I have to clear arp all of the time on a 3750. We have two vmware hosts. Each host has three NICs in them: one for service console, and two for failover. These are set up in a cluster. The problem is that when we move VMs from one system to another, we can't ping them anymore until I clear the arp table. All ports that the hosts connect to are configured with portfast, so it's not a learning issue that I can see.
What I did the other day is:
Moved the VM to the other server. Lost ping from my workstation to the server IP.
I COULD ping the server name from the 3750, soooo kindof tells me that the switch knows where the server is and it's updated it's table.
I COULD ping from the edge switch that uplinks to the core.
At first I thought it was because we had the subnet that we use for our workstations as a secondary address on VLAN1. I connected directly into the core from my workstation, and I couldn't ping it from a different VLAN, but I could ping it from the same subnet on a different server. I tried to clear arp on my workstation using netsh, and it didn't make a difference UNTIL I cleared ARP on the switch, and then it works fine.
It doesn't work to clear just the arp entry for the interfaces that are associated to the vmware server. I have to clear arp for the vlan that it's associated to.
Does anyone have any experience in what to do with this? I'm not even sure how to go about troubleshooting this any further.