HA between GTM

Amr_Ali Do you mean having an HA device much like you have HA LTMs? If that's a yes you really don't have to do that because GTMs are inherently redundant for DNS because of how the sync works between them for DNS configuration. You might need them to be HA because they run multiple functions such as GTM, LTM, AFM, and so on but you should try and keep GTM off of the same box as those other services if possible.