Fractional PRI support on MGCP

Unanswered Question
dezoconnor Wed, 09/26/2007 - 23:22
User Badges:
  • Silver, 250 points or more

Workround, (c3825-spservicesk9-mz.124-12.bin)

network-clock-participate wic 0

network-clock-participate wic 1



isdn switch-type primary-net5


controller E1 0/0/0

pri-group timeslots 1-8,16 service mgcp


controller E1 0/1/0

pri-group timeslots 1-13,16 service mgcp


ccm-manager fallback-mgcp

ccm-manager redundant-host x.x.x.x

ccm-manager mgcp

ccm-manager music-on-hold

ccm-manager config server x.x.x.x

ccm-manager config (wait for router to register, then remove this command)



mgcp call-agent x.x.x.x 2427 service-type mgcp version 0.1

mgcp dtmf-relay voip codec all mode out-of-band

mgcp rtp unreachable timeout 1000 action notify

mgcp modem passthrough voip mode nse

mgcp package-capability rtp-package

no mgcp package-capability res-package

mgcp package-capability sst-package

no mgcp package-capability fxr-package

mgcp package-capability pre-package

no mgcp timer receive-rtcp

mgcp sdp simple

mgcp rtp payload-type g726r16 static

mgcp bind control source-interface GigabitEthernet0/0

mgcp bind media source-interface GigabitEthernet0/0


The above is your standard MGCP config. If you noticed that on your debug isdn q931 that your calls aren't hitting the right channels you can change the behaviour they select by selecting either top down or bottom up on the voice gateway configuration page on callmanager.

dezoconnor Thu, 09/27/2007 - 07:36
User Badges:
  • Silver, 250 points or more

Everytime you enter ccm-manager config the MGCP Gateway will download its configuration files from callmanager overwriting your fractional E1 config. Give it a try.


dezoconnor Wed, 09/26/2007 - 23:16
User Badges:
  • Silver, 250 points or more

I believe Cisco may say no but we've been using Fractional PRI's for years with MGCP. No problems reported from our customers. Infact, an install I did last week was 2 Fractional E1's (one e1 had 13 and the other had 8 channels) into one MGCP gateway.


i have a question about this workaround.

I have a scenario with a Cat 6000 E1 Blade and need a separate QSIG Gateway with a fractional E1 with 10 B-Channels. I remember that i can disable some B-Channels in the CCM Service Parameters, but i think this will also affect the E1 Blades, right ?

If i do not disable this channels and work with the config you provided, how does the ccm know, that he cant use the 11th channel ?

Kind regards


Rob Huffman Fri, 11/09/2007 - 06:38
User Badges:
  • Super Blue, 32500 points or more
  • Hall of Fame,

    Founding Member

  • Cisco Designated VIP,

    2017 IP Telephony, Unified Communications

Hi Steffen,

The pertinant commands here as far as I know are;

controller E1 0/0/0

pri-group timeslots 1-8,16 service mgcp

controller E1 0/1/0

pri-group timeslots 1-13,16 service mgcp

I don't think any disabling of B-Channels on CCM itself is necessary.

Hope this helps!


AJAZ NAWAZ Fri, 11/09/2007 - 07:04
User Badges:
  • Silver, 250 points or more
allan.thomas Fri, 11/09/2007 - 08:49
User Badges:
  • Blue, 1500 points or more

The limitation within CCM is that you can only configure the channel maintenance status for 5 gateways. This cerntainly is the case in CCM5.x

Therefore I would not specifically reconfigure the pri-group unless it was absolutely necessary. If you are able to change the maintenance status, then I would recommend this.

However, as I have mentioned on previous posts, I would only configure the pri-group with the respective number of time-slots only in order to preserve DSPs for transcoding/conference resources on the same gateway.




This Discussion