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stecino's avatar
Icon for Nimbostratus rankNimbostratus
Mar 04, 2021

DNS Forwarding iRule on F5 GTM Listener


I currently have a GTM that answers for all the DNS queries. But what I want to do, is to be able to for particular zones, to be able to forward to external DNS server. Given that add those zones to Data group and match for those zones in the iRule, what would my iRule look like? I am specifically interested about the forwarding part

    set forwarded 0
    if {[class match [DNS::question name] ends_with forwarded_zones]}{




How can I explicitly set forwarding to specific forwarding IP or list of IPs in the forwarders list?

I am using 11.5.8 Version BIG IP software.

Thanks in advance

1 Reply

  • eey0re's avatar
    Icon for Cirrostratus rankCirrostratus

    To do this with an iRule, use the "pool" command to select the pool of nameservers you want to forward the query to. The query will bypass on-box BIND, and be proxied instead. This will need to be an LTM iRule attached to the Virtual Server, not a GTM iRule attached to a Wide IP.


    Another way to do this, without an iRule, is to define the zones in ZoneRunner as "forward" type zones, and let BIND do the forwarding for you.