ISDN: Strange behaviour

[Michael Kiessling]

Hi all,

anyone seen something like this before:

This is the router we are using as voice gatway:

Cisco Router 2801

IOS: c2801-advipservicesk9-mz.124-24.T2

2 FastEthernet interfaces
2 ISDN Basic Rate interfaces     <----------- Two ISDN lines
1 terminal line
1 Virtual Private Network (VPN) Module
2 Voice FXS interfaces
1 DSP, 8 Voice resources
1 cisco Internal Service Module(s)
   Cisco Unity Express 7.1.4 in slot 0

And this is our very basic setup:

interface BRI0/0/0
no ip address
isdn switch-type basic-net3
isdn overlap-receiving
isdn point-to-point-setup
isdn incoming-voice voice
isdn static-tei 0
!
interface BRI0/0/1
no ip address
isdn switch-type basic-net3
isdn overlap-receiving
isdn point-to-point-setup
isdn incoming-voice voice
isdn static-tei 0

And now the mystery:

If we make an incoming call we will see it on both BRI interfaces simultaneously:

Jun 15 12:28:10: ISDN BR0/0/0 Q931: RX <- SETUP pd = 8  callref = 0x3D   <-------- BRI0/0/0
        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
        Calling Party Number i = 0x1081, 'xxxxxxxxx3'
                Plan:Unknown, Type:International
        Called Party Number i = 0x81, '5124'
                Plan:ISDN, Type:Unknown
        High Layer Compat i = 0x9181
Jun 15 12:28:10: ISDN BR0/0/1 Q931: RX <- SETUP pd = 8  callref = 0x3D    <-------- BRI0/0/1
        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
        Calling Party Number i = 0x1081, 'xxxxxxxxx3'
                Plan:Unknown, Type:International
        Called Party Number i = 0x81, '5124'
                Plan:ISDN, Type:Unknown
        High Layer Compat i = 0x9181
Jun 15 12:28:10: ISDN BR0/0/0 Q931: TX -> CALL_PROC pd = 8  callref = 0xBD
        Channel ID i = 0x89
                Exclusive, B1
Jun 15 12:28:10: ISDN BR0/0/1 Q931: TX -> CALL_PROC pd = 8  callref = 0xBD
        Channel ID i = 0x89
                Exclusive, B1
Jun 15 12:28:10: ISDN BR0/0/0 Q931: TX -> ALERTING pd = 8  callref = 0xBD
Jun 15 12:28:10: ISDN BR0/0/1 Q931: TX -> ALERTING pd = 8  callref = 0xBD
Jun 15 12:28:14: ISDN BR0/0/0 Q931: TX -> CONNECT pd = 8  callref = 0xBD
        Channel ID i = 0x89
                Exclusive, B1
Jun 15 12:28:15: ISDN BR0/0/0 Q931: RX <- RELEASE pd = 8  callref = 0x3D
        Cause i = 0x87A9 - Temporary failure
Jun 15 12:28:15: ISDN BR0/0/1 Q931: RX <- RELEASE pd = 8  callref = 0x3D
        Cause i = 0x87A9 - Temporary failure
Jun 15 12:28:15: ISDN BR0/0/1 Q931: TX -> RELEASE_COMP pd = 8  callref = 0xBD
Jun 15 12:28:16: ISDN BR0/0/0 Q931: TX -> RELEASE_COMP pd = 8  callref = 0xBD
Jun 15 12:28:16: ISDN BR0/0/0 **ERROR**: L2_AdvanceVA: TX_ack_queue empty     <------- Error: The call is disconnected
Jun 15 12:28:16: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/0, TEI 0 changed to down
Jun 15 12:28:16: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/1, TEI 0 changed to down
Jun 15 12:28:16: ISDN BR0/0/0 Q931: Ux_DLRelInd: DL_REL_IND received from L2
Jun 15 12:28:16: ISDN BR0/0/1 Q931: Ux_DLRelInd: DL_REL_IND received from L2
Jun 15 12:28:18: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/1, TEI 0 changed to up
Jun 15 12:28:20: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0/0/1, TEI 0 changed to down
Jun 15 12:28:20: ISDN BR0/0/1 Q931: Ux_DLRelInd: DL_REL_IND received from L2
Jun 15 12:28:32: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/0, TEI 0 changed to up
Jun 15 12:28:32: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0/1, TEI 0 changed to up

Strange, isn't it?

Has anyone seen somthin similar?

Is it possible that the Telco switch has a configuration problem?

Many thanks,

Michael

[Aaron Harrison · Accepted solution]

Hi

ISDN2 NTEs typically have two ports.

It looks to me like someone has helpfully connected both ports on the router to both ports on the NTE.

You get 2 channels per port, and 2 channels per ISDN2 circuit, so there's no benefit to doing this. Shut down one port and it will probably work better; then check over the cabling.

If you have two BRI circuits, connect one to each port on the router.

If you have one two-channel BRI, then connect it to a single port.

Regards

Aaron

Please rate helpful posts...

[Michael Kiessling]

Hi Aaron,

thank you for your reply.

We should have two ISDN circuites - at least that is what we ordered (so we can have 4 phone calls simultaniously).

I will have someone to check the cabeling. It's not impossible that someone did a big mistake.

I will keep you up to date.

PS: If I do a shutdown on one interface we can have incoming and outgoing phone calls (although we can have only 2 calls simultaniously)

Thank you for your hint,

Michael

[Aaron Harrison]

Hi

No problem, let us know how you get on.

Aaron

[Michael Kiessling]

Hi Aaron,

you are right! It was a cabling issue.... on site is a NTE with 5 Ports labeled 1 1 3 4 5

Port 1 and 1 use the same bus - who would have thought this? :-)

Thankys for your help.

[Aaron Harrison]

Hi Michael

Glad to hear it's fixed :-)

Aaron