PBX - GW integration

Unanswered Question
Apr 6th, 2007


if i want to integrate a pbx with a cisco gateway with either:

1: analog trunk then i will use fxo ports installed on the gateway side, but what should be the card (if any) be on the pbx for this analog integration?

2: or a ccs (BRI) then i will use (for example) vic2-bri installed on the gateway side but what should the card on the pbx be for this CCS integration?

please advise and thanks

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Paolo Bevilacqua Fri, 04/06/2007 - 08:20

1 - the card that is used for analog phone extension. I recommend you do not do that because you won't be able to receive digits for PBX (limitation of the PBX, not router), you won't receive caller number, etc.

2 - an ISDN BRI card, or QSIG card.

Hope this helps, if so please rate post!

user-cisco Fri, 04/06/2007 - 09:35

thanks but according to Q1 just to make sure:

i have router -> ip wan

and pbx -> to router and in the same time

pbx -> pstn

in other words the pbx has 4 direct analog telephone lines from telco as input and 16 extensions as outputs then what i have to do to integrate with the router (with fxo 4 ports) is to connect any 4 lines among the 16 pbx extension lines (outputs) directly to the 4 ports of router fxo?

am i right?

Paolo Bevilacqua Fri, 04/06/2007 - 10:15

Yes. Withstanding the limitations I mentioned above.

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user-cisco Fri, 04/06/2007 - 12:48

now, if this gateway is mgcp gateway and i want analog phones connected to this pbx to make outside calls through wan as first option and pstn through pbx as a second option i think the only option is to configure dial peers with prference vlaues for voip and pots dial peers

is this correct

are there any other ideas to accomplish this?


Paolo Bevilacqua Fri, 04/06/2007 - 15:31

mgcp implies callmanager in and is someway mutually exclusive to h.323 that works with dial-peers. make a simple drawing of all the devices involved and what do you want to accomplish so we can help better.

user-cisco Fri, 04/06/2007 - 21:54

ok, simply i have a branch site that has ip phones, and some analog phones which are connected to the this branch's pbx and this pbx is connected to 2801 gateway (fxo 4 ports) and also to pstn directly , while this gateway is connected to central site that has a ccm cluster,


i want anaolg phones in this branch site to make their intracluster calls through wan?

i want to configure mgcp as the gateway control protocol

now what config should be on this mgcp gw to make those analog phones in branch to make their calls as specified?

many thanks

Paolo Bevilacqua Sat, 04/07/2007 - 03:04


the problem is that the analog phones won't be able to use one stage dialing because you are using FXS on the pbx. They will need to dial a number first for reach the extension to which the router is connected (assuming you can trunk these extension in an hunt group), then receive dial-tone, then dial the number of the desired party. This is not user friendly, that is why you should use either E&M for analog and ISDN BRI for connecting to the pbx.

user-cisco Sat, 04/07/2007 - 03:25

hi p.bevilacqua

i wonder why i have to use a hunt group to dial the pilot number for this group while i don't need that in case of digital trunk? what is the difference?

and if so, where to configure this hunting?

can't dial peers with prefernces i may configure on the gateway be an applicable solution in this case?

can u explain more how does the call will flow in ur suggested solution?

many thanks again to u p.bevilacqua

Paolo Bevilacqua Sat, 04/07/2007 - 03:52


the problem with fxo/fxs on the pbx has nothing to do with the router, is a problem in the pbx, and has nothing to do with dial-peers etc.

When you have fxs ports on the pbx, these are extensions, each one has an own number. to call other sites via voip you will need to the pbx to configure a pilot number for an hunt group on these extensions.

When you use ISDN BRI instead, you already have two channels, true that if you have more than one you have to configure the PBX appropriately, but it is usually easier because these are seen as trunk lines on the pbx.


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