MLAG with VMware or HyperV - tons of DUP packets

[Eric_Burke]

We deployed our first MLAG scenario with 2 x670's at the core and with VMware 6.0 downstream. We had unusual amounts of what appeared to be packet loss, overall slowness and VM's showing online, then offline, etc. A packet trace revealed a TON of duplicate packets and retransmissions. When we took the second peer offline, these ceased. We've since confirmed that both sides of each MLAG are using L3 algorithm (IP HASH on vswitch), we removed all unused / standby adapters from the vswitch and we ensured that beacon probing was off. We otherwise followed the 2012 white paper from Extreme on deploying MLAG in an ESXi environment. Not sure if all of the duplicate traffic is expected in this config or if we're doing something wrong. Ideas?

[Patrick_Voss]

Hello Eric,

Can you please provide the following outputs form both cores and answer the questions below:

• "show config vsm"
• "show mlag ports"
• "show mlag peer"
• What port# is the VMWARE host connected to on both cores.
• Are both connections on the VMWARE host setup as a lag.
• Are you using LACP?

[Eric_Burke]

We had to tear it down (at 4am to be sure we made the business day) so I don't have any "show" stats available. On the VMware side, we could not use LACP as this is not an enterprise plus client. We simply had two nics in a singe vswitch, both active, using L3 hash (although the whitepaper says any type is okay, a technote found on VMware says they must match and be IP based). Basically two 10GB nics, DAC connected to port 1 of each MLAG peer. All VLANs on the MLAG were on the ISC. End result was some VM's appeared offline but would then suddenly come online (via ping). That combined with the retransmits and dupe traffic had us concerned enough to drop the idea.

[Eric_Burke]

As a side note, when pinging devices from a downstream Extreme user switch (also connected upstream via MLAG), we received 2 responses for each ping (one labeled as DUP"). When we tried a two tier MLAG setup, we actually got 3 (two DUPs) per ping request.