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Basic Cisco Emergency Responder question

I'm fairly familiar with CUCM and prinicples of IP Telephony but I'm very green with CER.  I have a CER server at HQ that covers a building with 3 floors and about a dozen zones.  All of the route patterns to support this have been setup in CUCM and a contiguous block of DID numbers was set aside a long time ago specifically for CER/E911.  Everything works fine with E911 at HQ.

Recently a remote office came into play.  The remote office has 3 or 4 users.  There's only 1 physical IP Phone (for general use).  Everybody there will use IP Communicator.  All of the VoIP traffic is passing across a VPN tunnel.  PSTN calls from this location use a SIP trunk at HQ.  I have a couple of questions.  First, is it reasonable to route 911 calls across the VPN tunnel to utilize voice gateway resources at HQ?  Second, if we do that can a new zone be integrated into CER for this remote office such that calls originating from the remote office will go out to the PSAP via HQ and the PSAP will show address information for the remote office (assuming that all of the paperwork is done with the provider/PSAP)?

Chris Deren
Hall of Fame Master

Sending 911 calls from centrelized location should only be considered if the SIP provider support e911 functionality and can route the call to local PSAP center where the phone is located. You would need to define different ERL/ELIN for those sites in CER.  If that is not an option your only option would be to deploy local POTS lines for 911 calling.



hi Chris,

Does L3 provider in US support E911  ?  so that we can implement centralize CER.

- what is the terminology to tell provider, so they can route particular ELIN to local PSAP center?

- we only have 1 Cisco CER with one SIP trunk in HQ which serves 25 sites (we want all 25 sites to use CER at HQ and same SIP trunk in HQ), possible ?



K, I can not speak for L3's capabilities as it's been a while since I've worked with them. Some SIP trunk providers can provide ALI database updates and others do not and then you need to rely on 3rd party such as Intrado/West, RedSky, 911ETC, etc. You need to check with your provider if they can provide "Location" information as designated in the MSAG government database instead of just street address. Almost all sip trunk providers advertise their support for e911, but in their mind it means they can route calls sourced from central data center to remote PSAP which is not really E911 unless they can also provide the exact location as defined in CER.

Thanks Chris,

Just clarify.  

- If Telco is able to provide "Location" info , then even we use HQ DID, call can still route to other cities local PSAP ?

- is the "Location" you mean here is similar to ESN?



No, you cannot use different site's DID range to route 911 calls as the telco will deliver the calls to another PSAP as they route 911 calls based on the caller ID, unless you bring in 3rd party provider i.e. RedSky and route 911 calls to them instead. I don't know what ESN is, but location is a field in MSAG (think master government street database) which usually identifies specific location within a building, i.e. NW corner 3rd floor.

If Telco can use "Location" in ALI database then different site DID will work?

As I explained, NO, because the telco company that routes the call does not use this field to make routing decision, they route the 911 call based on the caller ID presented. The location field is only used by 911 center (PSAP) or 3rd party i.e. RedSky.

Ah I see,thanks

I thought before ,ALI database can do it, with statement below:

"Some SIP trunk providers can provide ALI database updates and others do not and then you need to rely on 3rd party such as Intrado/West, RedSky, 911ETC, etc"



Think about ALI updates as independent item from actual call routing. Lets assume that L3 can provide ALI updates, what that means is there have a way for you to define the Locations in either a portal they provide or a document of some kind, that information is fed into the ALI/MSAG database so that the detailed can be shown the 911 calls is made. The actual call routing across the L3 SIP trunk would still route the based on the caller ID, unless they state they actually do the lookup when they route the call, that would be a question for them. RedSky for example can route based on the location field, so you can assign a block of DIDs for the ELINs from let's say the HQ location and they assign them as you wish to individual locations, since the 911 calls would route either via dedicated RedSky sip trunk or you transform the 911 call to designated RedSky DID and route it to them over other provider's trunk.

Thanks Chris,  L3 got back to us and said that is possible with RTN, route to local PSAP and  show correct address.

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