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New Member

7920 ip phoes with 1131 ag access points and CER.

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.

New Member

Re: 7920 ip phoes with 1131 ag access points and CER.

Interesting question. Switch-port mapping will take precedence over subnet mapping regardless of the host, even an AP. Based upon the wording of your question you already know this as you are configured to only look at subnets. You are correct that CDP will not propagate so you would have to re-enable switchtracking/CAM table queries. Your other option would be to assign the APs to ERLs instead of the 7920s.


New Member

Re: 7920 ip phoes with 1131 ag access points and CER.

Hi Dennis,

Thanks for your input, however I don't belive that puting ap in ERl would work because the aps are lwapp only, there fore all of there traffic will be encapsulated and sent to the wireless controller where the controller would strip the encapsulation an place the it on the local voice vlan. There for the mac address shows up on the port channel going to the wireless controller. I have verified this by looking for the mac address of a phone and seeing it apear on the port channel for the wireless controller, not the ap.

Thanks again though for your input.


New Member

Re: 7920 ip phoes with 1131 ag access points and CER.


WLC and WCS. Could you use extension mobility and assign 7920s to buildings? Just a thought.


New Member

Re: 7920 ip phoes with 1131 ag access points and CER.



Re: 7920 ip phoes with 1131 ag access points and CER.

CER tracks wireless IP phones by IP address, and if the IP address is

found to be in a subnet assigned to an ERL, then that assignment will

take precedence over an manual assignment of line number or MAC address

to an ERL.

If the IP address matches an ER subnet - then that subnet will be used

to route calls. If the IP of the controller is used - then that will

remain unchanged when the phone moves to another location.

If a manual assignment is used - then that assignment is used regardless

of phone location.

In both cases, the ERL used will not change - when the phone moves from

one location to another.

At present the only way to work around the problem is to

make sure that the IP address of the primary wireless controller does

not correspond to any IP subnet configured to an ERL in CER. Then a

manual MAC or line number assignment to an ERL will take effect.

A more satisfactory solution for tracking wireless IP endpoints is

planned for CER 7.X I believe.

The solution requires that the wireless IP phone provide its

current location, or at least its currently associated AP, at call time.

New Member

Re: 7920 ip phoes with 1131 ag access points and CER.

gogasca.. valuable information, thanks for watching and posting to this thread. Dennis