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ltp_55848's avatar
ltp_55848
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Oct 11, 2011

GTM - redundant or single

Hi All,

 

 

I'm certain I am overthinking this question, however; according to the GTM configuration guide when defining the Global Traffic Manager as a Server object, the GTM is to be defined either as a single or redundant system.

 

 

For an environment consisting of a HA pair of LTM devices, only one of which is licensed with the GTM module, should the GTM be defined as single or redundant?

 

 

Additionally, when defining the GTM, should one use the LTM self IP addresses, the GTM listener address, or a separate IP address?

 

 

Cheers,

 

  • George_Watkins_'s avatar
    George_Watkins_
    Historic F5 Account
    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?
  • George_Watkins_'s avatar
    George_Watkins_
    Historic F5 Account
    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.
  • George_Watkins_'s avatar
    George_Watkins_
    Historic F5 Account
    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.