PBX architecture advice


I am in the process of attempting to setup a small WISP and internet provision along with communications. I was wanting to see if my planned architecture is OK or will even work.

First off I was planning to create a PBX for each region of domestic customers and also have other systems to support some Businesses I am looking to provide VOIP services to. The Business PBX’s may have numbers that overlap with some of the regions or have numbers that I do not have region servers for. The regional servers will be located within the region they are to be deployed.

Due to this I was planning to create a “gateway” system that would be responsible for routing between each server and would also be responsible for connecting to the SIP provider.

I have a quick image to clarify what I mean.

I have done some initial tests and have been having issues routing calls from Business 1 PBX -> Region 1 PBX via the gateway PBX, one resin for not wanting to create direct links between each region is I would need to update the dialplan on each server each time a new user is added so planned to have this all handled by the gateway PBX. Another resin for using the gateway would be to optimise the SIP channels as usage of business and regional users would unlikely be the same.

If anyone has any recommendations on what would be the best way to layout the systems or any further information required please let me know



I would not use a ‘gateway’ host (or farm of hosts) if possible. Everything falls apart quickly if the gateway is not available.

I would register each regional or business host with the SIP provider for the DIDs they answer. I suspect your users can tolerate a simple edict ‘changes are distributed at the top of the hour’ and a cron job to distribute changes.

Similarly I would not depend on a single central database. I would replicate the routing database out to each regional or business host.

Also, while IAX rocks and has been my ‘goto’ protocol, I suspect you will find more expertise on this forum using SIP so be prepared to make a switch.

Thanks for the reply sedwards

I am relatively new to the deployment of PBX’s with most of my experience in network deployments but have been managing a few over the years, I assume the SIP provider will be creating an account with a number of “channels” for each PBX, rather than pooling the channels to be used on any of the systems or is this a decision i would need to have with the SIP provider.

Thanks again

Your SIP provider should allow you to configure each DID to either route to a specific server or route to whichever server last sent a SIP REGISTER request.

‘Channels’ is not a SIP concept. Your provider may limit the number of simultaneous calls, but that is their business model, not a SIP feature or setting.

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