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one way & no way audio

Have CM 4.2 Cluster with IPCC co-res on pub.

2801 MGCP GW with fractional PRI (10 channels). Have service params set in callmanager>advanced settings to support the frac pri.

IOS is 12.4(9)T.

CM Clusster is distributed between 2 locations. All devices on pub have Device Pool configured the same (i.e. CTI ports, CTI RP's, Phones, GW) with MRGL's, Locations, etc.

Calls from PSTN intermittantly have one way/no way audio.

GW has mgcp bid statements for control and media.

Did PCM capture and don't see any audio coming from PSTN side on calls with one way / no way audio.

Don't even get ringback (progress indicator) when calls get the audio prob.

So far only experience this on inbound calls randomly.

I've checked each DS0 as calls were delivered to least busy channel inbound so there is no consistency there.

Would the general consensus be thatt this is a telco prob or could possibly be a prob on my side?

Have case open on this but need more help if anyone has any suggestions.

I've gone thru the troubleshooting audio probs.

Only thing i've not yet done is to remote all access lists and qos. Having said that if this were the prob would'nt this be a consistent issue?




Re: one way & no way audio


I see that you have the bind statements. Do you have any loopbacks or any other interfaces on the router with another ip address ? I have had this same problem, even with the bind statements for MGCP media and control in the router. THis is a bug and doesnt seem to have fixed in IOS version 12.4.9T or T1. Can you paste a "sh mgcp" and confirm that "MGCP bind media is inactive". If thats the case, you are hitting that bug. The workaround is to manually key in the MGCP bind statement for media. I will try to get you the bug ID if i can find it.



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Re: one way & no way audio

This bug ID is similar to the situation that i was talking about.


New Member

Re: one way & no way audio

Thanks for input - have a loopback and have pasted sh mgcp;

What's the scoop with the loopback?

If this is caused by doing "no mgcp" "mgcp" do you need to do a reaload to fix or just manually re-enter the mgcp bind statements?

sh mgcp

MGCP Admin State ACTIVE, Oper State ACTIVE - Cause Code NONE

MGCP call-agent: 2427 Initial protocol service is MGCP 0.1

MGCP validate call-agent source-ipaddr DISABLED

MGCP validate domain name DISABLED

MGCP block-newcalls DISABLED

MGCP send SGCP RSIP: forced/restart/graceful/disconnected DISABLED

MGCP quarantine mode discard/step

MGCP quarantine of persistent events is ENABLED

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

MGCP dtmf-relay for voAAL2 is SDP controlled

MGCP voip modem passthrough mode: NSE, codec: g711ulaw, redundancy: DISABLED,

MGCP voaal2 modem passthrough disabled

MGCP voip modem relay: Disabled

MGCP T.38 Named Signalling Event (NSE) response timer: 200

MGCP Network (IP/AAL2) Continuity Test timer: 200

MGCP 'RTP stream loss' timer disabled

MGCP request timeout 500

MGCP maximum exponential request timeout 4000

MGCP rtp unreachable timeout 1000 action notify

MGCP gateway port: 2427, MGCP maximum waiting delay 3000

MGCP restart delay 0, MGCP vad DISABLED


MGCP system resource check DISABLED

MGCP xpc-codec: DISABLED, MGCP persistent hookflash: DISABLED

MGCP persistent offhook: ENABLED, MGCP persistent onhook: DISABLED

MGCP piggyback msg ENABLED, MGCP endpoint offset DISABLED

MGCP simple-sdp ENABLED

MGCP undotted-notation DISABLED

MGCP codec type g711ulaw, MGCP packetization period 20

MGCP JB threshold lwm 30, MGCP JB threshold hwm 150

MGCP LAT threshold lwm 150, MGCP LAT threshold hwm 300

MGCP PL threshold lwm 1000, MGCP PL threshold hwm 10000

MGCP CL threshold lwm 1000, MGCP CL threshold hwm 10000

MGCP playout mode is adaptive 60, 40, 200 in msec

MGCP Fax Playout Buffer is 300 in msec

MGCP media (RTP) dscp: ef, MGCP signaling dscp: af31

MGCP default package: line-package

MGCP supported packages: gm-package dtmf-package trunk-package line-package

hs-package rtp-package ms-package dt-package mt-package

sst-package pre-package md-package

MGCP Digit Map matching order: shortest match

SGCP Digit Map matching order: always left-to-right

MGCP VoAAL2 ignore-lco-codec DISABLED

MGCP T.38 Max Fax Rate is DEFAULT



MGCP T.38 Fax NSF Override is DISABLED

MGCP T.38 Fax Low Speed Redundancy: 0

MGCP T.38 Fax High Speed Redundancy: 0

MGCP Fax relay SG3-to-G3: ENABLED

MGCP control bound to interface FastEthernet0/1.180

MGCP media bound to interface FastEthernet0/1.180

MGCP Upspeed payload type for G711ulaw: 0, G711alaw: 8

MGCP Static payload type for G.726-16K codec

MGCP Dynamic payload type for G.726-24K codec

MGCP Dynamic payload type for G.Clear codec

MGCP Dynamic payload type for NSE is 100

MGCP Dynamic payload type for NTE is 99

MGCP rsip-range is enabled for TGCP only.

MGCP Guaranteed scheduler time is disabled

MGCP DNS stale threshold is 30 seconds

Re: one way & no way audio


Your configs look fine and your sh mgcp do show

MGCP control bound to interface FastEthernet0/1.180

MGCP media bound to interface FastEthernet0/1.180

In my case, I had to remove the loopback interface from the system and just use the fastE interface in the bind statements. That seem to have fixed the problem for me. But later due to another bug in SRST we had to upgrade from 12.4.9T to 12.4.9T1 and the bug seems to have come back. Our media bind status showed inactive in sh mgcp. We have had to manually key in the media bind statement for mgcp, when we have this problem. I am not sure how to proceed from here as Cisco may not have a resolution for this yet.

Is the loopback ip address routable in your network. In my case, my loopback address was not routable and since MGCP was registering with the loopback address with callmanager, the one way audio problem was occuring. If your loopback is routable, try using that in the mgcp bind commands instead of the fastE interface.



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New Member

Re: one way & no way audio

Thanks for tips.

The loopback is routable as it is used for cue and i can leave vm messages from anywhere on our network so definitly routable.

When troubleshooting your problem when you first had it - did you do any pcm captures?

Did they show no audio coming from pstn? Also, i get one way and no way audio. Did you have same?

Curious to know if you are hitting same thing as me.

When i'm home i cannot seem to reproduce the problem. Only can reproduce at work. Kind of frustrating as it does not happen very often - just often enough to spook people.

So based on what you are saying if loopback is routable use that for binding media and control and we should be good?



Re: one way & no way audio


i only had oneway audio issue, where the pstn cannot hear us, but audio from the pstn caller could be heard by ip phone user. (Because the mgcp gateway had registered with a non routable loopback and callmanager nor ip phone could reach that loopback).

Have you checked your T1 to see if there are any errors ? Did you have the telco test the circuit ?

New Member

Re: one way & no way audio

have called telco to test but no response yet.

No errors on the T1 controller.

do you figure that your issue was a simple routing issue or was there something in addition to that due to the loopback.

do you think mgcp just wants to bind to the loopback for some reason no matter what you specify in the mgcp bind (i.e. a bug).

Just wondering if it is worth it for me to bind to this loopback or not. Don't think it will hurt tho.

What was really strange was that on the call that we did the pcm capture on the ip phone user could hear me but i cound not hear him.

The cisco engineer said that he could not see any audio in the pcm capture coming from the pstn - very weird...not sure about that tho.

Anyway, don't know what to think about the loopback and the mgcp bind.

You think there is a bug there?



Re: one way & no way audio


Give it a shot, by binding with the loopback. I did see a few similar bugs , the workaround was to use loopback.


New Member

Re: one way & no way audio

Just wanted you to know that the problem still exists and I've been able to reproduce on outbound but have not yet been able to catch one in progress and keep itup to capture necessary info.


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