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New Member

calling from FXO ???


I have a question, just to confirm something, here is the scenario:

A customer has a connection between a 3640A router and a Definity PBX using Analog signalling: FXO ports in the Router, and Station lines in the PBX.

This 3640A router is connected to many 1751-V routers in a Hub&Spoke connection. In these remote locations there are FXS ports connecting directly to analog phones.

For I have done before, I know that the behavior of this network should be as follows:

1) The remote sites could call to the central site to an extension or to the PSTN.

2) The remote sites could call to the others remote sites as well (IP routing is being used - Full IP connectivity)

3) The Hub site users CANNOT dial to the remote sites because the central ports are FXO and those ports do not provide a dial tone. I think the only way the users form the central site can dial to remote sites is using static PLAR connections from each FXO port to a remote site.

For points 1) and 2) I am pretty sure it works, BUT the customer just told me that they can dial to the Spokes using FXO ports with other routers...

If this can be done ... do I have to configure something in the cisco voice-port OR in the PBX ???




Re: calling from FXO ???

If proper route plan/patterns are configured on the PBX, then it should work without any issues. Since that you say, it works with other others, I would suggest you to the signalling between the FXO and PBX. Although the FXO doesnt provide the dailtone, the 3640 should be able to route the calls to the remote locations provide the PBX passes on the called number to it. Check if it is doing that.

New Member

Re: calling from FXO ???


I would like to flag an issue with fxos and the fxs with the plar configuration

be careful of crosstalk when making interremote site calls : we are having a major issue with this problem .We have no fix for this to date

New Member

Re: calling from FXO ???

When the Hub calls to the extension where the FXO port of 3460 is connected this port opens automatically, giving the opportunity to mark the remote voip dial peer. Once the caller port (a telephon set connected to extension port or a call from CO line) is closed, the FXO port will close too, and so will remote the FXS port. You wont have any problems.

However, by definition you can use the PLAR connection to only one (and from only one) remote destination. Finally, you may experiment ring back problems.