gtm_add command...

What it the purpose for it?

You can run gtm_add to another F5's self IP as only as it can route and connect over SSH to that IP address, but you would never need to run to an F5's own Self IP.

Nor would it work, never tried it though, as gtm_add removes the local GTM/DNS configuration and pulls from group.

Need to sign some zone with DNSSEC. And after signing the zone with DNSSEC, it shows down