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New Member

Voice over lease line using 3661 and 1751 routers

I have a 3661 routerat our central office with one slot empty and 1751 at two of our sites. The two sites are both connected to the 3661 running using lease lines and running 128K lease line.

We are planning to have two PBX installed at the two sites and inter connect this PBX to the current PBX we have at our central office using the 128K.

Can somebody advice me on the cards that I need to buy so that I can interconnect the PBX using the 128K lease lines and the 3661, 1751 routers we currently have.

Configuration example will be a bonus.

Need your help


Re: Voice over lease line using 3661 and 1751 routers

For interoperatability of Router with PBX (many vendors are given in the link) , check this link.

You will need T1/E1 voice wics on the 3660 to create a trunk connection between the PBX and router.

Sample configurations are also available in the sub links.

Cisco Employee

Re: Voice over lease line using 3661 and 1751 routers

Basically you want to use IP network for call (voips calls) between branch and central sites.

First we need to know the encapsulation that you are using for that 128k leased line. Now you want to plae PBX after the routers right? Means the 128k leased line will be terminated at router and not on PBX. So the diagram will be


In that case we need to know how many simultaneous calls max youmight need between branch and central office at a given time. Based on that we can suggest the modules on routers.

some examples can be found at

New Member

Re: Voice over lease line using 3661 and 1751 routers

Curerntly Im using the default (hdlc) encapsulation on the serial interface. We might need 4 calls simultaneously.


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