SIP traffic - minor issue with OPTIONS messages

OK, so the MSS nodes send their monitor traffic to the LB public VIP IP yes. So, the F5 won't respond on a servers behalf, it will send that monitor traffic to one of the two Rhino hosts and one of those hosts will respond (hopefully). This isn't an ideal configuration as your monitoring traffic is effectively being load balanced. I'd suggest you would be better off doing a simple tcp port check to the LB VIP (depending on the type); that will prove the VIP is up. For the path between the F5 and the Rhino servers, I assume you have monitors configured and working so you'll have the end to end flow covered.