LTM HTTP explicit forward proxy and route domains

Not sure if this answers your question but from:

https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/tmos-ip-routing-administration-11-4-1/2.html?sr=53367747

A route domain ID is a unique numerical identifier for a route domain. You can assign objects with IP addresses (such as self IP addresses, virtual addresses, pool members, and gateway addresses) to a route domain by appending the %ID to the IP address.

The format required for specifying a route domain ID in an object’s IP address is A.B.C.D%ID, where ID is the ID of the relevant route domain. For example, both the local traffic node object 10.10.10.30%2 and the pool member 10.10.10.30%2:80 pertain to route domain 2.

The BIG-IP system includes a default route domain with an ID of 0. If you do not explicitly create any route domains, all routes on the system pertain to route domain 0.

Important: A route domain ID must be unique on the BIG-IP system; that is, no two route domains on the system can have the same ID.

Hope that helps?

ps