Cisco - PBX problem - LOS detected

Unanswered Question
Aug 26th, 2009

Hi guys,

I have two routers, a 3745 with c3745-ipvoicek9-mz.124-18.bin and a 2811 with c2800nm-spservicesk9-mz.124-3i.bin connected to a PBX Mitel.

Both my routers connect to the Pbx via on E1.

The configs are

3745:

sh run | s controll

controller E1 1/0

pri-group timeslots 1-31 service mgcp

controller E1 1/1

shutdown

sh run | s Serial

interface Serial1/0:15

no ip address

encapsulation hdlc

isdn switch-type primary-qsig

isdn timer T310 120000

isdn overlap-receiving

isdn protocol-emulate network

isdn incoming-voice voice

isdn bind-l3 ccm-manager

no cdp enable

2811

sh run | s controll

controller E1 0/0/0

pri-group timeslots 1-31 service mgcp

sh run | s Serial

interface Serial0/0/0:15

no ip address

isdn switch-type primary-qsig

isdn protocol-emulate network

isdn incoming-voice voice

isdn T310 120000

isdn bind-l3 ccm-manager

no cdp enable

The problem is that from time to time (about 20 times a month) the E1 connection is dropped and then restarted in a couple of minutes.

This is a log form the routers

006980: Aug 26 11:37:52.711: %CONTROLLER-5-UPDOWN: Controller E1 0/0/0, changed state to down (LOS detected)

006981: Aug 26 11:37:52.739: %ISDN-6-LAYER2DOWN: Layer 2 for Interface Se0/0/0:15, TEI 0 changed to down

006982: Aug 26 11:37:54.712: %LINK-3-UPDOWN: Interface Serial0/0/0:15, changed state to down

006983: Aug 26 11:38:38.712: %CONTROLLER-5-UPDOWN: Controller E1 0/0/0, changed state to up

006984: Aug 26 11:38:40.712: %LINK-3-UPDOWN: Interface Serial0/0/0:15, changed state to up

006985: Aug 26 11:39:29.305: %ISDN-6-LAYER2UP: Layer 2 for Interface Se0/0/0:15, TEI 0 changed to up

I can see the reason is LOS detected but i don't really know what that is.

Can anyone help me please?

Thank you,

Good day.

I have this problem too.
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Paolo Bevilacqua Wed, 08/26/2009 - 00:58

you should use "clock source internal" for this connection.

Also check you're using proper 120 Ohm cable with the right pairing.

ronin2k8cronus Fri, 08/28/2009 - 01:24

Indeed my conf on CUCM 7 is clock source external. My question is why do you think changing the clock source will solve the problem?

Thank you very much for your help.

Paolo Bevilacqua Fri, 08/28/2009 - 01:42

Clock source must be internal, because from your configuraation appears that PBX is left as "user side".

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