Mar 27, 2026 - For details about updated CVE-2025-53521 (BIG-IP APM vulnerability), refer to K000156741.

Forum Discussion

Andrew_Wysocki_'s avatar
Andrew_Wysocki_
Icon for Nimbostratus rankNimbostratus
Apr 14, 2016

GTM iRule to set the pool based on which GTM is responding to query

I've been asked that when a DNS request comes into a GTM, that it responds with the GTM pool which is local to that GTM site if it's available. The setup is as follows, 2 DC's, a GTM at each, synced ...
application delivery
BIG-IP DNS
irules
Andy_McGrath's avatar
Andy_McGrath
Icon for Cumulonimbus rankCumulonimbus
Apr 15, 2016

So think you will need something like the following.

Your iRule using [whoami] returns the current user so need to use [hostname], this works on tclsh but not tested this directly on the iRule.

when DNS_REQUEST {
  if { ([hostname] contains "dc-gtm01") && ( [active_members www.site1.com_pool1] >= 1) } {
       pool www.site1.com_pool1
    } elseif { [hostname] contains "dc-gtm02") && ( [active_members www.site1.com_pool2] >= 1 } {
        pool www.site1.com_pool2
    }
}