ESXi VMkernel Interfaces "vmk#" vMotion network fallback to APIPA IP address when set to DHCP config Causing vMotion failure

Products

• VMware vSphere ESXi

Issue/Introduction

• DHCP server is unavailable.
• One or more ESXi host has expired DHCP lease period.
• APIPA IP is being assigned to "vmk#" vMotion VMKernel adapter.
• APIPA IP reference range 169.254.0.0/16 to 169.254.255.255/16.
• One or more host still has the previously assigned DHCP address as they lease is not expired yet. For e.g. 192.x.x.x/24.
• "vmkping" fails between the hosts as the above will cause hosts to be in 2 different subnet.

Environment

VMWare vSphere ESXi.

Cause

vMotion vmkernel adapter is configured for DHCP, but its DHCP DISCOVER messages don't reach a functional DHCP server, or the DHCP server's OFFER doesn't reach the ESXi host, will result in an APIPA address being assigned

Resolution

• Make sure the DHCP server is available on the network and reachable from the ESXi host to complete the D-O-R-A process to get the IP address from DHCP server.
  • The DORA process is the four-step method DHCP uses to assign IP addresses: Discover, Offer, Request, and Acknowledge. A client broadcasts a Discover message to find a server, the server replies with an Offer of an IP address, the client sends a Request to accept the offer, and the server sends an Acknowledge message to finalize the assignment.
• If in case there is no DHCP server available in the environment, Make sure to use static IP address for the vMotion network.
• It is recommended to use static IP addresses for management-related VMkernel adapters such as Management, vMotion, and vSAN etc.
• To determine the communication issue, perform the packet capture using Packet capture on ESXi using the pktcap-uw tool

Additional Information

• If vMotion with APIPA IPs being assigned to all the hosts in cluster using same portgroup will still work as they they can still reach over layer 2. 
• Reference KB for the packet capture and analysis: Packet capture on ESXi using the pktcap-uw tool
• reference KB for How to troubleshoot DHCP issues: 373392