Emergency CID with hot desking

We have recently started using pj_sip extensions instead of chan_sip. Thanks to the pj_sip Max contacts feature, we are now able to have multiple endpoints logged to the same extension. This makes configuration and overall use much simpler.
Ex : Philip at extension 279 can have a deskphone, home deskphone, softphone all logged into 279.
We always have an Outbound Route flagged as Emergency for 911 calls. This uses the extensions Emergency CID and this was a perfect solution since multiple sites can be using the same standard CID but have different Emergency CIDs depending on their location. This is an issue though now that extension 279 can be logged into multiple endpoints at different locations.
I have checked out the Hot Desk Emergency CIDs that was recently added. This would be a great feature to base the Emergency CID by MAC address. However this currently only works for endpoints that are in a logged out state.

How can I have one extension logged into multiple endpoints, at different locations, with a different Emergency CID for each endpoint ?

Imagine if the Hot Desk Emergency CIDs worked for a logged in state, my issue would be solved.

I added support for subnet ID based caller ID in Always Be Conferencing – discussed in this other thread. It allows management of this option via internal Asterisk DB:

sirius*CLI> database put pngnpbx/abc/sbntcid/ 24 3035551234
sirius*CLI> database put pngnpbx/abc/sbntcid/ 24 3035552222
sirius*CLI> database put pngnpbx/abc/sbntcid/ 30 3035553333
sirius*CLI> database put pngnpbx/abc/sbntcid/ 30 3035554444
sirius*CLI> database put pngnpbx/abc/sbntcid/ 30 3035555555
sirius*CLI> database put pngnpbx/abc/sbntcid/ 28 7205550000

You might be able to extrapolate out that portion to suit your needs (although all of ABC is compatible with FreePBX.) See the AEL macro pngnpbx-abc-remote in ABC and related included Examples for more information.

Unfortunately basing the outgoing CID on the subnet used isn’t a solution. We offer hosted services. The phones are connected through Internet and it’s their public IP address that will be used. Most clients don’t have a static public IP address. So it can change anytime…

That’s why MAC address seems like the logical solution to me.

Might you consider adding VPN to the list of your hosted services ?

Every day more market participants are demanding end-to-end encryption, and I think one might be able to make profit by tunneling VoiP inside VPNs, particularly when intra-company calling.

If you configure the VPNs with very narrow subnets, and each customer gets N number of clients, then yes there’s some management overhead, but the subnet-id-to-caller-id could possibly work in that scenario.

I am not sure how much of a challenge that would be with soft phones.

Another idea would be to add dynamic DNS hosting, so each client device requires a helper app to run and update the name<->public IP mapping, something like “location123 . clientXYZ . pyoung . com” or “my-e164-did . clientXYZ . pyoung . com”

Unfortunately ABC does not (yet) support DNS host name to caller ID mappings…

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