GTM iRule split DNS

There's two types of iRules. GTM and LTM. A GTM iRule is attached to a WIP and operates at the WIP level. GTM iRules are pretty limited in what they can do (i.e. Only GTM stuff). So they're a bit of a subset of LTM iRules with the exception that they can get the pool member status of GTM Pools. (LTM iRules don't have access to GTM level information). I'm not sure GTM iRules can use data groups either...

However, even though GTM rules are pretty limited, because GTM is layer ON TOP of LTM, you can use an LTM iRule attached to the LTM VS that is created by GTM (You configure a 'listener' in GTM and that creates an LTM VS with lots of underscore in the name... You can attach LTM iRules to this VS to manipulate the traffic at the LTM level).

Using an LTM iRule gives you a much richer environment, as long as you don't want access to the list of pool members (VS's) in a GTM Pool. That's the approach this iRule takes. (For example, because GTM iRules and LTM iRules are different, I'm not sure you get things like functions etc in GTM iRules even in 11.4.1), I did have a discussion with a few of the F5 guys about GTM and LTM iRules and I think we came to the conclusion that GTM iRules aren't really very useful any more (In the old days, I think you didn't get the LTM level VS created, so pre v11 you were limited to GTM iRules or nothing. GTM doesn't really track LTM changes exceedingly well so I suspect they'll either drop GTM iRules entirely or merge the engines perhaps).

H