Monday, March 17, 2014

Cisco Nexus: "%ARP-3-DUP_SRCIP_PROBE: arp [5622] Duplicate address Detected. Probe packet received from"

This was a little odd, but I found this message in a pair of Nexus 7000 logs:
%ARP-3-DUP_SRCIP_PROBE:  arp [5622]  Duplicate address Detected. Probe  packet received from

I found that this is common when connecting to other Cisco gear like 3750-Xs, etc.  See the below topology for this problem I was having (this is generic, but basically was it was):
What appears to be happening is that the 3750Xs are sending out some type of check.  Not sure exactly what at this point, as Im still researching it, but it sends these messages for device tracking.  The 6509E passes that traffic right on over to the Nexus (at layer 2, not 3).  So the Nexus doesnt like that for some reason and logs it.  TAC says its a compatibility thing, but Im not sure still.  
So here is what I did to fix it, on the 3750Xs, not the 6509E.  Nothing was done on the 6509E, only on the 3750X uplinks TO the 6509E.
3750X#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
3750X(config)#int gi1/1/4
3750X(config-if)#ip device tracking max 0

I did this on both the 3750Xs and this stopped the log entries on both Nexus devices.  I still need to find the reason this happens, but this is the fix so far.

For a 3850 switch you also have to configure this:
3850(config)# interface gi1/0/1
3850(config-if)# NMSP attach suppress 
3850(config-if)# end
3850# wr mem


  1. Thank you this fixed an issue I had with Nexus 7K and 3850's.

    1. Dinan, was your issue with DHCP NAK's / Bad Addresses, by any chance?

  2. Did you find out what could cause that kind of problem?


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