GTM Listeners with NAT ?

Hi, We have inherited a GTM setup where the GTM listeners are configured with private IP (eg. 192.168.6.1) and in front of this we have FW NAT the public IP 123.456.6.1 to private IP of the listener. DNS subzone is then delegated to the GTM public IP and this works functionally.

 

Issue is that if the exterternal GTM is queries for it's own IP, eg. ns1.ext.gtm.com rather than return it's public IP it is obviously giving it's internal private IP. This causing a few issues.

 

How can we tell the gtm listener to present it's external IP to the world via DNS ? is it same like other GTM VS where you set the listener address to public IP and set a translation address ?

 

or does the GTM actually need to listen on a genuine public self IP without NAT ?