DNS Last resort pool and irule issue

Hi

 

We have a pair of F5 with DNS/LTM features. We want to achieve an automatic page in case an application goes down. To do this, I use "last resort pool" in my DNS module (pool tab under wide ip). It works well except with an irule.

 

In case we need to access from internet, we configure 2 pools (one for Lan and one for Internet). So in wideIP we set an irule to give us the pool depending if dns request is from internet or Lan.

 

Here is the irule :

 

when DNS_REQUEST { if { [IP::addr [IP::remote_addr] equals 10.0.0.0/8] \ or [IP::addr [IP::remote_addr] equals 192.168.0.0/16] \ or [IP::addr [IP::remote_addr] equals 172.16.0.0/12] } { pool [string map {"_nat" "_int"} [lindex [pools -list] 0]] } }

 

If I set a last resort pool with this irule, the F5 always return me the DNS address of the last resort pool even if all pool are up.

 

Do you have an idea ?

 

Thanks