Cross vCenter VM migration fails with the error "Cannot connect to host"- VMware vSphere

Products

• VMware vSphere ESXi 7.0
• VMware vSphere ESXi 8.0

Issue/Introduction

This article addresses the issue of VM migration failure between vCenter servers using advanced cross vCenter migration. The migration process fails at 37% with the error "Cannot connect to host." 

Environment

VMware ESXi

Resolution

1. Verify Network Connectivity:

Ensure that the vMotion and Management networks between the source and destination hosts are reachable with vmkping.

2. Check Port 902:

1. Verify that port 902 is open via the TCP protocol.
   nc -vz <HostIPAddress> 902
2. If the connection fails, then the port is possibly blocked. 

TCP port 902 must be open for both UDP and TCP protocols for vMotion to function correctly.

3. Open the TCP port 902 on Firewall rules

4. If port connectivity (902, 443, 8000) is verified, investigate the VMkernel routing configuration. Run esxcli network ip route ipv4 list from the ESXi host command line to ensure the default gateway for the vMotion/Management stack is correctly configured.