Friday, 14 October 2011

SBS2011 as VMware Guest Loses Router

Occasionally, on restarting SBS2011, after upgrade, I found that it had lost Internet connectivity. The connections to local devices were still perfectly good. I could ping other PCs, connect to shares, use and control network printers, but I couldn’t ping the router/gateway and couldn’t get through to the Internet.

I chased a few red herrings before I came across an article on the VMware forums somewhere referring to IP4 Checksum Offload. The article didn’t directly relate to VMworkstation 8 but it pointed me in the right direction.

Connectivity seems to be quite sensitive and if you face intermittent connectivity issues then here are a couple of recommended steps relating to NIC setup that worked for me.

1. Switch off Auto-negotiate, manually change connection speed until you make the connection, then switch on Auto-negotiate.

2. On all NICs, real and virtual, disable IP4 Checksum Offload.

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