We have several servers running Windows Server 2012R2 on top of VMware. In trying to diagnose some slowdowns we noticed that many of our servers are sending out lots of jumbo frames. This seems odd since jumbo frames aren’t enabled on any of the vm nics.
You can see that obviously we are sending out lots of jumbo frames and receiving a bunch too (albeit much much less).
…but the problem is that jumbo packets aren’t enabled in any of the virtual machines. How are they constructing the jumbo frames in the first place?
The ping screenshot is from the server with the most jumbo frames out to the server with the most jumbo frames in. You can see in the ping example that anything above 1500 bytes will fail. The 1472 byte payload (+ 20 bytes IP header + 8 bytes ICMP header) succeeds, but the 1473 byte ping fails.