ESXi 5 Host Isolation

What is a ‘host isolation’?

It’s the term that VMware use to define when an ESXi host is no longer able to communicate with specific IP address’s and therefore it is deemed to be isolated from the rest of the cluster.

By default the ESXi hosts default gateway (the VMkernal gateway) is used.  Depending on your infrastructure this is normally a Layer 3 switch, router or firewall.

Whats the problem with that you ask? Well what happens if you have an outage of your Layer 3 switch, firewall or router? Well vCentre will think that your ESXi hosts are isolated and depending on your ‘host isolation response’ perform one of the following actions:

The recommended action for vCentre 5 is to ‘leave powered on’.

We therefore need to provide more external devices for vCentre to communicate with before it invokes a host isolation response. To do this we go into the Cluster Settings > vSphere HA > Advanced Options.

We then add additional IP address’s that we went vCentre to communicate with in the following format:

das.isolationaddress1 10.0.0.1
das.isolationaddress2 192.168.1.1

We then end the range of IP address’s with ‘das.usedefaultisolationaddress’ ‘false’

What IP address’s would I recommend you use in a production environment?

– vMotion/FT switches
– SAN Controller Management IP address’s
– Layer 2 Switch
– Layer 3 Switch
– Firewall

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