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SRST and AAR dont play well together

I am having a problem configuring my 2811 to support both AAR and SRST over the same PRI link. I was wondering if anyone has any advice or a solution to this problem.

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Cisco Employee

Re: SRST and AAR dont play well together

I have tried this in the lab and it works just fine. Can you give me more deatils of the problem. AAR should kick in when you exceed the BW allocated to the location for a wan call. This assumes that the WAN is up.. So, if you are in SRST mode, AAR should not function and will not. In SRST mode, you need to play with only dial peers to route calls out the PSTN

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Cisco Employee

Re: SRST and AAR dont play well together

I have tried this in the lab and it works just fine. Can you give me more deatils of the problem. AAR should kick in when you exceed the BW allocated to the location for a wan call. This assumes that the WAN is up.. So, if you are in SRST mode, AAR should not function and will not. In SRST mode, you need to play with only dial peers to route calls out the PSTN

New Member

Re: SRST and AAR dont play well together

AAR works fine, and SRST works to a fashion. The problem we were having was when the WAN was broken, routing the calls from the SRST site to the CCM site. We created the dial-peers to route the calls, but when routing the calls over the PRI link back to the CCM site, there was no q931 activity, and the phones displayed a message that the number was unknown. Note that this link was the link configured for AAR. We were able to work around this issue by using the second port on the two GW routers and sending the dial-peers over that link. I think that should not have been necessary, and I am missing something. I can include configs if requested.

Re: SRST and AAR dont play well together

Is this an MGCP gateway?

If so, have you added

call application alternate Default

to the config tell the gateway to fallback to H.323 mode in case of MGCP (WAN) failure?

If this is not an MGCP gateway or you have already added the call appl alternate Default, please post the config.

AAR is not really related to SRST. AAR kicks in when Location (CAC) settings in CCM are exceeded. This doesn't mean that the WAN is down, only that there are too many calls for the Location settings to allow.

SRST kicks in when WAN failure causes Phones to register with the gateway or connection with the MGCP call agent is lost.

Let me know if this helps by rating the post.

Michael

New Member

Re: SRST and AAR dont play well together

Michael,

Yes, it is an MGCP gateway. I have now attached the config for further assistance.

I am now ok with AAR and some of SRST. The problem that is plaguing me now is for dialing directly into the SRST area. I get re-order tones after some delay. I am dialing the same number from the CCM area that would be used by AAR.

Everything works when not in SRST.

Thanks

Jon

Re: SRST and AAR dont play well together

Hey Jon,

Since I don't see any MGCP dial-peers, I'm assuming this is not a complete config.

Regardless of where this troubleshooting takes us, you will want to add an mgcp dial-peer for the port in question. Something like:

dial-peer voice 2000 pots

application MGCPAPP

port 1/0/1:23

And to test SRST, you need to break the wan connection to the callmanager.

If I'm understanding you correctly, the issue is with calls coming into the SRST gateway from the router.

First thing that is problematic, you have no inbound call legs. The gateway will choose the default dial-peer, but DID will not be enabled there. So inbound DNIS will not be recognized.

Assuming 4 digit DNIS, add something like the following:

dial-peer voice 1000 pots

incoming called ....

direct-inward-dial

Finally, outbound PSTN calls will also fail do to lack of dial peers.

You will need to create some with destination patterns that line up with route patterns in CCM so folks can dial out in SRST mode.

Michael

New Member

Re: SRST and AAR dont play well together

Michael, First let me say thanks for helping out.

Ok, I made the changes you have suggested, and there still seems to be a problem. I have attached the latest config for you to review.

Just some background. This is a lab deployment, so we are not using full numbers. However, to use a route pattern from the CM side, the phones will dial 77..... to reach the SRST location via the simulated PRI link. The extensions are 55... on the SRST and 50... on the CM side.

Thanks again, and have a good weekend

New Member

Re: SRST and AAR dont play well together

Thanks for the help. I discovered that I was missing the command:

ccm-manager fallback mgcp

It works now, so thanks.

Cisco Employee

Re: SRST and AAR dont play well together

You do not have dial peers and that is the reason your calls are not being routed in SRST..

You need to create proper dial peers. When you want to call your central site during SRST (if your central site numbers are 59xxx), you have to send a full 10 digit DN to the telco. Otherwise, it does not know how to route it. So, your dial peer has to be:

dial-peer voice 50 pots

destination-pattern 50...

port 1/0/1:23

forward-digits all

prefix 1408555 <-- this number is the areacode and the switch code of your main site number

Apart from this you need a few more dial peers with

destination-pattern of 91[2-9]..[2-9]......

and 9[2-9]......

and 9911

etc..

Please let me know if you have any questions

Re: SRST and AAR dont play well together

The config posted also does not have the global command 'ccm-manager fallback-mgcp' which is required for the MGCP-controlled ports to fallback to H323 mode.

When in fallback/SRST mode, if you do a 'show isdn stat' the layer 3 protocol on the output should no longer be CCM-MANAGER. If it saids that then it's still in MGCP mode and not going to be usable in H323.

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