vSphere HA isolation Address

[MohamadAlhousse]

Dears,

You know the recommendation for stretched cluster is to use two isolation addresses from each site for HA. But I need some clarification on the below point:

I know that when a host stops receiving network heartbeats, it will failsafe and start pinging the isolation address which is by default the MGMT network gateway to check if it is isolated or not.

Additional isolation addresses can be configured so that host will try to ping them if the MGMT gateway is not pingable.

However in my humble opininon, if the host can't ping its MGMT gateway, how can it ping the isolation address which is for example the site router IP address which may be in another VLAN? Will it still use the MGMT network to ping that isolation IP address? Do we need to add a static route on the host for that purpose?

Any clarification is highly appreciated.

Thank you

Regards,

Mohamad

[vmrale]

In my opinion You are right about MGMT inteface and static routes. The alternative is to create another MGMT interface in other VLAN/IP subnet.

Regards

[MohamadAlhousse]

vmrale​

Thank you dear, do you have any reference for detailed explanation about this configuration ?

I m not finding any details.

[vmrale]

Unfortunatelly I couldn't find any VMware's documentation, but the topic is mentioned incl. VMware vSphere ICM, VMware vSphere Design Workshop Student Manuals.

The clearest explanations but read/wrote between the lines You can find in Christopher Wahl's and Steven Pantol's "Networking for VMware Administrators"  and in Duncan Epping's "VMware vSphere 6.0 Update 2 High Availability Deepdive".

Regards

[MohamadAlhousse]

Thanks a lot dear,

I found this in page 48 in the vSphere HA deep dive book.

If a secondary management network is configured, this

additional address should be part of the same network as the secondary management

network. If required, you can configure up to 10 additional isolation addresses. A secondary

management network will more than likely be on a different subnet and it is recommended to

specify an additional isolation address which is part of the subnet.

So, as the additional isolation addresses are a recommendation in stretched clusters, so we have to design for multiple management networks when thinking about stretched cluster to be able to use additional isolation addresses. At least this is what I understand now. I wish I can see it implemented somewhere like this or stated in details.

depping​ Please can you clarify and confirm if the best practice is to use multiple MGMT networks when using stretched clusters to be able to add additional isolation addresses ? I hope you have more details about this in the coming "clustering deep dive" book.

Thanks a lot in advance,

Much appreciated,