The VSAN health check is giving errors about the MTU packet size.

Products

• VMware vSphere ESXi

Issue/Introduction

• The VSAN health check is displaying errors for: 
  VSAN:Basic (Unicast) connectivity check
• The VSAN cluster is not partitioned. 
• Pinging between the VSAN data nodes using the small ping test is successful

            vmkping -I vmk# <vSAN Node IP address>

                    (where vmk# is the vmkernel port (vmknic) used by vSAN)  

          Result : Packets: Sent = 3, Received = 3, Lost = 0 (0% loss)

• Pinging to the witness host from the VSAN date nodes using the small ping test is failing

           vmkping -I vmk# <vSAN Witness IP address>

                   (where vmk# is the vmkernel port (vmknic) used by vSAN)  

          Result:     3 packets transmitted, 0 packets dropped, 100% packet loss    

 

Note:  the VMkernel port (vmknic) being used by vSAN can be identified by running the following command on the host

esxcli vsan network list

Environment

VMware vSAN 7.x
VMware vSAN 8.x

Cause

ICMP was disabled on one of the firewalls in the physical network. 

Resolution

Allowing ICMP on the firewall resolved the issue. 

Additional Information

vSAN Health Service - Network Health - Hosts small ping test (connectivity check) and Hosts large ping test (MTU check)