vMotion migrations fail when using multiple VMkernel ports for vMotion in different IP subnets (2052092)

Symptoms

• When you attempt to migrate a virtual machine using vMotion and each of the VMkernel ports used for vMotion are in different VLANs or IP subnets, the operation fails.
• You see the error:
  
  The vMotion migrations failed because the ESX hosts were not able to connect over the vMotion network. Check the vMotion network settings and physical network configuration.
  
• When this issue occurs, the host has multiple VMkernel ports configured for vMotion.

Cause

There are two common scenarios that may warrant the use of multiple VMkernel ports for vMotion services:

• Multiple-NIC vMotion (introduced in vSphere 5.0): Multiple-NIC vMotion has specific requirements that must be adhered to for it to work correctly. In this case, all of the VMkernel ports configured for use with Multiple-NIC vMotion must be in the same IP subnet. If VMkernel ports are separated across subnets or VLANs, the service will not work correctly.
  
• Joining two separate environments with different vMotion networks: In this situation, a single host may have a VMkernel port in each of the two vMotion IP subnets/VLANs. If multiple VMkernel ports are selected for vMotion use, vMotion migrations may fail as the host can theoretically use either of the two VMkernel ports for vMotion purposes, and a connection may not be able to be established to the other hosts. The ability to select two VMkernel ports for vMotion purposes was introduced in vSphere 5.0 for Multiple-NIC vMotion purposes only.

Note: In ESXi/ESX 4.1 and earlier, it is not possible to select more than one VMkernel port for vMotion use.

Resolution

When using Multiple-NIC vMotion in vSphere 5.x, ensure that all VMkernel ports configured are in the same IP subnet/VLAN on all hosts. For more information on configuring Multiple-NIC vMotion, see Multiple-NIC vMotion in vSphere 5 (2007467).

Do not use multiple VMkernel ports that have been configured for vMotion for any purpose other than Multiple-NIC vMotion. When using a single VMkernel port for vMotion, all hosts participating in vMotion migrations must also have their vMotion VMkernel interface in the same IP subnet/VLAN.

Source:-

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2052092