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Alex Pfeil
Rising star

IP Device Tracking and Gratuitous ARP?

I ran into the IP device tracking issue where clients/servers were seeing duplicate IP addresses. My question is, would turning off gratuitous ARP resolve the issue? It seems to me like the server sends out an ARP packet and receives a response from my switch. Is that what is causing the issue?  I have seen posts where people are disabling IPDT with nmsp attach suppress, or ip device tracking maximum 0.

How would turning off gratuitous ARP on a layer 2 switch effect the network?  It seems to me like we really don't need or want gratuitous ARP on, and that would also resolve the duplicate ip address detection problem. I look forward to any comments.

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Mark Malone
VIP Mentor


i havent tested this so i cant be sure but reading your post and checking against others it looks like a similar issue is known and there is a workaround , the link i provided earlier shows something related

Known Issue

The 'keepalive' probe sent by the switch is a L2 check. As such from the switch's point of view, the IP addresses used as source in the ARPs are not important: this feature can be used on devices with no IP address configured at all, so the IP source of is not relevant.

When the host receives this messages, it replies back and populates the destination IP field with the only IP address available in the received packet, which is its own IP address. This can cause false duplicate IP address alerts, because the host that replies sees its own IP address as both the source and the destination of the packet; refer to the Duplicate IP Address Error Message Troubleshoot article for more information about the duplicate IP address scenario.


Then it links off to this document explaining the duplication further


A user post also discusses it on the forum , linking that doc



is this what your seeing or is it something totally different in logs ?