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Live Migration of Linux Guest Fails to Send a Gratuitous ARP and Loses Connectivity RRS feed

  • Question

  • I am having a problem with Linux guests that is hampering my ability to put a Hyper-V cluster into production.  For Windows guests, everything works fine.  Immediately after a live migration finishes, the guest sends a gratuitous ARP which takes care of setting up the FDB on the switch and updating the ARP table on the router.  The latter is especially important as we are using Broadcom nic teams which rewrite the MAC of outbound packets with the MAC of the active nic team member.  I have taken packet captures and can verify that the gratuitous ARP is sent.  The guest also sends a couple of ARPs with a source protocol address of 0.0.0.0 which I believe is a form of duplicate IP address detection.

    For a linux guest, no gratuitous ARP is sent.  Therefore, the switch and router are not updated.  Since the nic team is rewriting the MAC, all traffic is sent to the old host.  If I ifdown and then ifup the interface, this forces Linux to send a gratuitous ARP and traffic is restored.

    I have verified that this is not a problem with the nic teaming software.  I removed the teams on both hosts and repeated my testing.  The gratuitous ARP is still not sent.  Without the team, I don't have to worry about the ARP table on the router, but the FDB on the switch still has old data until traffic is sent outbound from the VM to refresh it.

    This is a serious problem for me, as I need to be able to host functional Linux guests.  I have not seen mention of this problem anywhere.  I have seen lots of people complaining about the Broadcom teaming software, but I have verified this is not the cause of the gratuitous ARP problem.  Furthermore, everything works great with windows guests.

    My working theory is that Hyper-V is instructing the virtual ethernet device to send a Gratuitous ARP after a live migration completes, and that there is a bug in the Linux integration components that prevents this from happening.  I am currently testing with Centos 5.5 running version 2.1 of the Linux IC.  My hosts are Server 2008R2 with all of the latest patches and recommended hotfixes.  I have tested with both emulated and synthetic adapters.  The adapter is connected to an external network, and the management operating system is not allowed to share that network.  A VLAN is tagged by Hyper-V.

    Friday, November 5, 2010 8:08 PM

Answers

  • Fixed in mainline Linux kernel and in the 3.1 release as well.
    This posting is provided "AS IS" with no warranties, and confers no rights.
    Wednesday, August 10, 2011 11:40 PM

All replies

  • Here is another person with the same problem:  http://social.technet.microsoft.com/Forums/en-US/winserverhyperv/thread/de7eb2cf-338a-49f3-980f-7dba6e9e1957

     

    Can someone at Microsoft confirm this?  Or anyone, really?  This is looking like a bug to me at this point, but if someone can pull some packet captures and confirm that their cluster does send a gratuitous ARP after migrating a Linux guest... I'd love to compare notes.  

    Tuesday, November 9, 2010 2:27 PM
  • Hi

    To Live Migrate Linux You need to set the MAC (Ethernet) address of the virtual machine to be static.

    Also, Select a host network adapter that supports this configuration and Remove the check mark for Enable virtual network optimizations on the virtual network adapter in the Hardware Configuration tab of the virtual machine to avoid the error 10696 : "The host network adapter does not support the specified virtual network adapter configuration".


    If this post is helpful, please mark it as such
    ________________________________________
    Alessandro Cardoso
    MVP | Microsoft Heroes | MCT
    blog: http://virtualisationandmanagement.wordpress.com
    http://virtualizacaoegerenciamento.wordpress.com
    Thursday, November 18, 2010 10:36 PM
  • I've done these things as well as everything else I can think of.  Everything is working except for the Gratuitous ARP not being sent when a Linux guest migrates.  Surely this is a bug?

     

    Any MS networking folks out there who can weigh in on this??

    Friday, November 19, 2010 2:47 PM
  • Mike Sterling, Linux Integration Services Program Manager is looking into reports of this issue, and they will reply back once they know where the issue lies.

    http://social.technet.microsoft.com/Forums/en-US/winserverhyperv/thread/de7eb2cf-338a-49f3-980f-7dba6e9e1957

     


    If this post is helpful, please mark it as such
    ________________________________________
    Alessandro Cardoso
    MVP | Microsoft Heroes | MCT
    blog: http://virtualisationandmanagement.wordpress.com
    http://virtualizacaoegerenciamento.wordpress.com
    Tuesday, November 23, 2010 1:20 AM
  • I've been in contact with Mike Sterling, and it looks like there there is a fix in the works.  I'll report back once I have more information.
    Tuesday, November 30, 2010 5:41 PM
  • Fixed in mainline Linux kernel and in the 3.1 release as well.
    This posting is provided "AS IS" with no warranties, and confers no rights.
    Wednesday, August 10, 2011 11:40 PM