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Problem with ARP

All,

We have an "issue" with ARP and VMWare. First of all, I know nothing about VMWare and I'm not the administrator of our VMWare servers, but I've been asked to see if there's anything we can do about this situation.

Sometimes VMWare sessions will move between servers, and this will cause the server to not respond anymore until we clear the arp table. Is there anything that can be done on the switch to make this more automatic? I don't want to really change the default timers for arp if I don't have to.

This happens pretty frequently too. I've been with the company for about a month, and we've had to clear it manually about 10-15 times because of this issue.

Thanks,

John

HTH, John *** Please rate all useful posts ***
1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Blue

Re: Problem with ARP

John

I know next to nothing about VMWare as well but it looks as though the mac-address of the VM does not change so no update of the arp tables is needed. What is needed is that the L2 switch needs to know that the mac-address has moved from one port to another. This is achieved by the vSwitch sending out a RARP packet which the L2 switch then uses to update it's forwarding table.

http://www.cisco.com/en/US/docs/solutions/Enterprise/Data_Center/vmware/VMware.html#wp697193

Sorry i don't have an answer but the above may point you in the right direction.

Jon

2 REPLIES
Hall of Fame Super Blue

Re: Problem with ARP

John

I know next to nothing about VMWare as well but it looks as though the mac-address of the VM does not change so no update of the arp tables is needed. What is needed is that the L2 switch needs to know that the mac-address has moved from one port to another. This is achieved by the vSwitch sending out a RARP packet which the L2 switch then uses to update it's forwarding table.

http://www.cisco.com/en/US/docs/solutions/Enterprise/Data_Center/vmware/VMware.html#wp697193

Sorry i don't have an answer but the above may point you in the right direction.

Jon

Re: Problem with ARP

I can always count on you Jon :-)

Thank you!

John

HTH, John *** Please rate all useful posts ***
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