Network Load Balancing and IPv6 Ping Timeout


  • I've noticed interesting behavior with NLB on Windows 2012 R2 and IPv6. I have two systems that use NLB on a Hyper-V cluster, each system is on a different node in the cluster. When I do an IPv6 ping within the same subnet, I notice that the reply time is normally 1-3ms, but every so often it goes to 100+ms. I also notice that both members of the NLB reply to a ping to the cluster IPv6 address. This is interesting.

    When I do a ping to the cluster IPv6 address from a different subnet, I notice that the reply is intermittent. The NLB nodes will either both reply to the ping or both won't. At first I thought that there was an issue with my network, but when I do a span on the ports that the cluster is attached to, I see that the IPv6 ping packets arrive, but the NLB nodes don't always send a reply.

    What is also interesting is that the NLB web farm I have setup seem to be working fine and is not intermittent, so this issue only has to do with ping. Has anyone else seen this type of issue, or is this a bug?


    Tuesday, July 08, 2014 3:11 AM

All replies

  • Hi Nathan,

    So are you running both IPV6 and IPV4? Do you have any clients that can't connect at all? Just on ping?

    The reason I ask is we had a server that was receiving IPV6 fine, but on receiving IPV4 would switch to IPV6 to connect SSL back to the client. Of course the clients never received it and just got a timeout. Funny thing is cell phones had no issue at all because they were straight IPV6. Only clients with both protocols got the timeout.

    So the ack was send back via the wrong protocol and nothing but the timeout is what the client sees. This may be an LLMNR issue. It came out from 2008R2 but think it may still apply

    Check this out:

    David Perkins

    IT Help Point, Inc.

    Sunday, July 13, 2014 3:38 PM
  • Hi,

    Yes, I'm running IPv4 and IPv6. Both local client and remote client can access the web resources that I'm NLBing with IPv6 and IPv4, so the system itself is working. The only odd issue is with IPv6 pings. I feel like NLB is just getting confused with ping and either has all cluster nodes reply or none reply. It isn't impacting service, but is very annoying.

    Thanks for the information.

    Sunday, July 13, 2014 4:46 PM