CallManager Partial T1 Support

[Aaron Harrison]

I recently attempted to configure a couple of voice gateways on a partial T1 with no success... Since then I've been looking for a solution and have found a few bits of information but I'm hoping someone can tie all these together for me or rule these out... I was configuring a 3700 series router with a T1 + DSPs, and a 6608 T1 blade. The T1 line had 6 B channels.

I've read somewhere that:

1) Prior to CM3.3, partial T1/E1 circuits with MGCP were not supported.

2) Using CM 3.3 or later you can edit a CallManager Service Parameter "B Channel Maintenance Status" to mark some channels as inaccessible by adding lines like:

S0/DS1-0@SDA123456789ABC = 0000 0011 1111 1111 1111 1111

This would block out all but the first 6 channels

3) When using the method in 2) above, you also need to check the "Enable Status Poll" item on the Gateway configuration page

4) If you are using ccm-manager config-download, the configuration of the T1 as partial on an IOS gateway (i.e. under Controller t1 1/0 the command pri-group timeslots 1-6 service mgcp) may be wiped off when you restart the gateway

Is this correct? Can anyone supply an example configuration of a partial t1 on an IOS gateway?

Also can anyone outline any specific steps that are required to configure a 6608 in this situation?

Thanks

[Aaron Harrison]

Surely someone has some idea???

Aaron

[Vance Krier]

Hi Aaron,

Right, so I think that provided info pretty much sums it up. I'd only use the 'B Channel Maintenance Status' on the 6608..as that's the only way to do it on a 6608. The key is to ensure the 'enable status poll' is checked under the port config.

FYI, I swear I've seen some issues with this in the lab. When bringing the connected device in and out of service, sometimes the 6608 gets confused and basically stops working. No q931 messages. Bounce the blade and it comes back and works correctly. Haven't done it in production other than for some basic B channel troubleshooting, so I can't speak to the production reliability aspects. Just FYI.

For IOS gateways, just configure it normally, only specifying the ports in the controller config. Something similar to as a starting point:

controller T1 1/0

framing esf

linecode b8zs

pri-group timeslots 1-6,24 service mgcp

interface Serial1/0:23

isdn switch-type primary-ni

isdn bind-l3 ccm-manager

dial-peer voice 1000 pots

application mgcpapp

port 1/0:23

I also don't trust the ccm-manager config-download command...but that is just personal preference. Its is a pretty 'neat' feature, but I've also seen it screw up and I don't / won't use it in production...again, personal preference.

Edit: Oh yea, and if you are back to backing them, don't forget to set the clocking and also set one side to 'network' for a PRI config. This is done under CM for an MGCP config or using the 'isdn protocol-emulate network' under the s1/0:23 interface for an h323 config.

Cheers,

Vance

[Aaron Harrison]

Thanks Vance...

All clear now, methinks..

Aaron