GTM - redundant or single

If GTM is only licensed on one of the boxes then it would be a single system. When you're defining the GTM you'll want to use the self-IP address. GTM uses iQuery (UDP/TCP port 4353) to gather and distribute sync group information. Port 4353 should never be accessible from a listener IP unless that listener IP is also a self-IP (most people don't do this). Hope this helps,

 

 

-George

Thanks George,

 

 

So the GTM will be added as a single system using it's own self-IP and the LTM pair (of which the GTM module is licensed on one only) would be added as a redundant pair but using a separate self-IP. Correct?

If you are adding the LTM to be monitored by the GTM (and use discovery, etc.) then the LTM would indeed be a redundant system. I'm not sure about using a separate self-IP or if they could use the same as they are querying different information. Try it both ways and post your results.

 

 

-George

Thanks George. I was re-reading a section of the GTM Configuration Guide and came across the following:

 

 

Note: If your installation of the Global Traffic Manager resides on the same system as a Local Traffic Manager, you define only one BIG-IP server. This server entry represents both the Global Traffic Manager and Local Traffic Manager modules.

 

 

Unfortunately, this doesn't really clarify anything, as when adding the GTM/LTM the argument could be made either way for adding the system as a single system (single GTM), or as a redundant system (LTM HA pair).

 

 

However, if I add the GTM/LTM as a redundant system, then I'm assuming that this will be taken as an implication that the GTM is a HA pair, which may have unexpected consequences if the system were to fail.

 

Shamelessly bumping this thread in the event anyone can clarify how a LTM HA pair with one unit singly licensed for GTM should be added as servers.

Sorry I wasn't more help.

 

 

After thinking about it further I would try adding an additional self-IP on the GTM/LTM unit and use one for the GTM and the other for the LTM. That way you can add the LTM pair as redundant without conflicting with the IP of the GTM.

 

 

The Achilles' Heel is that even with an active/standby setup you still have a single point of failure if the unit with GTM fails. The GTM listener will follow the Active unit so you won't be able to failover to the LTM-only unit without losing GTM functionality. You may be better off running as a standalone or purchasing the GTM license for the second unit.

 

 

-George

Thanks George. I've run with the setup you suggested of a separate self-IP address for the GTM although I've had the alternate configuration suggested through the official support channels. Unfortunately, although I'd like to license the second unit, my employer is not able to justify the expense.

 

 

I had thought about separating the LTM pair into a single LTM and GTM but have judged that maintaining LTM HA is a higher priority for our environment.