iRule forwarding to Virtual Server not working

Hey guys

Got some news for you. I had conversation with the support. What I didn't know was that

log local0. "[virtual]"

only displays the current Virtual Server not the one the traffic is forwarded to. So my logging was not clear enough and I went down the wrong track the whole time. They gave me the hint to configure an iRule just for logging purposes on the backside VS. When I tried a request in my production environment no packets hit the backside VS, no logging visible, too.

I tried this setup on another BIG-IP cluster with no route domains and it worked out like a charm. I think my problem are the whole bunch of route domains configured on my legacy BIG-IPs. I asked the support whether there are options in iRules to say that the new VS is located in route domain xyz. When I have some news I'll write them down right here.