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MGCP 3825 Troubleshooting calls not getting through

Hello Everyone,

I have a problem in a Branch office where some calls do not get through or get dropped.

Configurations is as follows:

1)2 Pri and with Overflow with N1 signalling. PRI are clean

2) Connected to a 3825. Which connected to Layer 3 switch 3750

3) Vlans for VOIP, Server network, Wifi, Users

4)CCM and Unity in Head office connected via VPN tunnel over frame relay (to T1 full 1536)

5) We use SCCP and phone are 7070,7960,7936

6) The MGCP 3825 was upgraded to the latest version 12.4(16) to solve the problem.

Question is how best to tackle the problem?

Also to fix local voice quality I just changed the codec tonight g7.11 from g7.29.

Thanks in advance or all help!



Where does the problem happen? Is it inbound and outbound calls or calls accross the VPN? (or both?)

Changing from 729 to 711 probably just masked the voice qaulity issue. 711 deals with jitter better than 729.

With an active phone call, press the information button on the phone twice. You'll see some statisics. What is the max jitter and packet loss during the call?

First thank you for your reply.

Average Jitter 5 max Jitter 58 on call across vpn

Local call via the MGCP to cell phone.

Average 2 Max 17

Inbound calls to branch office via MGCP.

Funny thing I discouvered is that if the outside calling party via the MGCP cannot reach the client in the branch. If the person in the branch office calls the remote party (that could not reach him) via MGCP he/she calls them the calls go through.

After that the remote party can call via the MGCP without any problems.


How busy are your PRI's? Is it possible your provider hasn't set the two PRI's up correctly roll over to each? What happened when the cell phone call didn't go through? Was there a message played or a fast busy?

You could try swapping the order of the two pri's so it uses the other one first. I'm wondering if inbound and outbound calls are using the same PRI first and the telco isn't rolling them over once its full.

Pri are currently utilization is about 30%

There are no slips or any problems.

sh mgcp stat

UDP pkts rx 54664, tx 54683

Unrecognized rx pkts 0, MGCP message parsing errors 0

Duplicate MGCP ack tx 0, Invalid versions count 0

CreateConn rx 4860, successful 4860, failed 0

DeleteConn rx 4848, successful 4848, failed 0

ModifyConn rx 10974, successful 10974, failed 0

DeleteConn tx 0, successful 0, failed 0

NotifyRequest rx 4025, successful 4025, failed 0

AuditConnection rx 0, successful 0, failed 0

AuditEndpoint rx 1013, successful 1013, failed 0

RestartInProgress tx 16, successful 16, failed 0

Notify tx 28929, successful 28929, failed 0

ACK tx 25720, NACK tx 0

ACK rx 28944, NACK rx 0

IP address based Call Agents statistics:

IP address, Total msg rx 54664,

successful 54664, failed 0

System resource check is DISABLED. No available statistic

DS0 Resource Statistics


Utilization: 26.08 percent

Total channels: 46

Addressable channels: 46

Inuse channels: 12

Disabled channels: 0

Free channels: 34

sh controller T1 0/0/0 brief

T1 0/0/0 is up.

Applique type is Channelized T1

Cablelength is long gain36 0db

No alarms detected.

alarm-trigger is not set

Soaking time: 3, Clearance time: 10

AIS State:Clear LOS State:Clear LOF State:Clear

Version info Firmware: 20070321, FPGA: 13, spm_count = 0

Framing is ESF, Line Code is B8ZS, Clock Source is Line.

CRC Threshold is 320. Reported from firmware is 320.

Data in current interval (649 seconds elapsed):

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)

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

I can consistantly replicate the problem by calls from a city government office...


Does the problem happen on both interfaces?

Can you go over what happens when an outside caller calls? Are they immediatly disconnected? Is there a tone or message played? Are they connected and then dropped? Do they always come in via the same interface?

Yes on both interfaces when called from an outside line. A message is played "The number is not in service please check the number or The number you have dialed is not in service"

The number via different interface?

Should turn debug isdn q931 and error messages


try debug mgcp events.

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