ISDN BRI Layer 1 problem: flapping S interface
Marek Moszynski
I have a problem with a flapping ISDN BRI S interface on a Cisco MC3810
router, in Frankfurt (Germany). I isolated the problem to Layer 1, the
interface is flapping between states F3 to F7 and F8.
I am looking for someone who could help me identify the source of the
problem.
I include below the output of the "debug bri-interface" command for a
complete cycle. The cycle is around 2 mins long, and there are 10 secs idle
between cycles:
.Dec 14 10:01:42.190: BRI0: In state F3, Received code Level detected
.Dec 14 10:01:42.190: BRI0 : changing state to F5
.Dec 14 10:01:42.194: BRI0: In state F5, Received code Activate request
downstream, Info 2 received
.Dec 14 10:01:42.194: BRI0 : changing state to F6
.Dec 14 10:01:42.210: BRI0: In state F6, Received code Activation Indication
with Priority to 8, Info 4 received
.Dec 14 10:01:42.210: BRI0 : Sending PH-Activate to the layer 2
.Dec 14 10:01:42.210: BRI0 : changing state to F7
.Dec 14 10:01:42.214: BRI0 : attempt to stop timer t3, timer has gone
.Dec 14 10:01:42.214: BRI0: In state F7, Transmitting code Activation
Request, set Priority to 8
.Dec 14 10:01:42.214: BRI0 : Sending MPH-ERROR Indication reporting recovery
from error to layer2
.Dec 14 10:01:42.235: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0, TEI 75
changed to up
.Dec 14 10:01:42.363: BRI0: In state F7, Received code unknown code
.Dec 14 10:01:42.363: BRI0 : Unexpected indication in f7 code
.Dec 14 10:01:42.363: BRI0: In state F7, Received code Activation Indication
with Priority to 8, Info 4 received
.Dec 14 10:01:42.363: BRI0 : do nothing
.Dec 14 10:03:42.608: %ISDN-6-LAYER2DOWN: Layer 2 for Interface BR0, TEI 75
changed to down
.Dec 14 10:03:52.853: BRI0: In state F7, Received code Level detected
.Dec 14 10:03:52.853: BRI0 : changing state to F8
.Dec 14 10:03:52.853: BRI0 : Sending MPH-ERROR Indication reporting error to
layer2
.Dec 14 10:03:52.869: BRI0: In state F8, Received code Deactivate request
.Dec 14 10:03:52.869: BRI0 : attempt to stop timer t3, timer has gone
.Dec 14 10:03:52.869: BRI0 : Sending MPH-ERROR Indication reporting recovery
from error to layer2
.Dec 14 10:03:52.869: BRI0 : changing state to F3
.Dec 14 10:03:52.869: BRI0 : Starting layer 1 T4
.Dec 14 10:03:53.375: BRI0 : T4 expired
.Dec 14 10:03:53.375: BRI0 : Sending PH-DEACTIVATE to layer2
.Dec 14 10:03:53.375: BRI0 : changing state to F3
BRI: disable channel B1
BRI: disable channel B2
.Dec 14 10:03:53.375: BRI0: In state F3, Transmitting code Deactivate
indication upstream
.Dec 14 10:03:53.375: BRI0: In state F3, Received code Deactivate indication
downstream
.Dec 14 10:03:53.375: BRI0 : do nothing
BRI: disable channel B1
BRI: disable channel B2
Anyone has a clue about why this is occuring every 10secs?
Thank you in advance for any help!
Marek.
Marek Moszynski
> Only in Germany! In other places it's normal to leave layer 2 established,
> and I wouldn't recommend releasing it, because you will lose a call if it
> coincides with this happening.
>
Thank your both for your assistance and ideas. I found indeed some
information about some european switches putting L1/L2 down.
To overcome this, in a Cisco router, it is necessary to use the following
command:
isdn tei-negotiation first-call
It prevents the router to negotiate the TEI on powerup, and does it at first
call.
I applied this to the router, reset the interface, made shut/no shut, but
the interface is still flapping.
Output of "show isdn status":
Global ISDN Switchtype = basic-net3
ISDN BRI0 interface
dsl 0, interface ISDN Switchtype = basic-net3
Layer 1 Status:
ACTIVE
Layer 2 Status:
TEI = 75, Ces = 1, SAPI = 0, State = TEI_ASSIGNED
I_Queue_Len 0, UI_Queue_Len 0
Layer 3 Status:
0 Active Layer 3 Call(s)
Activated dsl 0 CCBs = 0
The Free Channel Mask: 0x80000003
Total Allocated ISDN CCBs = 0
(Notice TEI=75)
I include a recent log with q921 messages added (notice TEI=64... where does
it come from?):
.Dec 17 11:07:46.735: BRI0: In state F3, Received code Level detected
.Dec 17 11:07:46.735: BRI0 : changing state to F5
.Dec 17 11:07:46.739: BRI0: In state F5, Received code Activate request
downstream, Info 2 received
.Dec 17 11:07:46.739: BRI0 : changing state to F6
.Dec 17 11:07:46.751: BRI0: In state F6, Received code Activation Indication
with Priority to 8, Info 4 received
.Dec 17 11:07:46.751: BRI0 : Sending PH-Activate to the layer 2
.Dec 17 11:07:46.751: BRI0 : changing state to F7
.Dec 17 11:07:46.751: BRI0 : attempt to stop timer t3, timer has gone
.Dec 17 11:07:46.755: BRI0: In state F7, Transmitting code Activation
Request, set Priority to 8
.Dec 17 11:07:46.755: BRI0 : Sending MPH-ERROR Indication reporting recovery
from error to layer2
.Dec 17 11:07:46.759: ISDN BR0: L1 is IF_ACTIVE
.Dec 17 11:07:46.759: ISDN BR0: Recvd MPH_EI2_IND from L1
.Dec 17 11:07:46.839: ISDN BR0: RX <- UAf sapi = 0 tei = 64
.Dec 17 11:07:46.903: BRI0: In state F7, Received code unknown code
.Dec 17 11:07:46.903: BRI0 : Unexpected indication in f7 code
.Dec 17 11:07:46.903: BRI0: In state F7, Received code Activation Indication
with Priority to 8, Info 4 received
.Dec 17 11:07:46.903: BRI0 : do nothing
.Dec 17 11:07:56.891: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:08:07.020: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:08:17.140: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:08:27.265: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:08:37.389: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:08:47.514: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:08:57.642: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:09:07.763: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:09:17.887: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:09:28.012: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:09:38.136: ISDN BR0: RX <- RRp sapi = 0 tei = 64 nr = 0
.Dec 17 11:09:47.253: ISDN BR0: RX <- DISCp sapi = 0 tei = 64
.Dec 17 11:09:57.381: BRI0: In state F7, Received code Level detected
.Dec 17 11:09:57.381: BRI0 : changing state to F8
.Dec 17 11:09:57.381: BRI0 : Sending MPH-ERROR Indication reporting error to
layer2
.Dec 17 11:09:57.381: ISDN BR0: Recvd MPH_EI1_IND from L1
.Dec 17 11:09:57.397: BRI0: In state F8, Received code Deactivate request
.Dec 17 11:09:57.397: BRI0 : attempt to stop timer t3, timer has gone
.Dec 17 11:09:57.397: BRI0 : Sending MPH-ERROR Indication reporting recovery
from error to layer2
.Dec 17 11:09:57.397: BRI0 : changing state to F3
.Dec 17 11:09:57.397: BRI0 : Starting layer 1 T4
.Dec 17 11:09:57.413: ISDN BR0: Recvd MPH_EI2_IND from L1
.Dec 17 11:09:57.899: BRI0 : T4 expired
.Dec 17 11:09:57.899: BRI0 : Sending PH-DEACTIVATE to layer2
.Dec 17 11:09:57.899: BRI0 : changing state to F3BRI: disable channel B1
BRI: disable channel B2
.Dec 17 11:09:57.899: BRI0: In state F3, Transmitting code Deactivate
indication upstream
.Dec 17 11:09:57.903: BRI0: In state F3, Received code Deactivate indication
downstream
.Dec 17 11:09:57.903: BRI0 : do nothingBRI: disable channel B1
BRI: disable channel B2
.Dec 17 11:09:57.903: ISDN BR0: Physical layer is IF_DOWN
.Dec 17 11:09:57.903: ISDN BR0: Shutting down ME
.Dec 17 11:09:57.907: ISDN BR0: Shutting down ISDN Layer 3