New Install Architectural Question

[netelligence]

Greetings all.

In the past with Asterisk systems when there has been a Main location and multiple branch locations in different cities, I have put phone servers with analog or digital phone line gateways at each location and then each server manages calls that go between branches.

I'm doing a new install and replacing such a system. My question is if it is possible/advisable to have only 1 phone server with analog or digital phone line gateways at each branch to connect to the respective branch's local telephone company. Having 1 central server would solve some issues that the company wants to do, but I've never had a pstn gateway traverse across a WAN on different subnets before.

Each branch is connected to the main branch by either a dedicated line (T1 grade or higher) or a site to site VPN.

Because of the type of business, we still need to use local lines rather than simply VOIP providers.

Thanks for your thoughts.
L.

 

[tom_ch]

Why don't you use the 3CX Bridge?

 

[netelligence]

I'm prepared to put in 3CX servers at each location and bridge them together and that is the type of config I'm used to. I'm just trying to check out the feasibility of using one central server instead. I just didn't know if anyone has tried this using separate gateways across the WAN with only one server at the main location.

Thanks,
L.

 

[tom_ch]

you can use a central server, by placing the SIP Proxy Manager in each satellite location.
The point is, when the central server is down, all branch offices can't make phone calls, too

 

[ian.watts]

I just utilize a site-to-site VPN from remotes to central.. and run the voice traffic over that. Data is already running over it anyway.

I have also used a SIP ALG on the router and configured remote extensions instead.. either way. Could bridge.. would need multiple systems and thus multiple licenses. Depends on your loads and available connectivity, I suppose.

 

[jed]

Hi

I read it as netelligence ask, if anyone have been using a Central placed 3CX configured with FXO´s that is placed at there branc offices to reuse existing analog lines. The Central 3CX will use each branc office´s FXO gateway for in and outgoing calls.

To me this seems possible with ex beroNet´s FXO Gateways if the local router is forwarding correctly. However there will be double traffic on the line. Calls comming in on the FXO, going to the Central PBX and return to one or more remote users at the branc office.
I did not try this setup myself, but have customers with same old setup. They decided to instal a Central 3CX for all there Danish offices (moving all numbers to a common SIP Provider) and they placed a Bridged server in another country with a ISDN Gateway to be able to call at a very low cost in that arrea. They got rid of 6-8 Asterix servers, and their users were very happy for there new and improved phone quality

/Jesper
http://shop.jed.dk

 

[jpillow]

You can use one central server and connect via SPM to each location, site to site, direct extensions as mentioned by all here. If your main point is to save money as a license at each location well thats attainable you just have to determine what would be the best fit based on your comfort level, skill, and network.

 

[bardissi]

This scenario is practically what we do almost everyday.

We host 95% of our customers and the other 5% is on prem.

For the 95% that we host out of the cloud we are using an SBC (session border controller) which makes the remote phones so simple.

The SBC is put in place of the SIP Proxy Manager when you go to provision phones from the 3cx management console.

So yes centrally placed server is viable.

PM me if you want more info.

 

[netelligence]

Thanks for all the replies. Very useful information.

Jesper is correct. I'm simply looking at the possibility of creating a central server and using the each remote branch's FXO gateways for in and outgoing calls.

It is not so much to reduce price on licensing as it is to have central control on one server rather than 8. Also to allow more flexibility as far as creating ring groups and possibly queues that span across different branches.

I've never tried, but is it possible to create a ring group that includes extensions from another 3CX box across a bridge?

Thanks,
L.

 

[infonetics]

We use hardware IPSec VPNs with a central server with no issues. Makes management of the extensions really easy since they're within the same network (technically).

I take that back, we have had one issue, multicast paging isn't supported by the IPSec standard. But, these locations don't do much paging, so extension pages work fine. Would really like to make multicast work properly in remote locations, however.

 

[bardissi]

Why deal with the mess of gateways when you can just covert all your did's to sip and than have remote phones off the pbx instead.

Why deal with VPN overhead when you could just route that voip phones direct? Unless you need the VPN for other reasons non phone related its not neccessary.

Also, you can create paging group that do not use multicast via 3CX Ring Groups which would solve that issue.

 

[infonetics]

Why deal with the mess of gateways when you can just covert all your did's to sip and than have remote phones off the pbx instead.

Why deal with VPN overhead when you could just route that voip phones direct? Unless you need the VPN for other reasons non phone related its not neccessary.

Also, you can create paging group that do not use multicast via 3CX Ring Groups which would solve that issue.

The VPNs are in place for other applications anyway.

Ring group paging can take a very long time to connect, depending on the number of extensions, and we've noticed some delay/echo between different models of phones. Multicast has been much quicker, and less latency.

 

[bardissi]

Best practice is to have same model of desk phones in as many places as possible.

Understood on VPN in place for other things.

I have been able to get sonicwall to pass multicast traffic across VPN but its a lot of work.

Ring group paging has been good for us.

 

[infonetics]

I just realized I misread the question in the first place, regarding having the PSTN lines still come in at the branch locations. I would recommend going pure SIP at the central location, and serving the branch phones across VPN.

 

[bardissi]

Well at least we agree on going all sip ; )

 

[ian.watts]

Yes, that is what I would recommend. We assign "local" DIDs for calls made from the remote offices in order to better have their local customers/contacts call.. instead of calling some 503 number to Portland.

There is a bit of payload on the VPN traffic.. you can choose a fancier method to fling the bits to your central office otherwise.. but if you have the bandwidth at the remote locations, should flush out.

I was dealing with a remote office in San Francisco proper.. the available circuitry bandwidth in that down is "poor" at best.. was prioritizing traffic for RTP in order to keep the calls sounding right.