From the field: vMotion and Layer 3

So, when installing remote sites usually we end up with two nodes and for vMotion rather than using a switch we simply connect the ports back-to-back and we’re done.

Now recently we were configuring a remote site (part of a larger project) and the guys connected the server back-to-back for vMotion and it didn’t work, even we were not capable of pinging the VMKs of the vSwitches.

The only thing that actually worked was moving virtual machines across hosts but only when the machines were offline, when they’re online they reach 21% and get stuck (sadly I didn’t copy the error).

So apparently before the release of vSphere 6. vMotion required Layer 2 adjacency which was okay when connecting server back-to-back for vMotion traffic, and it seems that as at the release of vSphere 6 when connecting hosts in such a way for vMotion capabilities it doesn’t work.

Once we moved the ports to the switch (keeping the same configuration) and without configuring any VLANs vMotion worked properly without any issues.

I really don’t have any more insight on this, I will try to do more tests to extract more logs if possible but for now all I know is that back-t0-back vMotion doesn’t work =).