Multiple PRI Groups on single T1 interface

[ShailendraK]

Hi All,

I have come across a situation where another equipment is being replaced with a Cisco 2821 router with VWIC2-1MFT-T1 card.

The previous equipment is configured to receive voice calls on first 10 channels but sends back any voice calls only on the remaining channels.

Is there a way to configure the same on the router like some sort of pri group where the pots dial-peer could be made to point to some sort of group or even if it is possible to force a dial-peer to use one or a particular group of challels?

I am interested in any solution and it is urgent.

Due to the urgency I will be folling any replies and test them throughout the weekend so any help will really be greatefully appretiated.

Many thanks in advance for any help.

Shad

[Kenneth Mohammed]

Hello,

Basically the command to do this is:

controller t1 x/x

ds0-group 0 timeslots 1-10 type e&m-wink-start

ds0-group 1 timeslots 11-24 type e&m-wink-start

Then on your outgoing dialpeers configure:

dial-peer voice 1 pots

destination-pattern 9[2-9]......

port x/x:1 (remaining channels for outbound)

forward-digits 7

dial-peer voice 2 pots

destination-pattern 91[2-9].........

port x/x:1 (remaining channels for outbound)

forward-digits 11

Hope that helped, if so please rate.

[ShailendraK]

Hi Ken,

Thanks for the reply. I will be reaching work in about 3 hours time. I will post back the result immediately after testing.

And I will make sure I rate your responce.

Thanks for the help matey.

Regds,

Shad

[paolo bevilacqua]

Kenneth,

In your answer, you assumed the OP has CAS, while I've assumed it has PRI.

In reality we don't know what he has, so that should be clarified.

[paolo bevilacqua]

You do not need multiple trunk groups to achieve the above.

First of all, the router has no control on which channel it receive calls.

To limit the number of outgoing calls, just configure max-conn 20 unde the outgoign DP.

[Kenneth Mohammed]

Hey Paolo,

Thanks for the clarification. I did assume CAS T1 since he was saying that he had some channels dedicated for incoming while others were dedicated for outgoing. Also, I wasnt sure whether or not this would be possible with ISDN PRI.

[paolo bevilacqua]

You can have multiple pri-group off a same controller, or be OK with the simple config I've suggested above.

[ShailendraK]

Hi guys,

Thanks for your replies. I am following them but still haven't reached work.

Paolo you are right buddy. It is PRI. And I can see your solution will work in my situation. I will get back soon.

I am also interested to know if it is actually possible to configure groups like Ken suggested for CAS.

Thanks again.

Shad

[Nicholas Matthews]

Hi Shad,

For partial PRIs you probably want to configure the pri-group as such. That way the router does not try to send calls out channels that aren't accepted on the other side.

controller t1 0/0/0

pri-group 1-8,10-16,23

If you're using MGCP you want to use the full 1-24 and then busy out the channels in CUCM so that ccm config doesn't overwrite it. Otherwise this is fine.

-nick

[paolo bevilacqua]

pri-group 1-8,10-16,23

That is really a strange configuration. Perhaps router will not use the excluded channels, but what if a call comes in there ?

The proper configuration is either max-calls, or multiple pri-groups encompassing all the channels.

[Nicholas Matthews]

We see this every now and then when people have two partial PRIs. Technically the other side should be configured the same so you don't have the incoming problem. This prevents having to manually busy out channels and may be a bit more graceful. Just another way to skin the cat.

-nick

[paolo bevilacqua]

I sure believe you, but there isn't anything less graceful than changing B channels on PRI, since you have to stop all calls, shutdown voice-port, remove group and then re-add port where it was referenced.

Also I think that if you ask a telco or PBX technician to setup so certain channels are skipped on a PRI, you better have tolerance to profanities.

[paolo bevilacqua]

No problem. Just don't web and drive at the same time.

[ShailendraK]

Hi All,

Thank you for the help. So as a simple solution the suggestion by Paolo is working. I have configured as follows.

The other side is sending the calls only on the first 10 channels.

On my router I have configured the follows.

interface serial 1/0:23

isdn bchan-number-order descending

This makes the 2811 send the calls from the bottom channels in descending order. Configuring the max-conn on the outgoing dial-peer is sending the calls only on the required the channels back to the network.

Thank you very much Ken, Paolo and Nick. Out of interested is there a way to configure groups of PRI and send calls through them? For example if there is a tenant situation where as a managed service provider there can be a full T1 from one provider. Is it possible to split it into different groups and send calls through them respectively?

Thank you very much

Regds

Shad

[paolo bevilacqua]

Yes, as mentioned above, multiple PRI groups groups should be supported. However, it is not of much use because in your example, telco will not know anything about multiple groups, and will place all calls on the lowest free channel anyway.

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