[cisco-voip] ISDN PRI channel stuck in busy status?

[Kelemen Zoltan]

Hi!

We have a CCME, 4.2(0), IOS: 12.4(11)XW6 with a partial E1.

When examining some complaints, that the client was unable to place more 
than a few calls outside and most of incoming calls failed to reach 
them, I found the ISDN interface with more busy channels than active 
voice calls.

Below I attached an example, where channel 9 is stuck (on channel 10 I 
might have just catched a call that just disconnected, but channel 9 was 
continuously stuck busy with no active call on it.).

This is relatively light, since there's still 9 other channels for light 
traffic, but I have seen this interface with  8 or even all ten channels 
stuck.  So far I  haven't found  any other way to solve it but to  
restart the  serial interface.

Any ideas what could be going wrong? Or at least if it's possible to 
recover a channel from that state, other than restarting the interface?

Thanks,
  Zoltan


ccme#sh isdn stat ser 0/0/0:15
Global ISDN Switchtype = primary-net5
ISDN Serial0/0/0:15 interface
    dsl 0, interface ISDN Switchtype = primary-net5
    Layer 1 Status:
    ACTIVE
    Layer 2 Status:
    TEI = 0, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED
    Layer 3 Status:
    1 Active Layer 3 Call(s)
    CCB:callid=2707, sapi=0, ces=0, B-chan=9, calltype=VOICE
    CCB:callid=A622, sapi=0, ces=0, B-chan=8, calltype=VOICE
    CCB:callid=A627, sapi=0, ces=0, B-chan=10, calltype=VOICE
    CCB:callid=270E, sapi=0, ces=0, B-chan=7, calltype=VOICE
    Active dsl 0 CCBs = 4
    The Free Channel Mask:  0x8000003F
    Number of L2 Discards = 0, L2 Session ID = 113


        
ccme#sh isdn serv ser 0/0/0:15
PRI Channel Statistics:
ISDN Se0/0/0:15, Channel [1-31]
  Configured Isdn Interface (dsl) 0
   Channel State (0=Idle 1=Proposed 2=Busy 3=Reserved 4=Restart 
5=Maint_Pend)
    Channel :  1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    State   :  0 0 0 0 0 0 2 2 2 2 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 
3 3
   Service State (0=Inservice 1=Maint 2=Outofservice 8=MaintPend 9=OOSPend)
    Channel :  1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    State   :  0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 
2 2



ccme#sh voice call 0/0/0:15  
0/0/0:15 1 -          -  -                    
0/0/0:15 2 -          -  -                    
0/0/0:15 3 -          -  -                    
0/0/0:15 4 -          -  -                    
0/0/0:15 5 -          -  -                    
0/0/0:15 6 -          -  -                    
0/0/0:15 7
      vtsp level 0 state = S_CONNECT
callid 0x270E B07 state S_TSP_CONNECT clld 100 cllg 7518XXXXX
0/0/0:15 8
      vtsp level 0 state = S_CONNECT
callid 0xA622 B08 state S_TSP_CONNECT clld 07499XXXXX cllg 113
0/0/0:15 9 -          -  -                    
0/0/0:15 10-          -  -                    

-------------------------------- configuration

controller E1 0/0/0
 framing NO-CRC4
 clock source internal
 pri-group timeslots 1-10,16
!
interface Serial0/0/0:15
 no ip address
 encapsulation hdlc
 isdn switch-type primary-net5
 isdn overlap-receiving
 isdn incoming-voice voice
 isdn send-alerting
 isdn sending-complete
 no cdp enable
!