GTM Topology/Source IP Based NAT

Summary of what we are trying to do:

 

 

Our current environment consists of Alteon GSLB's doing internal global resolution for a set of wide IPs. Our migration strategy is to modify the DNS delegations to point to the GTM (where they point to the Alteons currently) and have the GTM answer for any wide IPs configured there, and if not pass it through to the Alteon. The F5 and Alteon devices are not on the same subnet, so we need to NAT the client requests that pass to the Alteons (or do we?).

 

 

Now here comes the tricky part, we are currently doing source based GSLB for numerous applications on the Alteons. So what I was thinking was that I could create a group of static NAT's that match our current source based rules on the GTM and then update the source network rules to match the new NAT addresses. But can I leverage topology to select the NAT ip, or would I need to write an iRule to do it. Also is it possible to just forward the request to the Alteon without needing the return traffic to pass through the GTM (ie via Bind versus the local group we are using now).

 

 

The main goal of all of this is to bring the GTMs on-line in a gradual fashion to reduce the impact of any problems without affecting all of the globally load balanced applications.

 

 

I guess the other option would be to cable the Alteons to the GTMs and re-IP them but I would prefer to avoid this scenario.

 

 

Any thoughts?