vMotion between firewalls

Currently, I'm setting up a new VMware cluster as the exsiting hardware needs to be retired. The new cluster is in another management zone (and in another vCenter). To minimise downtime I looked at doing vMotion between the two clusters.

What I did was to disconnect one host from vCenter. Then add the host to the other vCenter directly on the ip number. The host was not added to the newly created cluster, only to the datacenter. And then drag and drop VMs between the clusters (EVC was enabled).

There was a couple of things that had to be tweaked before it worked.

vMotion had to be done between firewalls. When doing this, there are two important things to remember:

1. Set the default gatway of the vMotion interface (via vSphere Client)

2. Open inbound/outbound on port 8000 TCP in the firewall 

Furthermore, I encountered another issue. A number of VMs had a vmxnet NIC (it's some old VMs...). When starting to vMotion there was a warning that vmxnet is not supported on target host which is ESX 4 (source was ESX 3.5). However, after vMotion, the vmxnet NIC still worked. I tried to update VMware Tools and virtual hardware version to v7 and that also worked. vmxnet is kept as NIC after upgrade.