Guys,
RE GTM synchronization groups and GTM High Availability (HA) (Ver 11.x)
What explicitly is synchronised configuration wise in a GTM synchronization group ? Is this only the bigip_gtm....
The GUI menu differs depending on what version of Big-IP you have. For 11.4.1 and below, it's under Global Traffic / Listeners. For 11.5 and later it's under DNS / Delivery / Listeners
But in either version, all it does is provide a convenient and simplified interface to creating an LTM virtual that's already associated with the correct profile. You can go into Local Traffic / Virtual Servers after creating it, and it will show up there.
At that point, it's no different from any other virtual server. The virtual can have any address that falls within a subnet defined by one of the self-ips on the device. In other words, if you have a self-ip of 172.16.0.1/24, then your GTM listener can be any available address within that /24, including the self-ip itself.
Once the request is received, GTM processes it in the manner defined in the DNS profile (GTM / profiles / DNS ).
If there are no handlers for the query, and the listener happens to also be a self-ip on the GTM, then the request is sent to the local named (bind) process.