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Virtual Connect Ethernet Load Balance Policy for LACP Etherchannel and VMWare 3.5

Robert_266
Occasional Contributor

Virtual Connect Ethernet Load Balance Policy for LACP Etherchannel and VMWare 3.5

I have two Cisco 3750E switches in stack. A C-7000 enclosure with Bays 1,2,5,6,7,8 with VC-Ethernet modules. I'm using ports 5&6 in Bays 1&2 with LACP etherchannel trunks, (that's one set of trunks per bay). I have VMWare 3.5 on 5 BL460c blade servers. The load balance policy on the 3750e switches is set to src-dst-ip. I have the VMWare servers set to IP hash. Two of the 5 servers are making my vlan flap. If I change the virtual switch lb policy to failover the vlan flapping stops. I found a PDF that states the VC-E modules use src-dst-mac and/or src-dst-ip for load balancing the lacp etherchannels. How can they use both? Does anyone know how to force it to be just src-dst-ip? Why are the other 3 servers not flapping the vlan? (Since there are only two paths, am I just getting lucky src-dst-mac = src-dst-ip?)

Rob
4 REPLIES
HEM_2
Honored Contributor

Re: Virtual Connect Ethernet Load Balance Policy for LACP Etherchannel and VMWare 3.5

Rob, regardless of the load balance policy in VC or Cisco, you shouldn't be seeing flapping. What kind of flapping are you seeing? MAC Address flapping or port-channel flapping? Do you have an example of the console or log message you are seeing?

VC only supports LACP so your channel-groups on the Cat3750's should be channel-group x mode active or mode passive NOT mode on or desirable.

I think the VCE modules use src-dst ip when the traffic is IP traffic. When it is NOT IP traffic, then the src-dst MAC is used.

Robert_266
Occasional Contributor

Re: Virtual Connect Ethernet Load Balance Policy for LACP Etherchannel and VMWare 3.5

Yes, the channel groups are set to mode active. You are correct, if the traffic contains an IP header then the VC uses src-dst-ip. Here is a copy of the error message from the console.

840: 6d00h: %SW_MATM-4-MACFLAP_NOTIF: Host 0050.567c.e5fd in vlan 10 is flapping between port Po3 and port Po4.

Rob
HEM_2
Honored Contributor

Re: Virtual Connect Ethernet Load Balance Policy for LACP Etherchannel and VMWare 3.5

Robert,

ahh, ok. in VMWare ESX, you can only use IP Hash when all the VMNICs in a Virtual Switch connect to the same physical switch and the physical switch is configured for etherchannel or static 802.3ad. This is impossible in VC because each blade NIC connects to a different VC module on the midplane.

You can use load balancing, you just need to change the hashing algorithm to any other mode.
Lee Carey
Occasional Visitor

Re: Virtual Connect Ethernet Load Balance Policy for LACP Etherchannel and VMWare 3.5

Hi having a similar issue. Was this resolved by chaging the load balancing algorithm?

Thanks