VMK adapter doesn't respond handshake request.

Products

• VMware vSphere ESXi

Issue/Introduction

When performing packet capture at a VMK adapter, "SYNC" request is noticed, while "SYNC ACK" response isn't sent out.

Cause

The incorrect netmask at other vmk causes overlapping subnet. "SYNC ACK" response eventually is sent out from another VMK adapter.

Resolution

• Verify netmasks and subnets are configured correctly via route table.

esxcfg-route -l

For example: 

[root@esxi:~] esxcfg-route -l
VMkernel Routes:
Network          Netmask          Gateway          Interface
192.168.1.0      255.255.255.0    Local Subnet     vmk0
192.168.2.0      255.255.255.0    Local Subnet     vmk1
192.168.3.0      255.255.255.0    Local Subnet     vmk2
default          0.0.0.0          192.168.1.1      vmk0

This is a correct sample. No overlapping subnet.

[root@esxi:~] esxcfg-route -l
VMkernel Routes:
Network          Netmask          Gateway          Interface
192.168.1.0      255.255.255.0    Local Subnet     vmk0
192.168.2.0      255.255.0.0      Local Subnet     vmk1
192.168.3.0      255.255.255.0    Local Subnet     vmk2
default          0.0.0.0          192.168.1.1      vmk0

This is an incorrect sample. The subnet of vmk1 overlaps the one of vmk0. In such case, if a handshake request comes from 192.168.4.X/24 to vmk0, vmk0 will receive the request, while the response will be sent out from vmk1. 

• Edit incorrect netmask if there's any.

Additional Information

Japanese KB: VMK アダプタがハンドシェイクリクエストに応答しない