Recently I received a question on twitter how the vSphere HA advanced option “das.isolationaddress” should be used. This setting is used when there is the desire or a requirement to specify an additional isolation address. The isolation address is used by a host which “believes” it is isolated. In other words, if a host isn’t receiving heartbeats anymore it pings the isolation address to validate if it still has network access or not. If it does still have network access (response from isolation address) then no action is taken, if the isolation address does not respond then the “isolation response” is triggered.
Out of the box the “default gateway” is used as an isolation address. In most cases it is recommended to specify at least one extra isolation address. This would be done as follows:
- Right click your vSphere Cluster and select “Edit settings”
- Go to the vSphere HA section and click “Advanced options”
- Add “das.isolationaddress0” under the option column
- And add the “IP Address” of the device you want to use as an isolation address under the value column
Now if you want to specify a second isolation address you should add “das.isolationaddress1”. In total 10 isolation addresses will be used (0 – 9). Keep in mind that all of these will be pinged in parallel! Many seem to be under the impression that this happens sequential, but that is not the case!
Now if for whatever reason the default gateway should not be used you could disable this by adding the “das.usedefaultisolationaddress” to “false”. A usecase for this would be when the default gateway is a “non-pingable” device, in most scenarios it is not needed though to use “das.usedefaultisolationaddress”.
I hope this helps when implementing your cluster,