the host is attached. SHOW MAC only shows ports that attach two switches together. I know that the host in question is not a switch via two facts: one, it has gotten a DHCP address -- of course, all of our switches are statically addressed; and second, all our switches are accounted-for. None are represented by this IP. This weekend, I pinged the IP of the host, and it did not reply. Today, Monday, I pinged it and it did reply. This tells me that it is probably one of our client workstations, but which one I cannot tell. I have not looked at the article you indicated as we do not use SNMP here, and I am unfamiliar with its operation. It is hard to believe that Cisco does not provide some easy-to-use facility to query a switchport and return the IP/MAC of the host attached...

Bronze

Re: How to find host address of a particular switchport

Yes, if you don't know which switch the host is directly connected, then you have to do this traversing work until you find the correct one. That's why Ciscoworks has this function called User Tracking does exactly what you need.

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