E1 PRI Channel allocation

Unanswered Question
Feb 4th, 2009

is it possible to dedicate the E1 PRI channels ....for eg: if management team required to dedicate E1 PRI first 10 channels.Others can share 11 to 30 channels....or 15 channels dedicated for incoming calls and next 15 channel dedicating for outgoing calls.

Is there any solution for configuring the above E1 fragmentation using MGCP/H323 gateway....

I have this problem too.
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gogasca Wed, 02/04/2009 - 22:22

Sure you can - have a read of the note below.

cheers Gonzalo

The customer had two different users on his VOIP network and he wanted to

split a single E1 PRI service between these users so that one user would use certain B channels and the

other user would use different one for outwards calls on the CME router.

The phone company was able to assign these B channel groups with different

number ranges for inwards calls.

There is a new feature in 12.4 code that allows you to define individual

timeslots of the PRI and assign them to different trunk groups. These trunk groups can be used instead of a

voice port in a POTS dial peer, so you can direct calls to very specific B

channels on the PRI. Following is a config that demonstrates this feature -


controller E1 1/0

pri-group timeslots 1-31

trunk-group Customer1 timeslots 1-10

trunk-group Customer2 timeslots 11-20

trunk-group Customer3 timeslots 21-30



dial-peer voice 1 pots

description - enable DID on group 1

incoming called-number .


trunkgroup Customer1


dial-peer voice 2 pots

description - enable DID on group 2

incoming called-number .


trunkgroup Customer2


dial-peer voice 3 pots

description - enable DID on group 3

incoming called-number .


trunkgroup Customer3



dial-peer voice 5500 pots

trunkgroup Customer1

description - Customer 1 : access code 771

destination-pattern 771


dial-peer voice 5501 pots

trunkgroup Customer2

description - Customer 2 : access code 772

destination-pattern 772


dial-peer voice 5502 pots

trunkgroup Customer3

description - Customer 3 : access code 773

destination-pattern 773


dial-peer voice 1001 voip


session target ipv4:


dial-peer voice 1002 voip


session target ipv4:


dial-peer voice 1003 voip


session target ipv4:


In this case, Customer1 users would dial 771 as an access code, Customer2

would dial 772

and Customer3 would dial 773. These access codes would 'steer' the call to

the appropriate

timeslots on the PRI.

This could also be enhanced using Class Of Restrictions (COR) to prevent

each group from

potentially calling out the other user's channels.


It won't work with MGCP - the channel selection is controlled from the

CallManager, so the trunk group commands will not be active under MGCP


For the incoming calls, it wont work, you can play with b-channel selection, or aditional circuits :)

febinattingal Fri, 02/27/2009 - 01:10

Thanks for your excellent support....

Is there any possibility to allocate incoming calls in ascending order.

Our issue is we have not enough dsp resource to configure 31 e1 channels.only 24 channels dsp only available.sometimes incoming call hitting to 25 - 31 channel.that times it will revert unallocated channel error and disconnect the call automatically.

Is there any solution for configuring to allocate first 24 channels for incoming calls...?

Thanks in Advance

Paolo Bevilacqua Fri, 02/27/2009 - 04:16

No, you cannot have any control for incoming calls, consequently either buy the DSP module for 30 channels, or configure the device on the other side to use less channels.

febinattingal Fri, 02/27/2009 - 05:07

Can you please explain how to configure the device on the other side to use less channels ?

It seems like if any incoming call coming ,it randomly allocate channels,sometimes allocate after 24 - 31 ,that time only we facing this issues.

Paolo Bevilacqua Fri, 02/27/2009 - 05:46

It depends by the type of device, basically you have to configure it for a number of channels less that 30.

Nicholas Matthews Fri, 02/27/2009 - 05:22

I think this is the command you're looking for:

interface Serial 0/0:23

isdn bchan-number-order ascending



febinattingal Fri, 02/27/2009 - 10:53

Thanks for your valuable reply...

isdn bchan-number-order ascending only applicable for outgoing calls.

My problem is i have one E1 PRI 31 channel terminated in my MGCP gateway. But due to the lack of DSP resourse ,only able to configure 24 channels. from 25 - 31 channels not available in my gateway.

Whenever incoming calls coming,it randomly choosing the bchannels. some times it choosing channels from 25 -31 ,that time call disconnecting with debug message "Unallocated channel".

Is there any possibilty to set incoming calls also in ascending order?

Also is there any solution for dedicating first 10 channel for incoming and rest of them for outgoing using MGCP gateway...

Thanks in advance

Paolo Bevilacqua Fri, 02/27/2009 - 11:14

You have exposed this problem already, and have been told that the router cannot control in any way the INCOMING channel chosen by the connected device, that is logical if you think about, now what is not clear to you ?

acharyr123 Tue, 06/01/2010 - 22:24


I have a video conferencing unit that required 8 channels. Using your method can i dedicate 8 channels to the VC unit & use rest others for incoming/outgoing calls?

I am using CCM 7.1.3 with VG: 12.4

Kindly suggest.


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