Issue with MGCP Gateway and T1 access

[Autresrhumbs]

Hello Everyone,

i am setting up a Cisco 2921 gateway with a T1 card, managed with MGCP.

When I do sh ccm-manager, the gateway is registered with its main CUCM and the backup is ready. Nothing unusual here.

I have then configured the T1 card with protocol 4ess. When I connect the T1 access from Verizon (which was previously connected to a Centrex pbx) , I see the multiple_frame_established with sh isdn status.

What is wrong is that I just simply cannot receive call from there (I haven't tried to place calls yet).

With a debug isdn q931 and q921, nothing happens  when I call a number in the DID range...

When I plug it back to the Nortel pbx, it works fine.

Should we at least see something with these 2 debug commands even though something is wrong with the layer 3?

(I do see the Rx-Tx keep alive from time to time, but nothing else)

Is it more something related to my gateway configure or with the Telco ?

Thanks a lot for your help.

PS: what is also weird is that the port is showing unregistered sometimes on the CUCM. And it regularly switches from main to backup CUCM (I saw this with the sh ccm-manager)

[Suresh Subramanian]

If you see the multiple_frame_established with sh isdn status and if you place the call out, do you get the output with debug isdn q931 turned on?

with the above isdn status, if you don't get any output with debug isdn q931 for inbound calls, may be your provider is not sending the call on this PRI. You can also have a word with them.

Also with debug isdn q921 turned on, you should receive SABME message from provider and the router should ack it with UA.

you can follow the below link to troubleshoot the PRI issues

http://www.cisco.com/c/en/us/support/docs/wan/t1-e1-t3-e3/8131-T1-pri.html

[Autresrhumbs]

Thanks Suresh, will check that.

Just one question: if the card is unregistered in the CUCM and a call arrives on the GW, will we see something with the q931 and q921 debug commands?

[Suresh Subramanian]

When the PRI is unregistered, the layer2 status will be TEI Unassigned and hence Telco will not deliver any calls on that PRI card until it turns up with Multiframe Established.

so you will get output for debug isdn q921 but not for 931

[Autresrhumbs]

Ok... It is a nfas configuration...

Is it compatible with CUCM? 

[Suresh Subramanian]

nfas is not supported with mgcp

[Autresrhumbs]

Ok thanks for your feedback.

So if I want to make it work with MGCP, I need to ask the provider to change it to standard PRI with dedicated D channel?

No way to make it work without that?

Thanks.

[Suresh Subramanian]

If you want to keep MGCP GW, then you should ask the telco to change the configuration from NFAS to Standard PRI.

If you want to configure NFAS, then change the GW to either H323 or SIP.

[Autresrhumbs]

OK, thanks for your help Suresh.

I have contacted Verizon and they told me they have made the change.

So we now have 2 separated T1.

But still nothing coming UP on the Cisco GW.

I have opened a TAC and talked to an engineer from Cisco. He told me this is probably a bug on the version of my GW (15.2(4)M)...

I am now waiting for his feedback. I'll let you know!

[Suresh Subramanian]

Can you share the show isdn status and debug isdn q921 please? 

[Autresrhumbs]

Sure, please find it attached.

Thanks.

[Suresh Subramanian]

Try removing the "isdn bind-l3 ccm-manager" command from serial interface and add it  back.

​Also no mgcp and mgcp once.

​Also ensure you have correct switch type, encapsulation and crc configured as instructed by telco.

Please collect debug isdn q921 again and show ccm-manager also

[Autresrhumbs]

Did that, but nothing better...

[Autresrhumbs]

Oups, sorry.

Did not see your last post.

I added the commands:

mgcp bind control source-interface Port-channel1
mgcp bind media source-interface Port-channel1

Since I have a port channel and... I now have:

MULTIPLE_FRAME_ENABLED on both T1s, which seems good.

BUT ! When i make an outgoing call, nothing happens. And when I have a look at the CUCM, both interfaces are still unregistered.

If i make an incoming call, I get the following:

*Dec  6 18:40:15.151: ISDN Se0/0/0:23 Q931: SETUP pd = 8  callref = 0x03DC
        Bearer Capability i = 0x8090A2
                Standard = CCITT
                Transfer Capability = Speech
                Transfer Mode = Circuit
                Transfer Rate = 64 kbit/s
        Channel ID i = 0xA98384
                Exclusive, Channel 4
        Facility i = 0x9F8B0100A1080201010201008400
                Protocol Profile =  Networking Extensions
                0xA1080201010201008400
                Component = Invoke component
                        Invoke Id = 1
                        Operation = CallingName
                                Name not available
        Calling Party Number i = 0x1183, '33661327526'
                Plan:ISDN, Type:International
        Called Party Number i = 0x80, '8601'
                Plan:Unknown, Type:Unknown

But my phones are not ringing, despite the fact that I have made a translation pattern 86XX associated with the correct CSS and partition...

So I don't clearly understand what's going on...

[Suresh Subramanian]

have you selected the right CSS in the Gateway Endpoints under inbound call settings?

make sure the CSS you selected has the partition of that translation pattern.

can you share the complete debug isdn q931 for the inbound call?

Please share the show ccm-manager & show mgcp endpoint from the gateway.

if the endpoints show registered in IOS and not in CUCM, you may restart the Cisco RIS Data collector service