Adding a second PRI

Unanswered Question
Jun 18th, 2008

Hey I am adding a second PRI to a router that already has a PRI configured and running.

The second PRI will be trunked together with the first one using the same DID range.

When the telco confirms that everything is ready on their side I want to test the second PRI to make sure it is working properly.

Is there an easy way to conduct a test to make sure my phone call uses the second PRI or is it generally ok to just let the telco add the additional circuit in and let them confirm that they can see it is up and running?

I have this problem too.
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Paolo Bevilacqua Wed, 06/18/2008 - 10:25

When they provision the circuit, keep an eye on it for the first hour or so. That is usually enough, no need to make provisions for you to be able to call on that circuit specifically.

phretbored Wed, 06/18/2008 - 10:27

Ok cool.

I just want to make sure that when I give them the ok that it is really ok.

I have worked on new circuit installs before but never one like this where an additional PRI is simply being added to an existing PRI.

Paolo Bevilacqua Wed, 06/18/2008 - 10:36

Well, the main things you want to check:

- circuit is clean of any error "show controllers T1"

- incoming calls are equally distributed on both circuits. "show isdn status".

- ditto for outgoing calls. This is exclusively your responsibility, not telco.

- You can disconnect any circuit and calls will use the remaining one, to resume normal distribution when circuit is back in service.

Thanks for the appreciation and good luck!

Michael Owuor Wed, 06/18/2008 - 10:36


To add to Paolo's expert opinion, you could test the outbound calls by pointing a test route pattern to the new PRI.

For inbound calls, your test might be different depending on the configuration of the PRI circuit. If it is expected that the telco will simply hunt overflow calls to the second PRI, then you would have to fill up the first PRI so that subsequent calls would use the second PRI. An easy way to fill up the first PRI would be to call IP phone_B from IP phone_A using its 10-digit (or 7, depending on your local calling patterns) number so that the calls are routed out to the PSTN and back in. Place the call on hold and place a second call. Repeat until the first PRI is full. Each call will use up two channels of the existing PRI, so you should max it out with about a dozen calls. Observer Q.931 debug output on the gateway during the test to verify the behavior you expect.

If the configuration is such that certain DIDs are associated with the second PRI, the test could be simply call one of those DID's.

Hope this helps.



phretbored Wed, 06/18/2008 - 10:55

Thanks all for the information.

I will be doing this tomorrow and/or friday and I will follow up at that time.


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