When attempting to vMotion triggers vMotion vmknic is undefined. vMotion will attempt to proceed, but may not reach optimal performance warning, dedicate at least one physical uplink to vMotion to resolve this issue.

Symptoms:

• Attempting to vMotion triggers a warning message.
• In the VMkernel.log file, you see entries similar to:
  
  2014-03-11T05:18:25.349Z cpu1:8413923)Migrate: vm 8413926: 3267: Setting VMOTION info: Dest ts = 1394722258130795, src ip = <192.168.17.176> dest ip = <192.168.17.175> Dest wid = 0 using S
  HARED swap
  2014-03-11T05:18:25.350Z cpu1:8413923)WARNING: VMotionUtil: 5242: 1394722258130795 D: vMotion vmknic is undefined. vMotion will attempt to proceed, but may not reach optimal performance.
  2014-03-11T05:18:25.354Z cpu0:8413929)CpuSched: 583: user latency of 8413929 vmotionStreamHelper0-8413926 0 changed by 8413929 vmotionStreamHelper0-8413926 -1
  2014-03-11T05:18:25.355Z cpu1:8413923)Tcpip_Vmk: 1256: Affinitizing 192.168.17.175 to world 8413932, Success
  2014-03-11T05:18:25.355Z cpu1:8413923)VMotion: 2730: 1394722258130795 D: Set ip address '192.168.17.175' worldlet affinity to recv World ID 8413932
  
  
  

  Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment. 　
  
  
  
  

VMware ESXi 4.1.x Embedded
VMware ESXi 4.0.x Embedded
VMware ESXi 4.1.x Installable
VMware vSphere ESXi 5.0
VMware vSphere ESXi 5.5
VMware ESX 4.1.x
VMware vSphere ESXi 6.0
VMware ESXi 4.0.x Installable
VMware ESX 4.0.x
VMware vSphere ESXi 5.1

To resolve this issue, dedicate at least one physical uplink to vMotion. This is the VMware best practice.

This is a warning message and in most cases can be ignored. However, If you are experiencing vMotion failures or vMotion is taking a very long time then consider isolating the vMotion traffic to a dedicated physical uplink.

For recommended networking best practices, see vSphere vMotion Networking Requirements. These recommendations apply to all 4.x and 5.x versions of ESX/ESXi. With the advent of 10GB adapters multiple types of traffic can be routed through the same adapter, but should be separated by VLAN tagging.