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Silver

B-channels stay open

Hi,

I have the strange situation that an H323 gateway (2801) that is connected to a FAX server sometimes forgets to close the B-channels.

For example I execute "show voice call status" I get the message: No active calls found. But when I do a "show isdn status" I see that Layer 3 has 2 Active calls.

The result is of cource that you receive a busy tone.

Although I have not figured out what is causing this, I would like to know if there is a command that says: "if there are no active calls, clear the ISDN interface" It would saolve this problem.

Any idea?

Thanks,

JAn

7 REPLIES
Hall of Fame Super Gold

Re: B-channels stay open

Hi,

this is software defect condition called "data structure trashing". Please state exact IOS version used on the router.

Silver

Re: B-channels stay open

Hi,

My IOS version:

c2801-spservicesk9-mz.123-14.T7.bin

I tried another version with same result.

I have never heard of this "data structure trashing" Is this a bug?

thanks,

Jan

Hall of Fame Super Gold

Re: B-channels stay open

It's when the ISDN internal data structure can't correctly keep track of channel usage.

Can you upgrade to 12.4(11)XJ4 that has many many bug fixes ?

Silver

Re: B-channels stay open

Hi,

I have upgraded the 2801 to the IOS you mentioned and it seems better. I can not really say yet because I have more issues.

This is my BRI configuration (network side)

interface BRI0/2/0

no ip address

isdn switch-type basic-net3

isdn overlap-receiving

isdn protocol-emulate network

isdn layer1-emulate network

isdn incoming-voice voice

isdn skipsend-idverify

!

And debug q921 gives this:

May 31 07:16:42.127: ISDN BR0/2/0 Q921: Net RX <- IDREQ ri=25009 ai=127

*May 31 07:16:42.127: ISDN BR0/2/0 Q921: Net TX -> IDDENY ri=25009 ai=127

*May 31 07:16:42.127: ISDN BR0/2/0 Q921: Net TX -> UI sapi=63 tei=127

*May 31 07:16:42.127: ISDN BR0/2/0 Q921: Net TX -> IDCKRQ ri=0 ai=0

*May 31 07:16:44.115: ISDN BR0/2/0 Q921: Net RX <- IDREQ ri=25209 ai=127

*May 31 07:16:44.119: ISDN BR0/2/0 Q921: Net TX -> IDDENY ri=25209 ai=127

It seems to me that the ISDN card asks for a TEI from the Cisco router, and the Cisco refuses this.

Should the Cisco give a TEI to the ISDN card since it is network side?

Mind you sometimes it suddely works,

Does any one has an idea?

Thanks,

Jan

Hall of Fame Super Gold

Re: B-channels stay open

Yes it should assing a TEI. In fact when using ISDN phones, I see TEI is assigned without problems, but your trace shows otherwise.

Perhaps a TEI was assigned already ?

Does it helps if you configure "isdn tei preserve" ?

What "show isdn status" say when the problem occours? What happens if you reset both router and ISDN device ?

Silver

Re: B-channels stay open

Hi,

Normally to get layer 2 up and running I must do a clear interface BRI xx and then do a test call on the BRI (test isdn call int bri XX 123) and then layer2 gets up.

Before that I see TEI assigned.

I am already quite some time bussy with this problem and yesterday evening I changed the configuration to:

!

interface BRI0/1/0

no ip address

isdn switch-type basic-net3

isdn protocol-emulate network

isdn layer1-emulate network

isdn incoming-voice voice

isdn static-tei 0

isdn skipsend-idverify

!

The static-tei seems to work now.

I can't send you deb q921 yet, because this I have at my home PC.

I have made network side configurations in the past, and normally this doesn't give so much trouble as this configuration connecting to a FAX server with ISDN card.

Thanks for your help btw :)

Jan

New Member

Re: B-channels stay open

Hi,

I had the same problem bith BRI interface, connecting to PSTN network. It did not work until I did not enter the comand

isdn static-tei 0

I have noticed that so many users have the same problem.

regards,

alicic

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