VMware Fault Tolerance Setup Error

I was recently tasked with configuring VMware Fault Tolerance on a pair of hosts in our network.  I checked out the VMware documentation and followed the steps/best practices but still had a bit of trouble getting FT to work.

Both hosts showed configured for FT and I could enable FT on the VM, but every time I tried to start the VM it would come back with an error “Could not start the secondary VM“. Checking the details in the “Recent Tasks” window I found the error description, “Virtual machines in the same Fault Tolerance pair cannot be on the same host“.  This error description a little boggling as both VM and duplicate were on different servers.  At least I had an error that I could research, so off to Google I went!

Sadly, the few articles I did find that referenced this error were very little help. I tried the troubleshooting steps from forum posts (resetting FT, live migrating a VM (and it working successfully), etc) but still got the same error when trying to start the VM.  I finally found the solution while testing the FT interfaces on both hosts.

What I decided to do was create a test VM and vSwitch.  The vSwitch would be set to my FT vlan (1000) and the test VM (WinXP) would have its nework interface set to the test vSwitch.  With a PC on my FT network I tried pinging both of my VM hosts.  Sure enough I didn’t receive a reply from either host.  So I checked the configuration on the swtiches each host was connected to and found there was no way the two hosts would communicate on vlan 1000.  I reconfigured the switches and did my ping test from the test VM, this time successfully.  I then started a FT enabled VM and voila, FT worked!
Hopefully this post will save someone a few days of troubleshooting!