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B-channels stay open

j.huizinga
Level 6
Level 6

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 7

paolo bevilacqua
Hall of Fame
Hall of Fame

Hi,

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

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

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 ?

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

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 ?

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

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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