duplicate address on switch

[suthomas1]

hello,

we saw following messages on pair of our core switches.

%STANDBY-3-DUPADDR: Duplicate address 192.168.2.5 on Vlan17, sourced by 0000.0c07.ac02

%STANDBY-6-STATECHANGE: Vlan10 Group 5 state Standby -> Active

%STANDBY-6-STATECHANGE: Vlan10 Group 5 state Active -> Speak

%STANDBY-6-STATECHANGE: Vlan11 Group 10 state Standby -> Active

%STANDBY-6-STATECHANGE: Vlan11 Group 10 state Active -> Speak

%STANDBY-3-DUPADDR: Duplicate address 202.88.87.54 on Vlan130, sourced by 0014.f15c.5a00

there are more messages similar to this on the switches. i have tried following cisco's documentation to check the causes but didnt help.

if we disconnect switch2 or some of its links from network, the issues goes off.

kindly help on finding a resolution to this.

thanks.

[fgasimzade]

Try to find the source of the duplicate ip address with show mac address-table address 0014.f15c.5a00 in switch2 to find the port, to which the causing device i connected. Check that device's IP address

[Antonio Knox]

192.168.2.5 (MAC: 0000.0c07.ac02) appears to be an HSRP virtual address.  Check the interface Vlan17 ip address and standby configurations.

For 202.88.87.54 (MAC: 0014.f15c.5a00), it appears to be a host on the network with the same ip.  Follow fgasimzade's advice and track down the mac using 'show-mac-address-table address 0014.f15c.5a00'.

[suthomas1]

Thanks to both fqasimzade and Antonio for the inputs. vlan17 is on group2 which relates to the mac we see in messages and 192.168.2.5 is the interface ip for vlan17.

the other host mac is still to be tracked. I will like to seek advise on what should be the next course of action, after tracking down the host mac and the previous hsrp mac's.

thank you.

[Antonio Knox · Accepted solution]

Do a 'show mac-address address MAC-IN-QUESTION'.  After that check the port that it is located on.  If that port from the output connects to another switch (you can verify this with 'show cdp neighbor [type slot/port]'), then log into the switch connected to that port and run the same command ('show mac-address address MAC-IN-QUESTION') again.  You will have to repeat this process until the port that displays in the output of the 'show mac-address' command above is either an access port or an interface.  At that point, you've found your duplicate.

I hope that makes sense.  If not, let me know and I can see if I can assist further.