Moving ATT (legacy Pac Bell) PRI's to Cisco Gateway MGCP

[jgbmt]

Hello,

We are migrating two ATT (Legacy Pac Bell) PRI's that are currently connected to an Option 81 PBX over to a Cisco ISR 2921 voice gateway using MGCP. The layer 2 and layer 3 come up when they connect to the Cisco gateway card, and Multiple Frames Established is shown in the CLI, but no calls can be processed. When a debug q.931 is ran, there are messages that come up stating that individual channels are trying to reset or something to that effect. I don't have the syntax since we had to reconnect to the PBX. Any ideas what may be wrong?

I posted here in Nortel in case someone may have insight into this type of scenario..

Thanks!

 

[KCFLHRC]

My guess is you have a protocol mismatch. I would print out how they were provisioned in the Nortel and make sure they are provisioned the same way in the Cisco.

LD 22
PRT
CEQU

and also print out the ADAN for the D-channels

 

[jgbmt]

Thanks for the reply!

I have the Cisco as ISDN NI-2 which the ADAN lists for both. It prints out that these are set to Clock EXT and User side. I don't know how to see what setting tells me how many digits are being sent to us, though. How can i find this out?

Looks like Loop 34 and 50 are the PRI's both with D Channels Primary is 34 / 50 is Backup.

I tried moving the Backup PRI to the Cisco and the errors seem to clear up, but i couldnt recevie calls because they are obviously coming in on the Primary. I will attempt to make calls out the Backup and see if this is good.

 

[jgbmt]

... I am assuming that IFC NI-2 means that it is ISND Protocol NI-2 - (just making sure) ... and do you anticipate any impact if i move the Back up to Cisco?

 

[jgbmt]

I found a CSR that has the following:

USOC PRAS3 - PRI Interface 23 B + 1 Backup D (M-M) - D Channel Sharing

There is no mention to NFAS and I remember previously working with a Tester and him explaining that these PRI's were not in NFAS. Each of the PRI's show to have their own DCH.

Thank you,

 

[KCFLHRC]

Yep, sounds like NI2, National ISDN 2, and if there is a primary and back up d-channel then definitely NFAS would be yes. NFAS meaning more than 1 PRI shares the same d-channel, correct? Otherwise there would just be 2 stand alone d-channels one for each PRI. Not a primary and backup. Also look for B8ZS/ESF in the CEQU

 

[KCFLHRC]

If you move the backup to the Cisco the CO will still see the primary as active and never switch to the backup

 

[KCFLHRC]

Does this help??

https://www.cisco.com/c/en/us/suppo...ISDN service that,24 channels are B channels.

 

[jgbmt]

Thanks KCFLHRC!

This doc is very helpful. The only question is now if Cisco will support this NFAS PRI group in an MGCP gateway as this is what we have.

The doc mentions: "int_number - A value assigned by the service provider and used to uniquely identify the PRI. The values possible range from 0 to the highest t1" --> How can I find this info in the Option 81 configuration (LD and line)?

All your help is appreciated!

 

[jgbmt]

I found a Cisco article that states Cisco MGCP does not support NFAS. I need to configure the gateway as H323.... have you any guides or scripts on how to do this? (configure a Cisco ISR 2921 as H323 voice gateway?

 

[KCFLHRC]

Not a Cisco guy at all. I'm guessing though since the Cisco will not support NFAS then you will need to get the Provider to make a change on the PRI's so they each have their own D-channel instead of NFAS. But that will require down time on the circuits and a change in the Nortel also. I would just coordinate your cutover to the Cisco with the Telco reprovisioning the PRI's.

That INT number will more than likely be in the D-channel config on the Nortel. Print out the D-channel ADAN

 

[jgbmt]

Got it... I think I found some Cisco H323 stuff.

In ADAN, is see:


IFC NI2
ISDN_MCNT 300

Can you provide some insight into these valuse?

 

[KCFLHRC]

IFC NI2 is just telling you that is the protocol on the PRI

ISDN_MCNT 60-(300)-350 Layer 3 call control message count per 5 second time
interval.