GTM and Delegation of DNS

Hi Guys

 

I've been looking around at several posts regarding this (as its a common scenario) and some of it is confusing (for me as new to DNS). Wondered if the experts out there could help!!! :-)

 

Scenario is as follows; root domain of organisation=abc.com. A single URL (urla.abc.com) needs to be delegated to a pair of GTMs that will respond based on wide IPs. The wide IP is indeed defined as urla.abc.com. Specifically only a single URL is required to be delegated (with the potential for a few more later down the line).

 

My understanding so far is as follows

 

1) create a ficticious subdomain = 123.abc.com

 

2) create NS records for that sub domain.

 

123.abc.comNSGTM1.123.abc.com

 

123.abc.comNSGTM2.123.abc.com

 

3) Create A records that resolve the NS records to the two GTM appliances in question

 

GTM1.123.abc.comA1.1.1.1

 

GTM2.123.abc.comA2.2.2.2

 

Now here is where it gets a bit fuzzy.....

 

the original request was for urla.abc.com but i need to somehow force that to be answered by the 123.abc.com NS servers (the GTMs) so that the request for urla.abc.com ultimately hits the GTMs. I believe CNAMEs come into the equation but dont see how.

 

Any help/clarification would be most grateful.