Information about channel negotiation E1

Unanswered Question
Apr 29th, 2009
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anyone knows if is it possible to negotiate an outbound ISDN b-channel between Cisco gateway 2851 and a PSTN switch of an Italian provider?

I have a Cisco router 2851 linked via E1 PRI (primary-net5) with PSTN and connected via MGCP with Cisco Call Manager v4.1.

From the debug message I note that the router choose the b-channel in esclusive mode and if, for any reasons, there is a problem on the line the call is busyout.

Thank for helping me


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chadlincoln Wed, 04/29/2009 - 09:06
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Can you post the configs of the router? Thanks.

cisirunite Thu, 04/30/2009 - 00:26
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Below the lines more relevant. We have also an E1 link (via E1 0/2/0) between our gateway and our alcatel 4400 PBX.

network-clock-select 1 E1 0/0/0

network-clock-select 2 E1 0/1/0

network-clock-select 3 E1 0/1/1

network-clock-select 4 E1 0/3/0

network-clock-select 5 E1 0/3/1

isdn switch-type primary-net5

controller E1 0/0/0

pri-group timeslots 1-31 service mgcp

controller E1 0/2/0

clock source internal

pri-group timeslots 1-31 service mgcp

interface Serial0/0/0:15

no ip address

encapsulation hdlc

isdn switch-type primary-net5

isdn incoming-voice voice

isdn bind-l3 ccm-manager

isdn negotiate-bchan resend-setup

no cdp enable

interface Serial0/2/0:15

no ip address

encapsulation hdlc

isdn switch-type primary-net5

isdn protocol-emulate network

isdn incoming-voice voice

isdn bind-l3 ccm-manager

no cdp enable


voice-port 0/0/0:15

cptone IT


voice-port 0/2/0:15

cptone IT


ccm-manager mgcp

no ccm-manager fax protocol cisco

ccm-manager music-on-hold

ccm-manager config server

ccm-manager config



mgcp call-agent 2427 service-type mgcp version 0.1

mgcp dtmf-relay voip codec all mode out-of-band

mgcp rtp unreachable timeout 1000 action notify

mgcp modem passthrough voip mode nse

mgcp modem passthrough voip codec g711alaw

mgcp package-capability rtp-package

no mgcp package-capability res-package

mgcp package-capability sst-package

no mgcp package-capability fxr-package

mgcp package-capability pre-package

no mgcp timer receive-rtcp

mgcp sdp simple

mgcp fax t38 inhibit

mgcp rtp payload-type g726r16 static


mgcp profile default

dial-peer voice 1 pots

service mgcpapp

port 0/0/0:15

paolo bevilacqua Thu, 04/30/2009 - 11:24
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Hi, you asked this already.

You cannot chanhe the selection using MGCP.

With H.323, you are able to.

Nicholas Matthews Thu, 04/30/2009 - 12:34
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I'm not sure if this is what you're asking, but on the MGCP page you're able to specify whether you want to do 'top-down' or 'bottom-up' on the PRI page.



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