Reducing number of time slots in an E1 PRI

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Dec 9th, 2009
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Hello to everyone,

We have a gw MGCP and another H.323, CCM version 5.1.3. In order to save costs we want reduce the number of channels of our E1 PRIs (currently 30) to 10 or 20 depending of the number of calls per gateway. Our telco is preparing this request.

I think that there is not any problem to reduce the channels in pri-group time slots configuration related to incoming calls but for outgoing calls I´m not pretty sure.

There is any document with restrictions or issues related to this matter with MGCP or H323?

Thank you very much for your help.

Really appreciated.



Correct Answer by asandborgh about 7 years 5 months ago


As far as I know the following is still true:

Cisco CallManager does not support the configuration or use of a fractional PRI when you use it with MGCP. If fractional PRI is necessary, you can use H.323 instead of MGCP.




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j.rodriguez.hormigos Wed, 12/09/2009 - 07:20
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Hello Art,

This is exactly what I was looking for.:-D

Thank you very much for your quick answer. Really appreciated.

Have a good day.

Best regards.


asandborgh Wed, 12/09/2009 - 07:38
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You're very welcome.



iptuser55 Thu, 12/10/2009 - 05:24
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I thought it was supported with MGCP , the reason being we had to deploy a 8 channel E1  GW and our Cisco SE said it was ok now  and after some "chats" our SI agreed it was ok as well - remove the ccm server config commend though

asandborgh Thu, 12/10/2009 - 05:44
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I'm not the definitive answer on this, just go by what is posted.  Not a big fan of MGCP anyway, have had too many "but you gotta watch this and that", and "well it has a bug here that will cause this" over the years, especially with PRIs, both E1 and T1.  Once you set up H.323 it's good to go. Just one man's opinion.....

At any rate I would want TAC's opinion on this - if they won't pick up the phone when you have an issue because it is unsupported - now that is a problem.

Happy Trails!


Md. Mijanur Rahman Thu, 12/10/2009 - 06:39
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Yes it does , follow the procedures:

     1. at T1/E1 port configuration page at CUCM, check 'enable status poll', copy the end-point name (it might be like S0/SU0/[email protected] if at Slot0-->SubUnit0-->VWIC-1(2)MFT-T1(E1)

     2. go to the CUCM Service Parameter on 'Advance' mode and you can find there 'Clusterwide Parameter (Device - PRI and MGCP Gateway)

     3. Put a value on the described order here: S0/SU0/[email protected]=0000 0000 1111 1111 1111 1111 for T1 and S0/SU0/[email protected]=0000 0000 1111 1111 1111 1111 1111 1111 for E1

     4. Make sure the gateway is registered also the MGCP commands at gateway specially the 'pri-group timeslots 1-8, 24 service mgcp'

Please have a test and keep posted here, also don't forget to have some RnD by urself


asandborgh Thu, 12/10/2009 - 06:46
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That will work - but that was not the concern - the question was "is it supported by TAC", and per the TAC case collection item that javalenc posted it is not

Per the document:


As an alternative, busy-out the B-Channels that you are not using in Cisco CallManager by performing these steps:

Note: This procedure is not TAC-supported"



Jaime Valencia Thu, 12/10/2009 - 06:22
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The user is unable to configure fractional or partial T1 PRI with MGCP and Cisco CallManager

Currently, Cisco CallManager does not support the configuration or use of a  fractional PRI when using Media Gateway Control Protocol (MGCP) PRI backhaul.

For a workaround, use H.323 instead of MGCP if a fractional PRI is necessary.

The procedure on how to do it is in the link, but it's clearly noted this is NOT TAC supported.



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