Switch assigning different IP address

bhasker22 · ‎09-24-2008

Hi,

We have a DHCP configured on Cisco 6513 switch and i found that one of the systems got the IP address as 10.155.0.6 which is nowhere related to our network.

My Troubleshootings:

- I checked the port and it is assigned the correct vlan of 105 as it should be

- however as it is getting different series of IP address other than 105 i have tried by disabling and enabling the port.

- Once i did that i immediately got the correct IP address of 105 series and the issue got resolved.

My question is why did the system acquired the IP address which is nowhere configured on our DHCP server and what are the possibilities and what should i check on the switch so that it will not be repeated again.

Waiting for your quick replies

Thanks in advance.

Regards

Bhasker

glen.grant · ‎09-25-2008

If it got an address that has nothing to do with your network then someone probably temporarily plugged in something that was setup as a dhcp server and handed out that address and then maybe realized it was causing a problem then pulled it off , see it all the time just dealt with the rogue dhcp server this week , these people bring in these home routers and stick them on the network and it can be a bear to find them .

Prashanth Krishnappa · ‎09-25-2008

Time to consider DHCP snooping

pndennie93 · ‎09-25-2008

Glen,

Have you developed a decent process for finding these devices? I had a bear of a time finding one last week. Thanks in advance.