CER 11 FXO

[David Harrell]

Hello,

Wondering if anyone can help me understand the configuration on CUCM for using an FXO port as the ELIN for an ERL. I've read the admin guide several times, but something just isn't clicking.

[dakeller]

David,

When UCM or CER uses an FXO port for placing calls to 911, the administrator does not have the ability to send a calling party.  So from a CER perspective, the ELIN is irrelevant to a call going out an FXO port.  The dispatch address for an FXO connection is typically set by the carrier.  FXO ports used by an enterprise are the same type of connection used at a residence with an analog phone (which is an FXO device).

Hopefully that answers your question.   

Thanks,

Dan Keller

Technical Marketing Engineer

[David Harrell]

Dan,

It does to a degree answer the question. We are interested in using FXO ports for the reason you mentioned. I'm not understanding how to connect CER with the FXO port at each of my sites. Also, not completely certain how to route calls to 911 through these FXO ports in CUCM. I have 13 sites that I need to accomplish this at, or let all calls come through our SIP trunks with the ELIN configured for the POTS on the site specific FXO, or main DN of the site.

[dakeller · Accepted solution]

David,

Since FXO connected ports are limited in functionality, you're going to find that practical uses for CER are also limited.  If you are interested in routing calls through CER to reach a specific GW, you have 2 choices.  The first is to use steering codes in CER.  So for calls to the FXO ports, the destination as 408911.  You then create a 408911 route pattern pointing to the FXO GW.  The other choice is to define the destination out of CER as 911 and use standard local route groups (SLRG) to route the call to the right FXO based on the calling device's device pool setting.

But the biggest limitation you're going to find with FXO is that it does not support E911 call back.  Since FXO ports do not collect called party digits, it's ASSUMED there is only 1 subscriber ID for the FXO.  With only 1 assumed DN for the FXO, you can only route inbound calls to one destination.  If this FXO is only used for emergency calling, then set the destination for inbound calls to the 913.ELIN for that FXO port.  CER will correctly process the inbound call and send the return call to the calling party.  But if the FXO port handles both regular and 911 calls, you cannot support PSAP callback because you don't have the ability to differentiate a regular call from a 911 call. 

Hopefully that clarifies how FXO works and the limitations that you have. 

Thanks,

Dan Keller

Technical Marketing Engineer

[David Harrell]

Dan,

Thank you for taking the time to explain this. It sounds like our best option here is going to be to route these calls out the trunks and drop using the FXO ports.