Grat.ARP on Nexus 7000

Hi we observed that if one of our Cluster is switching over( secondary is taking over the cluster IP adress) and sending Grat.ARP to announce the new MAC adress for the Cluster IP address, the Nexus does not update the ARP table based on a Grat.ARP.
I am not absolutely sure it seems if the Grat.ARP hits the HSRP active Switch than it works, if it hits HSRP standby switch it does not work.
Under vPC we have arp synchronize konfigured.
The only way how we can bring it to workmis to clear the arp table.
Any idea?
Thx
Hubert

Hi Hubert,
ok I see; but what about the cluster? Is it somehow related to vmware? which OS are we talking about?
I insist on this point as usually server administrators are not too much into networking and they might give misleading info. I.E. the vmware heartbeat that control the IP floating mechanism (which happens in case of cluster failovers) relies on ARP probes and not on GARP. The 2 are pretty similar but a N7K ignores it if it is not destined to the local IP (which it is true for the active hsrp member only). It flags it as invalid packet and drops it... you can verify taking the following before and after the switchover from both n7k
show ip arp statistics vlan
often you see increasing value if you have many hosts in the vlan... so the outputs of this command is not definitive in all cases.
Riccardo

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