PRI Cutover advise

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Mar 23rd, 2008
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Hello,


I have been tasked with handling a PRI cutover (we are getting rid of legacy PBX and going with a callmanager solution (with 2811 router with Vic2-2mft T1. I have minimal experience with routers/switches.


I understand how to configure the T1 for PRI (i.e. ISDN switch type, timeslots, framing, linecode clocking). But I'm worried about voice quality. I've heard some horror stories of echo, jitter etc.. when you take a PRI off a PBX and put onto a router T1 port.


Can you please let me know what types of problems I may encounter and the commands to remedy any problems that come up. I litterally will be unpluging rj45 from PBX and moving same connection over to 2821 gateway.


If I have problems, will the remedy need to come more from the Telco side? Or is all the responsibility on the router for correcting issues?


thank you very much in advance,


Victor



Correct Answer by paolo bevilacqua about 9 years 4 months ago

Hi,


voice quality for local phones will be perfect, do not worry about that.

There is a single test that would "audibly" reveal you have voip: make a call between two phones in the same room, go handfree with volume low enough not to get larsen effect. One talks and can hear the delay. That is the only thing that can "give you away".


Now for intra-site calls. Again, do not worry about quality first. Make the CCM work nicely in the hub, with happy users and all the issue solved, like how-I-do-that and hmm-it-was-different-before. If and when you've got trouble, write back :)


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gogasca Sun, 03/23/2008 - 23:48
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1. Gather all these details from Telco;

ISDN switch type, timeslots, framing, linecode clocking

2. Configure a loopback and then all router configuration so when you disconnect the PBX just plugin the cable and makes the interface in our side up and running...

3. VOice quality may depend on the other end...what will be the topology..etc etc

4. Check correct network-clock-participate/select config


5. Will open a TAC case to have someone on the line if something goes wrong since we dont know which issues you may encounter


Check:

http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080149a1f.shtml


victor2008 Mon, 03/24/2008 - 03:41
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Thanks for the quick response. topology is single location registered to CCM. Offnet calls will traverse single PRI (both local, ld and International common). There are also significant calls that will also traverse the WAN (to other locations that have CME and/or routers that connect to a legacy pbx).


When you say configure a loopback, just simply configure loopback 0 with an IP and bind h323 to that interface (we will be running h323 as gateway protocol for varios reasons).


thank you

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paolo bevilacqua Mon, 03/24/2008 - 03:58
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Hi,


voice quality for local phones will be perfect, do not worry about that.

There is a single test that would "audibly" reveal you have voip: make a call between two phones in the same room, go handfree with volume low enough not to get larsen effect. One talks and can hear the delay. That is the only thing that can "give you away".


Now for intra-site calls. Again, do not worry about quality first. Make the CCM work nicely in the hub, with happy users and all the issue solved, like how-I-do-that and hmm-it-was-different-before. If and when you've got trouble, write back :)


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