Impact of DNS failure on HA?

[JaySMX]

HA relies heavily on DNS, what will happen if DNS fails once HA is configured and functioning properly within a cluster? Will HA agents cache the IP information of other HA agents within the cluster for heartbeat functionality for a certain period of time? With a default of 1 second for heartbeats, the agents cannot be resolving DNS everytime they send out a packet. Is the time between DNS resolution of other HA agents based upon the DNS TTL value or another value within the host?

I'm reviewing a design in which the customer wants to put a local DNS instance on the vCenter server for ESXi cluster resolution and they expect HA to continue functioning should the vCenter server fail, which in this case will also take down DNS. I have not run into a configuration like this, I'm trying to determine exactly what will happen should the vCenter/DNS server go offline.

Thanks!

-Justin

[marcelo_soares]

Actually, HA agent inserts on the /etc/hosts file the reference for all hosts/IPs on the HA cluster, so if you loose the DNS server there will be no big deal. You should make a goods administration on this relation between the server and the hosts files to keep flexibility and stability on your HA cluster.

Marcelo Soares

VMWare Certified Professional 310/410

Virtualization Tech Master

Globant Argentina

Consider awarding points for "helpful" and/or "correct" answers.

[JaySMX]

Thanks for the reply! Is this documented anywhere? I looked at it appears that an IP of one of the primary HA hosts is added to the /etc/hosts file on each host.

If that's the case, should DNS be down while a primary failed would any hosts who are sending heartbeat packets to that primary be 'orphaned' from the cluster, for lack of a better word?

-Justin

[depping]

Check the ft_hosts file. It will contain all the name resolution info you would expect.

Duncan

VMware Communities User Moderator | VCDX

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