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New Member

MGCP Fractional PRI

Is there support for fractional PRI using MGCP with any version CCM and any type IOS gateway? I know there is a service parameter that blocks out timeslots but I understand that this is not supported for production and plus it's limited to 5 per cluster.

Thanks for responses!


Re: MGCP Fractional PRI

Your understanding wrt the service parameter is correct. It is found under the Callmanager Service Advanced parameters. It will accomodate 5 of your fractional PRIs per cluster. However, fractional PRIs are not supported with any version of CCM.

Otherwise stated: Put 'em in maintenance mode, but don't call TAC if you run into issues.

Let me know if this helps by rating the post.


Change B-Channel Maintenance Status 1 : This parameter allows Cisco CallManager to change individual B-Channel maintenance status for PRI interface in real time for troubleshooting. Keep this parameter set to the default value unless otherwise instructed by a Cisco support engineer. Input Format:

Device Name = B-channel Maintenance Status


S0/DS1-0@SDA123456789ABC = 0000 1111 0000 0000 0000 0001(24 bits for T1. Channel number begins with 1 to 24 from left to right. The last one specifies the D-Channel, which does not get affected. In this example, 5th-8th B-Channels are out of service).


S1/DS1-0@DLS2-CM136-VG200-2.SELSIUSCMLAB.CISCO.COM = 0000 0000 0000 0000 0000 0000 1111 1111(32 bits for E1. B-Channel number begins with 1 to 32 from left to right. The 16th channel specifies D-Channel. The last bit does not affect any channel. In this example, 25th-31st channels are marked out of service).


The Device Name as specified in the Gateway Configuration page in Cisco CallManager Administration MUST exactly match the gateway name that this field specifies. To avoid any manual inputting mistake, copy the Device Name from Cisco CallManager Administration and paste it into this service parameter. “=” is mandatory and unique to distinguish the Device Name and BChannel Maintenance Status fields. BChannel Maintenance Status = xxxx xxxx xxxx xxxx xxxx xxxx xxxx xxxx

Where x can be

0 -- In service

1 -- Graceful out of service (Change channel status until active call ends if an active call exists on that channel.)

2 -- Forceful out of service (Tear down active call first; then, change channel status immediately if an active call exists on that channel.)

Because values other than 0, 1, or 2 are invalid, the system ignores them. Make sure that the total number of ‘x’ is either 24 for T1 or 32 for E1. Any other invalid length or mismatch (for example, 24 for E1) gets treated as error, and no action gets taken for that device.

SPACE: Optional.

The spaces between device name and '=', between ‘=’ and BCHANNEL MAINTENANCE STATUS, and between x and x, are all optional. You cannot use any space inside the DEVICE NAME field.

To use this feature, ensure that the Enable Status Poll flag on the Gateway Configuration page is checked and updated; then, the gateway must be reset for the first time. After this, changes to the service parameter will take effect without resetting the gateway.

Maximum length: 255.

New Member

Re: MGCP Fractional PRI

From my understanding, fractional PRI's are only unsupported in MGCP. You could always look at enabling your fractional PRI's using H.323, however you loose several MGCP features and the ability to manage the gateways via CallManager. I am not sure what features you are using, but this is always a option that we have used in the past when in this predicament. It would be nice to see some MGCP support.



Re: MGCP Fractional PRI

I think that setting the channel selection order to "Top Down" instead of "Bottom Up" on the gateway configuration page would have just the same effect.

New Member

Re: MGCP Fractional PRI

No, the CallManager will re-write the controller config to "timeslots 1-24" upon gateway reset.

It is possible to use MGCP now, but you cannot enter "ccm-manager config" or "ccm-manager config server X.X.X.X".

Thanks for your response!

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