Unstable connectivity behaviour on Hyper-V guests


Environment:

Windows Server 2008 R2 with Hyper-V Role

Symptopms:

 VMs on a certain Hyper-V host were having bizzare connectivity patterns, when I tried to ping other machines, I would get three types of ICMP reponses for the same ICMP request. below is a snapshot

 

The network configuration is shown below, with the stable and the unstable communication paths

 

 

Resolution:

1- disable netDMA on the Host NIC (check this article http://support.microsoft.com/kb/951037)

2- Disable Large Send Offload on the Host NIC (in the advanced properties of the NIC)

 


Comments (2)

  1. zarafeh says:

    Hello Phil, this issue was occuring for all networking protocols not just ICMP. With regards to the cause, it is hardware specific. This happens only for poorly written hardware drivers, and it is not a Hyper-V issue.

  2. Phil says:

    What was the caused the issue?  Was it related to the type of hardware or network adapter?  Did the network issues traverse other protocols beyone ICMP?