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DID Routing Between Two SoHo's


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Hi there,


I'm new to the Snom One / pbxnsip and so far I am impressed with the system. My background is Mitel and Asterisk coming from the IT realm.


A summary of the lab setup so far:


2 x Snom ONE SoHo's V2.6.9 connected via VPN, Head office hub site with one remote spoke site.

2 x Snom 320 Handsets V8.4.31 connected to each system, 4 in total at this stage. (Various softphones working also)

100 number DID programmed on head office SoHo. Full National Number 02904557xx (Sydney Australia)


The idea is to allocate a block of ten numbers to each remote site. So far I have the following extension numbering plan in place.

Head office extension range 5750-5759

Remote site extension range 5700-5709


Internal calls between systems using the 4 digit extension number function correctly. Inbound calls are also working using the DID's mapping to the head office extension range with the following regular expression.


Send call to extension: !([0-9]{4}$)!\1!5750


Outbound calling from the head office is also working correctly.


The two questions I need help with are:


1. How can I program the system so that inbound DID calls for extensions at the remote site match to the trunk for the remote site in the head office dialplan?


The call hits the head office SoHo and my SIP trace shows error 404 Not Found. I've tried both t and u in the regex but it will not match the extension to the trunk for the remote site. Is this a limitation of the system, judging from the Snom Online Book it is?


2. How can I program the system so that outbound calls from the remote site are pushed to head office and out the DID trunk?


Calls come into the head office and again error 404 is the result. The regex used on the headoffice inter-system trunk is

!([0-9]{10})!\1!t! !([0-9]{8})!\1!t!

so any 8 or 10 digit number should be matched to the dialplan wildcard (*) entry sending calls out the DID trunk.


The two systems are not using the same domain name, however I have over-riden this using the domain setting within the trunk programming so the remote site's SIP Invite shows the correct domain in the From field.


I could include alot more information with SIP traces etc... however I'd like to know first if this is possible before delving deeper.


Any assistance with this is greatly appreciated.

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The core question if you want to use the HQ PBX as a pure router. Check if a SIP proxy would do a better job, and especially stay out of the media path to minimize the delay. And this would also give you the possibility to route calls internally for local PSTN breakouts.


If you decide to keep the setup, you should try to avoid trunk-to-trunk calls, it is easier to use trunk to extension calls and extension to trunk calls. The trick is to register the branch offices to the HQ: On the branch office you use a trunk, and on the HQ they appear as a extension. Then for incoming calls, you can send the calls to the right branch office by assigning multiple DID numbers (alias names) for the HQ extension. There is a special flag in the domain that tells the PBX not to change the from/to-headers, so that in the branch office you can still use the To-header for routing the call to the final destination.


The other alternative would be to forget about the two-tier setup and register all office directly with the service provider. Internal calls can be done through the public network essentially by using the diaplan for the short numbers and replacing them with the right, global routable telephone numbers (e.g. pattern: 55xxx replacement 0203234343*). This setup would work better if the telephone costs for the internal calls are not an issue.

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