12-05-2020 10:21 AM
This was a particularly odd issue which I had never experienced before so I thought it’s worth blogging about it.
During a normal MS Failover Cluster failover operation, the node calming the cluster roles sends out a GARP request to notify the networking infrastructure of the MAC address change. The Layer 3 switch / router then updates the MAC address in the ARP table and packets are routed to the node which claimed the cluster roles. Recently I found myself troubleshooting a MS Failover cluster deployment which wasn’t behaving quite in this manner.
Some background info:
So when the active node was A and I failed over the cluster roles to node B, the failover process was completing successfully however the 3 cluster IP addresses would stop pinging and wouldn’t start pinging again until an hour or so… if I reverted back to node A instantly, the pinging would start again.
Looking at the ARP table on the Layer 3 switch I realized that the MAC address associated with the cluster IP addresses wasn’t changing to the MAC address of node B – which is what we would expect as a result of the failover operation.
How to To enable “GARP reply” on Palo Alto
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05-19-2021 09:51 AM
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