PRI voice utilization

Unanswered Question
Apr 16th, 2007
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Is there a way to set a trap or to log to a syslog when my PRI is at its max or near its max with regards to channels in use?

we suspect that the PRI is getting full, but we're not sure how to log when it happens.

Any tips?

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Overall Rating: 4 (1 ratings)
MikeTomasko Mon, 04/16/2007 - 16:29
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Are they setup as MGCP or H.323? You could use CDR/CAR reports and run a Gateway Utilization Report and see when/if the PRI is being maxed out.

redrobish Mon, 05/21/2007 - 22:58
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How comes when I run a Gateway Utilization report, I only got "Gateways with zero ports"?

no data on it? do I need to do anything else?

kelvin.blair Mon, 04/16/2007 - 17:28
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You can use CDR tool for this, but the draw back is that its not real time. The other tool is to use the Real Time Monitoring Tool. This will give you an idea of the port utilization real time.

m-ketchum Mon, 04/16/2007 - 18:03
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I suppose I could, but like you said, it wouldn't be monitoring the real time status of the PRI.

I've decided to implement the following SNMP trap as a start:

snmp-server enable traps isdn chan-not-avail

Hopefully that should send a trap if the PRI runs out of channels.

Thanks for the input.

kelvin.blair Mon, 04/16/2007 - 18:08
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That will only send a trap if someone places an outbound call. At that point, you'll get no channels available message and busy. It doesn't work for inbound.

m-ketchum Mon, 04/16/2007 - 18:14
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Strange, the documentation specified inbound calls.

kelvin.blair Mon, 04/16/2007 - 18:35
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I may be wrong. The D-Channel is used for Signaling and Control of the B-Channels. If it sees that all b-channel ports are unavailable, then it is the one that reports the error. So if that is the case, then yes the trap message should work on both inbound and outbound.

Zin.Karzazi Tue, 05/22/2007 - 01:31
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I Use RTMT for that. Open RTMT->Performance->YOur CCM-> Cisco H323 (or MGCP, depends on what you are using)-> Double Click Call Active-> select Gateways you have-> you will now have a graph showing the number of all B Channels used, right click on it select-> Alert / Treshold-> Enable Alert (Severity: Warning-> Click Next: on "trigger alert when the following condition meet" select a Value ie Over 25 (which means when 25 B channels=Calls are simultanueously used you will get an email alert of it). Do this for all Gateways and all Callmanager processing Calls.

weavermj1982 Fri, 07/20/2007 - 07:50
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We have a cisco 3725 gateway adn we have just started to monitor our PRI utilisation with SNMP.

This OID will return the number of B channels in use for each serial interface in the gateway:


To get the stats for individual interfaces, add a .0, .1 etc for each interface as follows:

. = stats for first serial interface

. = stats for second serial interface

You can log these values to a text file in CSV format or graph them with something like Cricket.

In our example this gives us the utilisation of our PRI to the PSTN and a PRI that we have to our PBX

You could also use a script like this to get the values:


#Declare a date variable of the format YYYYMMDD

date=`date +"%Y-%m-%d"`

time=`date +"%T"`

pstn=`snmpwalk -c -v2c . | awk '{print $4}'`

pbx=`snmpwalk -c -v2c . | awk '{print $4}'`

if [ "$pstn" == "" ]




if [ "$pbx" == "" ]




echo $date $time,$pstn,$pbx >> stats.txt

Cron this script every minute.


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