I have deployed Expressway C and E in my lab to try Jabber without VPN from internet. I can successfully login from internet. The problem is when I make a call to the client which is registered directly to CUCM, jabber is ringing, but I can't hear sound from both clients (using Jabber windows 9.7 for calling and called parties). My Expressway E deployment is using one leg with static NAT. I have open firewall from inside to public IP Expressway E and vice versa.
Also if I call from inside to Jabber Expressway, It will fail with service unavailable.error message from call history in Expresswawy C.
My topology looks like this:.
internet <--> firewall (apply static NAT to Expressway E) <---> Router <--> switch --- UCS server (Expressway C and E in same subnet)