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3850 stack problem - duplicate IP

codflanglers
Level 1
Level 1

I have a 3850 stack running ip services on version 03.02.03.SE of IOS-XE. I have multiple SVI's on the stack and getting duplicate ip address messages in the logs.

I have checked that the stack has come up properly and they are both reporting ready and are active/standby. I have recreated the stack a couple of times and each time its the same.

Any ideas? Bug maybe?

10 Replies 10

Reza Sharifi
Hall of Fame
Hall of Fame

Can you post the log messages you are seeing?

Do you have duplicate IP address anywhere on your network?

 

 

They are all like this:

Jun 30 13:55:41.568: %IP-4-DUPADDR: Duplicate address x.x.x.x on Vlan6, sourced by <MAC address>

The IP address of the interface is not used anywhere else on the network, as they were reserved for this building. The only place the IP address exists is on the SVI on the stack.

 

ok, find out what port this mac address is coming from, then go under the physical port and add this command

nmsp attachment suppress

then clear the log and test again.

HTH

The MAC address is actually coming from a port-channel. Tried adding the command but it made no difference.

Can you also add the same command to the other side of the Portchannel?

What type of device is connecting to this 3850?

It's on both sides of the port channel which is trunked. Does it need to go on the physical interfaces that are in that vlan?

Basically it's a 3850 stack running ip services connected to a larger 3850 stack running IP Base.

 

 

Yes, put the command on the physical interfaces and see if it makes a difference.

I have added this command on all the physical ports on both stacks. Still getting the duplicate address messages in the log.

Anything else I can look at? As I say, the stack looks fine and the IP addresses it is complaining about only exist on the SVI on the ipservices stack.

There is a newer version of IOS-XE that is recommended on the Cisco site. Should I go for this?

DOH! Fixed this. Turns out someone put the SVI on the ipbase stack thinking it needed to be there. Removed them and its now sorted. Thanks for the assist.

Hi, 

I have similar problem. Two switches WS-C3850-24T in stack, (IOS-XE Version 03.02.03.SE).

On downlik switches on uplinks we get this duplicate info message. 

After disabling IP Device Tracking (IPDT) with command: 

  • nmsp attach suppress

it helps:

IP Device Tracking (IPDT) Overview

http://www.cisco.com/c/en/us/support/docs/ip/address-resolution-protocol-arp/118630-technote-ipdt-00.html

Thanks for help!

Michal

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