ISDN Troubleshooting Commands to Know | CCNP CIT Exam Cram 2 (Exam Cram 642-831)

For the exam there are a few other commands that you need to know and understand. Here are some commands you'll need to know that haven't been covered elsewhere in the chapter:

clear interface bri
debug bri
debug dialer
show controller bri
show dialer

The following sections discuss these commands in detail.

The clear interface bri Command

The clear interface bri command followed by the BRI interface number resets the ISDN counters that are available on an ISDN interface. This will also terminate any active connection on an ISDN interface. As the following example indicates, the command has no output:

 Seans804#  clear int bri0  Seans804#

The debug bri Command

The debug bri command provides information, such as bandwidth, about the B channels used in a BRI interface.

A router can still connect if only one B channel fails. If this occurs, check for a misconfigured SPID or other interface configuration issue.

The following output demonstrates the command in action:

 Seans804#  debug bri  Basic Rate network interface debugging is on Seans804# ping 172.16.1.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds: 00:29:48: BRI: enable channel B1 00:29:48: BRI0:MC145572 state handler current state 3 actions 1 next state 3 00:29:48: BRI0:Starting activation 00:29:48: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up. 00:29:49: BRI 0 B1: Set bandwidth to 64Kb 00:29:50: %LINEPROTO-5-UPDOWN: Line protocol on Interface     BRI0:1, changed state to up 00:29:50: BRI 0 B2: Set bandwidth to 64Kb 00:29:50: BRI: enable channel B2 00:29:50: BRI0:MC145572 state handler current state 3 actions 1 next state 3 00:29:50: BRI0:Starting activation 00:29:50: %LINK-3-UPDOWN: Interface BRI0:2, changed state to up.!!! Success rate is 60 percent (3/5), round-trip min/avg/max = 36/41/52 ms 00:29:50: BRI: enable channel B2 00:29:50: BRI0:MC145572 state handler current state 3 actions 1 next state 3 00:29:50: BRI0:Starting activation 00:29:50: BRI 0 B2: Set bandwidth to 64Kb 00:29:51: %LINEPROTO-5-UPDOWN: Line protocol on Interface     BRI0:2, changed state to up

The A and B channels are used to carry the data across the active link. Any error on an activates B channel will prevent the flow of data. The above output shows a successful ISDN data transfer.

The debug dialer Command

The debug dialer command can be used to show information regarding the cause of a dialing connection problem. The following is an example of using the command:

 Seans804#  debug dialer  Dial on demand events debugging is on Seans804#  ping 172.16.1.1  Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds: 00:36:15: BRI0: Dialing cause ip (s=172.16.1.2, d=172.16.1.1) 00:36:15: BRI0: Attempting to dial 18005551001 00:36:15: %LINK-3-UPDOWN: Interface BRI0:1, changed state to up. 00:36:15: dialer Protocol up for BR0:1 00:36:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface     BRI0:1, changed state to up 00:36:15: %LINK-3-UPDOWN: Interface BRI0:2, changed state to up. !!!!! Success rate is 100 percent(5/5),                 round-trip min/avg/max=32/37/48/23/33 ms 00:36:15: dialer Protocol up for BR0:2 00:36:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface     BRI0:2, changed state to up

The debug dialer command output above shows the complete process the dialer takes when an ICMP ping is the interesting traffic activating the ISDN BRI interface.

The show controller bri Command

The show controller bri command displays the interface hardware controller information. This command is most useful when troubleshooting with Cisco's TAC, obtaining the status of an interface, and obtaining the superframe error counter information. The following is the output from this command:

 Sean804#  show controller bri  BRI unit 0:BRI unit 0 with U interface and POTS: Layer 1 internal state is ACTIVATED Layer 1 U interface is ACTIVATED. ISDN Line Information:     Current EOC commands:         RTN - Return to normal     Received overhead bits:         AIB=1, UOA=1, SCO=1, DEA=1, ACT=1, M50=1, M51=1, M60=1, FEBE=1     Errors:  [FEBE]=0, [NEBE]=0     Errors:  [Superframe Sync Loss]=0, [IDL2 Data    Transparency Loss]=0              [M4 ACT 1 -> 0]=0 BRI U MLT Timers:  [TPULSE]=0, [T75S]=0 BRI U MLT Timers:  [TPULSE]=0, [T75S]=0 Motorola MC145572 registers: NR0  = 0     NR1  = 4     NR2  = 0     NR3  = 0     NR4  = E     NR5  = 6 BR0  = F7    BR1  = 7F    BR2  = F0    BR3  = 40    BR4  = 0     BR5  = 0 BR6  = 0     BR7  = 1     BR8  = 1     BR9  = C     BR10 = 0     BR11 = C BR12 = 0     BR13 = 0     BR14 = 0     BR15 = 46 OR0  = 0     OR1  = 4     OR2  = 8     OR3  = 0     OR4  = 4     OR5  = 8 OR6  = E0    OR7  = 11    OR8  = 0     OR9  = 0 D Channel Information: Using SCC3, Microcode ver 101 idb at 0x272BF38, driver data structure at 0x273FB90 SCC Registers: General [GSMR]=0x780:0x0000003A, Protocol-specific [PSMR]=0x0 Events [SCCE]=0x0000, Mask [SCCM]=0x001F, Status [SCCS]=0x0002 Transmit on Demand [TODR]=0x0, Data Sync [DSR]=0x7E7E Interrupt Registers: Config [CICR]=0x00368481, Pending [CIPR]=0x00000640 Mask   [CIMR]=0x30061090, In-srv  [CISR]=0x00000000 Command register [CR]=0xE84 Port A [PADIR]=0x08C3, [PAPAR]=0x07CC        [PAODR]=0x0040, [PADAT]=0x0FCF Port B [PBDIR]=0x00E02E, [PBPAR]=0x0020DE        [PBODR]=0x000000, [PBDAT]=0x0053CF Port C [PCDIR]=0x000C, [PCPAR]=0x0800        [PCSO]=0x00C0,  [PCDAT]=0x0433, [PCINT]=0x0000 Port D [PDDIR]=0x001FFF, [PDPAR]=0x000000        [PDDAT]=0x001FFB SI     [SIMODE]=0x00001141,  [SIGMR]=0x04, [SISTR]=0x00        [SICR]=0x00403500 BRGC   [BRGC2]=0x000101A8,  [BRGC3]=0x00000000 SPI Mode [SPMODE]=0x3771, Events [SPIE]=0x0     Mask [SPIM]=0x0, Command [SPCOM]=0x0 SI Mode [SIMODE]=0x1141, Global [SIGMR]=0x4    Cmnd [SICMR]=0x0, Stat [SISTR]=0x0 SI Clock Route [SICR]=0x00403500 <Some Output Cut>   0 missed datagrams, 0 overruns   0 bad datagram encapsulations, 0 memory errors   0 transmitter underruns

The show dialer Command

The show dialer command displays information about DDR connections. The output from this command follows :

 Seans804#  show dialer  BRI0 - dialer type = ISDN Dial String      Successes   Failures    Last called       Last status 18005551001              2          6       00:03:36        successful 8 incoming call(s) have been screened. 0 incoming call(s) rejected for callback. BRI0:1 - dialer type = ISDN Idle timer (120 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re-enable (15 secs) Dialer state is idle BRI0:2 - dialer type = ISDN Idle timer (120 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re-enable (15 secs) Dialer state is idle

The output above shows the phone number dialed , connection successes, idle timers, and the number of calls that were accepted or rejected due to an administrative policy configuration.