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Community Member

ISDN BRI switch-type configuration

Hi all, does anybody can explain to me why the following command is replaced AFTER RELOADING my 2801 gateway:

int bri X/X/X

isdn switch-type vn3

replaced by

int bri X/X/X

isdn switch-type basic-net3

I have to keep vn3 signaling.

IOS is 12.4(15)T1.

Thanks a lot.

Julien.

9 REPLIES
Silver

Re: ISDN BRI switch-type configuration

Do you have the ISDN switch-type configured globally too?

check this out:

<http://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/113t/113t_3/natisdn.htm#27502>

I would remove the interface level command and try to add the global command only first.

Ajaz

Community Member

Re: ISDN BRI switch-type configuration

Hello Ajaz

sure i have the same command ! I try to remove it from interfaces and globally. Then configure switch-type globally => switch-type vn3 automatically configured on all bri interfaces. Reload again and switch-type changed to basci-net3 on all bri !

Julien.

Silver

Re: ISDN BRI switch-type configuration

Please post the output from show ISDN status and debug ISDN q931

Ajaz

Community Member

Re: ISDN BRI switch-type configuration

Here is show isdn status after removing isdn switch-type vn3 from all bri interfaces, then reconfiguring vn3 in global mode:

NB44001R#sh isdn status

Global ISDN Switchtype = vn3

%Q.931 is backhauled to CCM MANAGER 0x0003 on DSL 0. Layer 3 output may not apply

ISDN BRI0/0/0 interface

dsl 0, interface ISDN Switchtype = vn3

L2 Protocol = Q.921 0x0000 L3 Protocol(s) = CCM MANAGER 0x0003

Layer 1 Status:

ACTIVE

Layer 2 Status:

TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED

Layer 3 Status:

0 Active Layer 3 Call(s)

Active dsl 0 CCBs = 0

The Free Channel Mask: 0x80000003

%Q.931 is backhauled to CCM MANAGER 0x0003 on DSL 1. Layer 3 output may not apply

ISDN BRI0/0/1 interface

dsl 1, interface ISDN Switchtype = vn3

L2 Protocol = Q.921 0x0000 L3 Protocol(s) = CCM MANAGER 0x0003

Layer 1 Status:

ACTIVE

Layer 2 Status:

TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED

Layer 3 Status:

0 Active Layer 3 Call(s)

Active dsl 1 CCBs = 0

The Free Channel Mask: 0x80000003

%Q.931 is backhauled to CCM MANAGER 0x0003 on DSL 2. Layer 3 output may not apply

ISDN BRI0/1/0 interface

dsl 2, interface ISDN Switchtype = vn3

L2 Protocol = Q.921 0x0000 L3 Protocol(s) = CCM MANAGER 0x0003

Layer 1 Status:

ACTIVE

Layer 2 Status:

TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED

Layer 3 Status:

0 Active Layer 3 Call(s)

Active dsl 2 CCBs = 0

The Free Channel Mask: 0x80000003

%Q.931 is backhauled to CCM MANAGER 0x0003 on DSL 3. Layer 3 output may not apply

ISDN BRI0/1/1 interface

dsl 3, interface ISDN Switchtype = vn3

L2 Protocol = Q.921 0x0000 L3 Protocol(s) = CCM MANAGER 0x0003

Layer 1 Status:

DEACTIVATED

Layer 2 Status:

Layer 2 NOT Activated

Layer 3 Status:

0 Active Layer 3 Call(s)

Active dsl 3 CCBs = 0

The Free Channel Mask: 0x80000003

Total Allocated ISDN CCBs = 0

and here is a deb isdn q931.

Communications are OK but i have problems when switching from mgcp backhaul to SRST and switchover from SRST to mgcp backhaul. Layer 1 stay in a deactivated state and i think it could be related to this switch-type configuration.

Call is not answered in this example.

NB44001R#

*Oct 25 10:50:04.407: ISDN BR0/0/1 Q931: RX <- SETUP pd = 8 callref = 0x42

Sending Complete

Bearer Capability i = 0x8090A3

Standard = CCITT

Transfer Capability = Speech

Transfer Mode = Circuit

Transfer Rate = 64 kbit/s

Channel ID i = 0x89

Exclusive, B1

Called Party Number i = 0x81, '2525'

Plan:ISDN, Type:Unknown

High Layer Compat i = 0x9181

*Oct 25 10:50:04.511: ISDN BR0/0/1 Q931: TX -> CALL_PROC pd = 8 callref = 0xC2

Channel ID i = 0x89

Exclusive, B1

*Oct 25 10:50:04.531: ISDN BR0/0/1 Q931: TX -> ALERTING pd = 8 callref = 0xC2

Progress Ind i = 0x8088 - In-band info or appropriate now available

NB44001R#

*Oct 25 10:50:10.627: ISDN BR0/0/1 Q931: RX <- RELEASE pd = 8 callref = 0x42

Cause i = 0x8790 - Normal call clearing

*Oct 25 10:50:10.675: ISDN BR0/0/1 Q931: TX -> RELEASE_COMP pd = 8 callref = 0xC2

NB44001R#

*Oct 25 10:50:12.747: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/1, TEI 0 changed to down

*Oct 25 10:50:12.799: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/1, TEI 0 changed to up

Regards.

Julien.

Silver

Re: ISDN BRI switch-type configuration

What does the debug isdn q931 look like when the GW goes into SRST fallback mode?

Ajaz

Community Member

Re: ISDN BRI switch-type configuration

Layer 1 deactivated, deb isdn q921 show layer 1 error, TEI does not come up, no incoming/outgoing calls possible.

I can't take a trace for the moment.

Is there any problems with vn3 on 12.4 main relase ?

Julien.

Silver

Re: ISDN BRI switch-type configuration

If you would like to eliminate if this is indeed a IOS issue in respect the the switch-type selection we can do the following:

1) Force GW into fallback (SRST)

2) Manually configure the switch-type vn3

3) Check ISDN status

4) Do not reload

I'm sure we'll get to the bottom of this even if it does turn out to be a bug...

Ajaz

Community Member

Re: ISDN BRI switch-type configuration

I found the "solution", remove "mgcp config-server" from the gw config after configuring all parameters from CUCM administration. It should no more override the isdn switch-type on the gw !!!

Julien.

Cisco Employee

Re: ISDN BRI switch-type configuration

I just did a check on a Call Manager 5.0 server and could only see BRI-NET3 as a pulldown for BRI switch types.

When the gateway re-registers, it would pull down the config off the CCM and since it only knows about BRI-NET3, this is why it was overwriting your config.

As the D channel is backauled to the Call Manager, technically this is an unsupported configuration as the VN3 signaling/messages may not be fully understand by the ISDN protocol stack inside CCM. Annecdotal reports are that VN3 is very close to Net3, so if it works and there are no issues then we should leave it at that :-)

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