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Francois_Dumais's avatar
Francois_Dumais
Icon for Nimbostratus rankNimbostratus
Mar 04, 2014

Is it possible to have GTM enabled on F5 LTM boxes arranged in an active-standby redundancy mode?

I read that having GTM enabled on an F5 LTM active-standby setup could cause problems in relation with DNS delegation. Is it possible to configure the setup in such a way as to avoid problems? We need to have a LTM+GTM enabled in order to do DNS load balancing towards monitored servers.

 

Thanks

 

application delivery
BIG-IP DNS
deployment
design
LTM

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  • Mohamed_Lrhazi's avatar
    Mohamed_Lrhazi
    Icon for Altocumulus rankAltocumulus
    Mar 04, 2014
    Can you clarify : - What the "DNS delegation" problem is? - GTM is for global load balancing... I think LTM alone is enough to do DNS load balancing... Can describe further what you need to achieve?
  • Cory_50405's avatar
    Cory_50405
    Icon for Noctilucent rankNoctilucent
    Mar 04, 2014
    I think what is meant by DNS delegation issues is that typically a parent zone will be configured with NS records to each authoritative name server at the child level. So there would be an NS record for each GTM. If one of these GTMs was active and one standby, half of the queries (theoretically) would be coming to the standby GTM.
  • Francois_Dumais's avatar
    Francois_Dumais
    Icon for Nimbostratus rankNimbostratus
    Mar 04, 2014

    What I want to achieve is the following : we want a DNS-like functionality that would return an IP addresse based on a positive monitoring for a node e.g. if the monitor detects a positive condition on an html page, then that's the IP address returned by the DNS-like functionality. We have LTM, but how do we implement this DNS capability within LTM?

     

  • Mohamed_Lrhazi's avatar
    Mohamed_Lrhazi
    Icon for Altocumulus rankAltocumulus
    Mar 05, 2014

    You should check with your F5 sales engineers... am not sure how licensing works, but DNS related iRule events and commands might be present in LTM or LTM plus some DNS feature, but surely in GTM indeed.

     

    https://devcentral.f5.com/wiki/iRules.DNS_REQUEST.ashx

     

    With iRule dealing with DNS events, plus LTM pools and custom monitors, I imagine you could achieve that.

     

    With GTM, you would either make GTM authoritative for your entire domain, so it intercepts all requests, or delegate some some subdomain where these "special DNS names" would live....then configure GTM to answer DNS requests for A records based on the health status of the web servers...

     

    Note that pricing wise standalone GTM appliance is probably the same as the software addon module for LTM... so it would be cleaner to think of GTM is an independent appliance that handles your DNS requests and uses its knowledge of the LTM appliances virtual servers to answer accordingly....

     

    Question: So, you have a DNS name that you need resolved to the IP of the web server that is UP? Why not put all those web servers in a pool behind the LTM, and let DNS resolve the name to the IP of the virtual server?