Duplicate ip address, how can I find involved devices

[rburkhard]

Hello,

Logfile of a router show duplicate ip address, with mac-address, vlan17.

How can I find out which devices or interfaces does has same ip address?

Regards

Ruedi

[Harold Ritter]

Go on the switch and do a "sh cam " to see what port that culprit device is connected to.

[rburkhard]

Hello,

It is a WS-C3550-24, no command sh cam available.

Ruedi

[jolmo]

Use "show mac-address-table address-table" in switch and "show arp" in router

HTH

[Georg Pauwen]

Hello,

if the duplicate IP address is real, the Windows client with the address will not be able to work, since Windows disables the NIC until the conflict is resolved. So I would check for a user that cannot work...

Not sure if you are running HSRP, but if you do you might want to check this link:

http://www.cisco.com/cgi-bin/Support/Errordecoder/index.cgi?action=search&counter=0&paging=5&query=STANDBY-3-DUPADDR

Regards,

Georg

[Georg Pauwen]

Hello,

it could also be an IOS bug. Which IOS and platform do you have ?

Regards,

Georg

[rburkhard]

Hello Georg,

WS-C3550-24-EMI , flash:c3550-i5q3l2-mz.121-8.EA1b/c3550-i5q3l2-mz.121-8.EA1b.bin

Regards

Ruedi

[Georg Pauwen]

Hello,

I checked for a bug with this IOS but there seems to be none. You might want to check for routing loops which could cause this, or spanning-tree issues.

Of course it could really be a duplicate IP address: if you are able to see the MAC address for the duplicate IP address, check this site to find out which machine type (manufacturer, e.g. IBM or Dell) is causing the duplicate (type the first four digits of the MAC address in the search field for public OUI listings):

http://standards.ieee.org/regauth/oui/index.shtml

Regards,

Georg

[Harold Ritter]

Ruedi,

Personally, I would start with tracking the mac address from the switch(es) and then proceed with the bugsearch if you can't find it.