GSLB Split DNS by iRule

if clients sends dns A request not directly to f5 gtm, then we can use multiple cname method below which doesnt need irules.

as example for A hostname www.mycompany.com:
a. make external/public dns server to cname www.mycompany.com to www.externalgtm.company.com.
b. make internal/private/intranet dns server to cname www.mycompany.com to www.internalgtm.company.com.
c. in the external and internal dns servers: make f5 gtm as name servers for both domains externalgtm.company.com. and internalgtm.company.com.
d. add externalgtm.company.com and internalgtm.company.com into gtm zone runner's zone list.
e. create manual gtm vserver with public ip address (dependency can be set to relevant ltm vserver)

f. create 2 gtm wideip (www.externalgtm.company.com and www.internalgtm.company.com) then bind proper pools and pool members for them, i.e:
www.externalgtm.company.com gets pool members on public ip addresses,
while www.internalgtm.company.com gets pool members on private ip addresses