HA for DMZ ESXi 5.1 cluster

Virtualization becomes popular than never this year, I see many company is transforming internal infrastructure into virtual platform.

HA is key feature of vSphere ESXi 5.1, you have to consider this part on every design, especially DMZ virtual machine.


Most DMZ ESXi cluster has restricted networking policy, even ICMP maybe not allowed. As you may know, HA detects ESXi host alive by two parts: Storage and Network.

If host can see shared storage, it means host alive.

If host can ping default gateway, it means host alive.

What if ping is disabled on default gateway? You’ll get “vSphere HA agent on this host could not reach isolation address: xxx.xxx.xxx.xxx” on each host.

It can lead to VM lost HA protection sometimes, you could use following way to fix this problem.


  1. Login to each host by SSH.
  2. Run command “vmkping xxx.xxx.xxx.xxx” to ping any ICMP enabled IP address from vmkernal ports.
  3. Record ping worked IP addresses.
  4. Right click ESXi 5.1 cluster.
  5. Edit SettingvSphere HAAdvanced Options
  6. Add das.isolationAddressX, value is the IP address of step 3, X start from 0 to 9.
  7. Repeat step 6 to add all favored IP addresses.
  8. Add das.useDefaultIsolationAddress, value is false.
  9. Right click each host and select Reconfigure for vSphere HA.

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