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Options for multi-site setup

Discussion in '3CX Phone System - General' started by SteveTheITDude, Jun 24, 2015.

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  1. SteveTheITDude

    Jun 18, 2015
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    Hey Everyone,

    I'm new to the 3CX world so please bare with me as these questions might seem easy for you..

    We are looking to replace our old Toshiba PBX's with some type of voip system. I've heard of 3CX for quite some time so I decided to try the free version, get some prepaid minutes with Flowroute and some used Yelink phones. I really like the ease of management and flexibility of the 3CX system however what I'm trying to accomplish is replace more than a single PBX. Ideally I want to have all offices interconnected so any staff can easily transfer an incoming call anywhere or dial directly to any phone (using DID's).

    A little background.. We have 29 offices total which are all connected by a full mesh site-to-site VPN (everything can communicate together). 3 of the larger offices have a dedicated Fiber connection (50MB x 35MB) while the other sites have a 35MB x 5MB cable connection. All sites are connected with SonicWalls (various NSA models).

    I've been doing some reading and I've come up with 2 options so far:

    #1 - (1) Central 3CX system that handles all incoming calls and then just distributes the call to the proper phone/extension. This would be great in terms of having (1) 3CX system to manage, however if the Internet drops at the location of the central 3CX system, I have 29 locations with no phone service..

    #2 - Setup multiple 3CX systems at the larger offices (with dedicated fiber) and then bridge the 3CX systems together. If one of the systems looses internet connection, our ISP should be able to route the calls to the other system for the outage.

    I also was wondering if an extension to extension call counts as a simultaneous call that would be applied towards the license? I.E I have a 4SC license, 2 extensions are talking internally and then I have 3 extensions that try to dial out to a public number, what happens?

    I'm just interested in learning more and how others would handle this type of scenario. I appreciate any feedback, thanks!
  2. lneblett

    lneblett Well-Known Member

    Sep 7, 2010
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    A call is considered to be:
    1. Extension to extension
    2. Extension to outside
    3. Outside to extension

    So, as an example, if one has forwarding set on their extension to go to a cell phone......when a call comes in this is counted as one call and when the system forwards it back out to the cell, this then becomes a second call as it is the system handling both legs of the call.

    As far as the topology, you will need to consider the number of extensions at each site and the impact of any outage. Also the bandwidth needed to carry any normal operational call levels as well as any emergency routing needs that may add to the normal. Each call, assuming a g711 codec, will occupy ~85Kbs in each direction. You will also want to consider your QoS options and how to protect the bandwidth for the voice calls so that it doesn't get trampled by the other data needs.
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