irule for DNS traffic

Hi ,

I have a irule and i already tested it my infra. 

You have to configure Topology first in GTM(like below region(EMEA,NORTH_AMER,..)

please note - i mentioned "Body" in some "else if", it means you have to fill if-else ladder inside that "elseif" like elseif(with actual pool). Please configure proper pool with matching location. 

here if active member in your pool is greater than 1 only it fill forward traffic to a VIP. So there will be no down time :)

when DNS_REQUEST {

  #log local0. "- (Request) Client: [IP::client_addr] - Request: [DNS::rrname] - Type: [DNS::rrtype] - Topology: [whereis [IP::client_addr]]"

if { [matchregion [IP::client_addr] EMEA] } {

if { [active_members pool1 ] >= 1 }

{ pool pool1 }

elseif { [active_members pool2 ] >= 1 }

{ pool pool2 }

else { pool pool3 }

}

elseif { [matchregion [IP::client_addr] NORTH_AMER] } {

if { [active_members pool5 ] >= 1 }

{ pool pool5 }

elseif { [active_members pool6 ] >= 1 }

{ pool pool6 }

elseif { [active_members pool7 ] >= 1 }

{ pool pool7 }

else { pool pool8 }

elseif { [matchregion [IP::client_addr] SOUTH_AMER] } {

               Body

}

elseif { [matchregion [IP::client_addr] OCEANIA] } {

              Body

}

elseif { [matchregion [IP::client_addr] MIDDLE_EAST] } {

              Body

}

elseif { [matchregion [IP::client_addr] ASIA] } {

               Body

}

else {

              Body

}

}

any help?

you dont need irules for this purpose.

set the dns pool lb method to topology
then use topology config to set request from japan to prefered datacenter

https://techdocs.f5.com/en-us/bigip-15-0-0/big-ip-dns-load-balancing/using-topology-load-balancing-to-distribute-dns-requests-to-specific-resources.html#GUID-C0726318-48C8-4514-8852-74586A4AF97F