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Troubleshooting Voice Gateways

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This is for Cisco Voice Gateways aka Cisco routers acting as configure to run as a Voice Gateway. Does not include VG's aka PSTN Voice Gateways.

Quick Troubleshooting commands;

1. Show version - View the uptime of the router. Verify if your ticket was generated because the Voice Gateway rebooted.

2. Show log - View last logged activity. Pay attention to what you see in the logs.

This entry means the Voice T1 or PRI physically flapped - Caused by clocking errors on the T1 or a temporary L1 disconnection.

Case 1
%CONTROLLER-5-UPDOWN: Controller T1 0/1/0, changed state to up
%ISDN-6-LAYER2UP: Layer 2 for Interface Se0/1/0:23, TEI 0 changed to up
%LINK-3-UPDOWN: Interface Serial0/1/0:23, changed state to up
%MARS_NETCLK-3-CLK_TRANS: Network clock source transitioned from priority 10 to priority 1 

This entry means that the IP Phones at the site unregistered with the Call Manager connection via the WAN (VoIP), and registered with the Voice Gateway locally - Caused when the WAN device flaps. When the WAN came back up, the phones re-registered with the Call Manager via the WAN (VoIP). Or when SRST kicks in.

Case 2
%IPPHONE-6-REGISTER_NEW: ephone-2:SEP<MAC>  IP:X.X.X.X Socket:2 DeviceType:Phone has registered.
%IPPHONE-6-UNREGISTER_NORMAL: ephone-2:SEP<MAC> IP:X.X.X.X Socket:2 DeviceType:Phone has unregistered normally.
%IPPHONE-6-UNREGISTER_NORMAL: ephone-1:SEP<MAC> IP:X.X.X.X Socket:1 DeviceType:Phone has unregistered normally.

This entry means the PSTN or Voice Anaglog ports (FXS/FXO) ports flapped - Caused by a L1 flap of the analog lines.

Case 3
%LINK-3-UPDOWN: Interface Foreign Exchange Office 0/3/0, changed state to up
%LINK-3-UPDOWN: Interface Foreign Exchange Office 0/3/1, changed state to up
%LINK-3-UPDOWN: Interface Foreign Exchange Office 0/3/2, changed state to up
%LINK-3-UPDOWN: Interface Foreign Exchange Office 0/3/3, changed state to up

If Case 1, the issue the following command; Show Controllers T1 (this will list a detailed output of all T1 controllers on the Gateway)

Show controllers t1
T1 0/1/0 is up.     The controller is administratively UP
Cablelength is long gain36 0db   Length of the T1 cable
AIS State:Clear  LOS State:Clear  LOF State:Clear    Alarm info seen here, if any
Framing is ESF, Line Code is B8ZS, Clock Source is Line.   Line coding,framing and  clocking info.
CRC Threshold is 320. Reported from firmware  is 320.
Data in current interval (236 seconds elapsed): Current error information, check here
to verify if errors are currently incrementing or not.
0 Line Code Violations, 0 Path Code Violations
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs
Total Data (last 24 hours)                 Old error information (past 24hrs)
0 Line Code Violations, 0 Path Code Violations,
0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins,
0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 0 Unavail Secs

If the controller is UP, then run the command listed below. 

3. Show isdn status This command will tell you the status of the ISDN interface (which is our T1) on layers 1,2 and 3.

ISDN Serial0/0/0:23 interface   ---> T1 controller #
   Layer 1 Status ---> Should be ACTIVE, anything else and you have a L1 issue
   Layer 2 Status State ---> Should be MULTIPLE_FRAME_ESTABLISHED. 

If you see anything else (such as TEI_ASSIGNED), then it's a L2 issue. Run the command  
many times to see if maybe L2 is bouncing between FRAME ESTABLISHED and ASSIGNED.

If Case 2, then please check the associated WAN device for WAN flaps and/or route refreshes.

If Case 3, the run the command below, to check the status of the analog voice <FXO/FXS) ports. Note that the analog ports will not show in the Show interface description command.

4. Show voice port summary

0/3/0          --  fxo-ls      up    dorm idle     on-hook  y ---> Phone is 'On-Hook'
0/3/1          --  fxo-ls      up    dorm idle     on-hook  y ---> Phone is 'On-Hook'
0/3/2          --  fxo-ls      up    dorm idle     on-hook  y ---> Phone is 'On-Hook'
0/3/3          --  fxo-ls      up    dorm idle     on-hook  y ---> Phone is 'On-Hook'

Note that there are no incoming calls on those FXO/FXS ports because the phone is 'On-Hook'. Make a test call using a number configured for the FXS/FXO ports, if the port is working correctly, you should see the 'STATUS' change to 'Ring-Detect', and then 'Off-Hook'. Also run the command listed below when checking to see if the call is reaching the gateway;

5. Show voice call status

Sh voice call status 
CallID     CID  ccVdb      Port             DSP/Ch  Called #   Codec    Dial-peers
0x76C3     D44  0x463121AC 0/1/0:23.14      0/1:1  *           g711ulaw  0/0
1 active call found 

Note that there's '1' active call, on T1 port 0/1/0:23, channel 14. You know it's a T1 port because of the :23. This is because of the 24 T1 voice channels that are on a voice T1.

If you don't see the :23, it means that the call is probably coming in on the FXS/FXO port. If you don't see the call at all, then the call is not reaching the gateway and the PSTN may been to be engaged or the dial-peers of the 'calling' gateway need to be checked.

This article uses material from the Wikipedia article Troubleshooting Voice Gateways, that was deleted or is being discussed for deletion, which is released under the Creative Commons Attribution-ShareAlike 3.0 Unported License.
Author(s): IShadowed Search for "Troubleshooting Voice Gateways" on Google
View Wikipedia's deletion log of "Troubleshooting Voice Gateways"

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