Technical Forum
Ask questions. Discover Answers.
Showing results for 
Search instead for 
Did you mean: 

GTM DNS ReverseLookup



Hello everyone!!

I was curious as to how the GTM gslb functions when executing a reverse lookup. I have a gslb url that fetches two ltm vips when I perform a nslookup, but when I try to perform a reverse lookup on the IP received, nothing like a failed result appears.

Is this the gslb via GTM default behavior? or something not configured as is?



Community Manager
Community Manager

Hey  @ashk - I see nobody has answered this yet. I'll pin this to the top of the forum over the weekend to give your question better visibility. 


Forward and reverse looks have nothing to do with each other.   If luck the F5 GUI might add a record, but it does not mean things will work.  Have a look under

forward lookup:  DNS> zone>zonerunner>resource records: view = external (unless you use split DNS),  names = FQDN domain, type=a/aaaa , names = host name/Wide IP names.      you should see "0" TTL records if the Wide IP is defined. 

forward lookup  DNS> zone>zonerunner>>resource records: view = external (unless you use split DNS),  names =   you see PTR type records if things are defined.   RDATA = FQDN. 

dig/nslookup   FQDN F5-ip to test forward   - i.e. nslookup 

dig/nslookup  q=ptr (IP address in reverse).in-addr-arpa.  F5-ip to test reverse 

i.e. nslookup -q=ptr    (might have the incorrect syntax here)

For forward lookup the domain above you need to define you as a subdomain using NX records.    Same for reverse but is probably your IPS or who you got the IP address from is the DNS holder.  I think you need a BGP AS number for this setup.   i.e F5 the owner of  *  would need to define NX record for “162” then then in thay zone can the PRT recodes be defined.

I assume you talking about public DNS and not a private DNS.      


seems like DNS "A" records missing for the 2 VS IP addresses in local DNS. please add and test

if not please share output