Okay I am running CER 1.3 , Call Manager 5.1.3 and several multiple WLCs with 1131ag accesspoints in our school district.
Recently we reconfigured our CER server to only look at ip subnets for classification of ERLs. Each school has it's own ERL and voice vlan(ip sibnet).
We have over 100 switches and the tracking engine was taking entirely to long. Also we are constanly move or switching out switches to support last ment growth and connectivty needs.
We designed it so that all of our 7920 phone use the same ssid and key to connect to wireless, enabling a user to take their phone to any campus and us it. The problem is where we have campuses that share a wlc. The use may not actually be tied to their voice vlan but may be ties to the other campuses voice vlan(subnet). So the phones are attached to the wrong subnet and will be routed out the wrong gateway.
option 1) re-enable switchtracking. But I belive that because all the traffic is being encapsulated from the ap bac to the wlc that the phone will still show up on the wrong ERL.
option 2) set the phone with a manual entry in cer. but when the user roams to a diffrent campus they would be in the wrong erl.
option 3) tell them not to call 911 on the wireless phone, but the people who have them are the most likely people to call. administrators, police, nurses, etc
I have about three campuse that share a wlc with another campus. currently have about 70 wireless phones deployed, with 80 to 90 more to put out.