For more information regarding the security incident at F5, the actions we are taking to address it, and our ongoing efforts to protect our customers, click here.

Forum Discussion

purna_256577's avatar
purna_256577
Icon for Nimbostratus rankNimbostratus
Oct 05, 2016

Need to know any possible way to clear cache/flush dns for a records on GTM/DNS where GTM act as forwarder for the query.

RX/vendor supplier changed the DNS records recently,We have situation where the TTL of DNS record expires in 86400 sec. BIGIP GTM is acting as forwarder for those records. When we clear cache on the ...
BIG-IP DNS
devops
security
John_Heyer_1508's avatar
John_Heyer_1508
Icon for Cirrostratus rankCirrostratus
May 03, 2017

Is the forwarder setup in Zones -> ZoneRunner -> Zone List? If so, it's using the BIND/NAMED backend. This TMSH command will restart it and thus drop all cached records:

restart /sys service named

You can also have the forwarder not cache at all by using the "forward only" option. Example:

zone "whatever.com." {
    type forward;
    forward only;
    forwarders {
        192.168.1.1;
        192.168.2.2;
    };
};

However, you probably wouldn't want to apply this to "." since that would disable caching for general queries.

Bottom line - whoever is controlling that records should consider lowering the TTL. 86400 seconds is 1 day, and most people are using 1 hour or even 1 minute.