GTM split DNS iRule

Greetings!

 

I was hoping you guys could scrutinize this iRule. The goal is to have the GTM return internal addresses to internal DNS queries and public addresses to public DNS queries. I also want to avoid having to create "internal only" VSs and Pools on the GTM. I have the following questions:

 

1. Will it even work?
2. What if all pool members are down?
3. Can you foresee any "gotchas"?
4. Can you make it better?

I would create a unique iRule for each WIP...

 

when LB_SELECTED { Check if the client source IP matches a private IP and also check which pool member was chosen. If the client IP is private and the chosen member server name contains "dal-" return the Dallas LTM VIP. If the client IP is private and the chosen member server name contains "ftw-" return the Ft. Worth LTM VIP.

 

if { ([matchregion ldns private]) && ([LB::server name] contains "dal-") } { host 172.10.20.6 } elseif { ([matchregion ldns private]) && ([LB::server name] contains "ftw-") } { host 10.10.20.6 } }

 

Environment:

 

• Active/Active data centers. One in Dallas, the other in Ft. Worth.
• A GTM and an LTM at each location.
• Each GTM has WIPs that point to pools that contain both a Dallas and Ft. Worth member (GTM configs are synced).
• Each GTM pool member has an Address (public IP) and a Translation (LTM VIP).
• Dallas LTM VIPs = 172.10.20.x. Ft. Worth LTM VIPs = 10.10.20.x.