VMWARE Teaming across seperate cisco switches (not in a stack)

Unanswered Question
Jul 8th, 2009

Is it possible to have the VMWare and ESX Servers connected to two seperate 3750 switches (NOT IN A STACK) that in turn connects back to a core switch and run HA on the ESX VMWARE Servers?

I know you can do by running etherchannel from two cisco switches in the same stack but what if the two cisco switches were no in a stack and not possible to stack, can this be done or would there be an IP Address or ARP issue?

I have this problem too.
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Edison Ortiz Wed, 07/08/2009 - 05:10

No, it can't be done as the switch will detect the same MAC Address coming from the VMWare servers which will cause a flap on each switch's MAC Address Table.




cmelbourne Wed, 07/08/2009 - 05:13

thank you for the quick response on this.

I take it if the two cisco 3750 switches were in a stack and we had etherchannel or lacp to the ESX then it can be done or if the ESX goes into two seperate blades in a core switch it should be ok yes?

Edison Ortiz Wed, 07/08/2009 - 05:23

Correct. The issue is with the source device sending the same MAC Address via different switchports that aren't members of an etherchannel.

The stack allows you to etherchannel across different physical hardware (same goes for modular hardware such as 6500 and 4500) but you can't bundle 2 switchports from different logical hardware.

IIRC, VMWare allows some kind of feature where you don't have to etherchannel on the switches and the server can have dual links connected to the switch. Isn't that HA? I thought LB required the etherchannel while HA didn't. Haven't played with VMWare in years.

cmelbourne Wed, 07/08/2009 - 05:43

not sure to be honest with you as someone else deals with the VMWare bit.

The guy reckons the VMWare servers are not sending the same MAC address but send the same IP address and need to load balence

Edison Ortiz Wed, 07/08/2009 - 05:48

But HA != LB. I'm not sure how you are going to load balance without sending the same MAC Address.

I believe with HA, one server is sitting there on Hot Standby and kicks up the minute the primary server goes down.

If that's the case, you do nothing at the switches and the configuration is done at the server. It will work on separate switches.



cmelbourne Wed, 07/08/2009 - 05:57

thats a good point.

Going to push this back to the server guys and have a chat with them

thanks allot for this

Collin Clark Wed, 07/08/2009 - 06:07

We do it with 2960's. We have two switches in the top-of-rack both carrying the same VLAN. An EXS NIC goes into each switch. The team is active/passive otherwise you will get the MAC flap as Edison stated.

cmelbourne Wed, 07/08/2009 - 06:19

but thats not HA whereby the VM servers are active/active though. you have active/backup

Collin Clark Wed, 07/08/2009 - 06:27

Have mutltiple connections to your vswitch. I'm not a VM guy so don't take my word as gospel.


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