RA Guard causes IPV4 fragmented packets to go missing

    General discussion

  • I have had this confirmed by a couple of sources on different Windows Hyper-V server 2012R2 setups.

    When RA Guard is enabled for a VM's NIC it causes the NIC to fail to respond correctly when packets are 1 - 7 bytes larger than the MTU.

    Dumping the traffic shows that the first fragment is received okay, but the 1 to 7 byte fragment is never received so the datagram cannot be reconstructed and dies.

    This is Guest OS independent.


         Ping hostname -l 1473 -n 1

         Request timed out.

    Has anyone else experienced this? Any solutions?

    Thursday, April 27, 2017 1:25 AM

All replies

  • Hi Sir,

    I also tested it in my lab (both hyper-v 2012 and hyper-v 2016 ) , same behavior .

    I'd suggest you open a case with Microsoft to get further assistance .


    Best Regards,


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    Saturday, April 29, 2017 6:06 AM