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Step 8ip address negotiated
Example:
Router(config-if)# ip address negotiatedRouter(config-if)#
Specifies that the IP address for the interface is 
obtained through PPP/IPCP (IP Control Protocol) 
address negotiation. The IP address is obtained 
from the peer.
Step 9encapsulation encapsulation-type
Example:
Router(config-if)# encapsulation ppp
Router(config-if)#
Sets the encapsulation type to PPP for the 
interface.
Step 10dialer pool number
Example:
Router(config-if)# dialer pool 1
Router(config-if)#
Specifies the dialer pool to be used. 
In the example, the dialer pool 1 setting associates 
the dialer 0 interface with the BRI0 interface 
because the BRI0 dialer pool-member value is 1.
Step 11dialer string dial-string[:isdn-subaddress]
Example:
Router(config-if)# dialer string 384040
Router(config-if)#
Specifies the telephone number to be dialed.
Step 12dialer-group group-number
Example:
Router(config-if)# dialer group 1
Router(config-if)#
Assigns the dialer interface to a dialer group 
(1–10).
Step 13exit
Example:
Router(config-if)# exitRouter(config)#
Exits dialer 0 interface configuration mode, and 
enters global configuration mode.
Step 14dialer-list dialer-group protocol protocol-name 
{permit | deny | list access-list-number | 
access-group} 
Example:
Router(config)# dialer-list 1 protocol ip 
permit
Router(config)#
Creates a dialer list for packets of interest to be 
forwarded through the specified interface dialer 
group. 
In the example, dialer-list 1 corresponds to 
dialer-group 1.
For details about this command and additional 
parameters that can be set, see the 
Cisco IOS Dial 
Technologies Command Reference.
Command Purpose 
						

							 
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Configure the Aggregator and ISDN Peer Router
The aggregator is typically a concentrator router where your Cisco router ATM PVC terminates. In the 
configuration example shown below, the aggregator is configured as a PPPoE server to correspond with 
the Cisco
 876 router configuration example that is given in this chapter.
The ISDN peer router is any router that has an ISDN interface and can communicate through a public 
ISDN network to reach your Cisco router ISDN interface. The ISDN peer router provides Internet access 
for your Cisco router during the ATM network downtime.
! This portion of the example configures the aggregator.
vpdn enable
no vpdn logging!
vpdn-group 1
 accept-dialin protocol pppoe
 virtual-template 1
!interface Ethernet3
 description “4700ref-1”
 ip address 40.1.1.1 255.255.255.0 media-type 10BaseT
!
interface Ethernet4
 ip address 30.1.1.1 255.255.255.0 media-type 10BaseT
!
interface Virtual-Template1 ip address 22.0.0.2 255.255.255.0
 ip mtu 1492
 peer default ip address pool adsl!
interface ATM0
 no ip address pvc 1/40
 encapsulation aal5snap
 protocol pppoe!
no atm limi-keepalive
!ip local pool adsl 22.0.0.1
ip classless
ip route 0.0.0.0 0.0.0.0 22.0.0.1 50ip route 0.0.0.0 0.0.0.0 30.1.1.2.80
! This portion of the example configures the ISDN peer.isdn switch-type basic-net3
!
interface Ethernet0 ip address 30.1.1.2 255.0.0.0 
!
interface BRI0 description “to 836-dialbackup”
 no ip address
 encapsulation ppp dialer pool-member 1
 isdn switch-type basic-net3
! 
						

							 
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interface Dialer0 ip address 192.168.2.2 255.255.255.0
 encapsulation ppp
 dialer pool 1 dialer string 384020
 dialer-group 1
 peer default ip address pool isdn!
ip local pool isdn 192.168.2.1
ip http serverip classless
ip route 0.0.0.0 0.0.0.0 192.168.2.1
ip route 40.0.0.0 255.0.0.0 30.1.1.1!
dialer-list 1 protocol ip permit
! 
						

							 
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							CH A P T E R
 
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14
Troubleshooting
Use the information in this chapter to help isolate problems you might encounter or to rule out the router 
as the source of a problem. This chapter contains the following sections:
 Getting Started
 Before Contacting Cisco or Your Reseller
 ADSL Troubleshooting
 SHDSL Troubleshooting
 ATM Troubleshooting Commands
 Software Upgrade Methods
 Recovering a Lost Password
 Managing Your Router with SDM
Getting Started
Before troubleshooting a software problem, you must connect a terminal or PC to the router using the 
light-blue console port. (For information on making this connection, see the documentation listed in the 
“Related Documents” section on page 14.) With a connected terminal or PC, you can view status 
messages from the router and enter commands to troubleshoot a problem.
You can also remotely access the interface (Ethernet, ADSL, or telephone) by using Telnet. The Telnet 
option assumes that the interface is up and running.
Before Contacting Cisco or Your Reseller
If you cannot locate the source of a problem, contact your local reseller for advice. Before you call, you 
should have the following information ready:
 Chassis type and serial number
 Maintenance agreement or warranty information
 Type of software and version number 
 Date you received the hardware
 Brief description of the problem
 Brief description of the steps you have taken to isolate the problem 
						

							 
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  ADSL Troubleshooting
ADSL Troubleshooting
If you experience trouble with the ADSL connection, verify the following:
 The ADSL line is connected and is using pins 3 and 4. For more information on the ADSL 
connection, see the hardware guide for your router.
 The ADSL CD LED is on. If it is not on, the router may not be connected to the DSL access 
multiplexer (DSLAM). For more information on the ADSL LEDs, see the hardware installation 
guide specific for your router.
 The correct Asynchronous Transfer Mode (ATM) virtual path identifier/virtual circuit identifier 
(VPI/VCI) is being used.
 The DSLAM supports discrete multi-tone (DMT) Issue 2.
 The ADSL cable that you connect to the Cisco router must be 10BASE-T Category 5, unshielded 
twisted-pair (UTP) cable. Using regular telephone cable can introduce line errors.
SHDSL Troubleshooting
Symmetrical high-data-rate digital subscriber line (SHDSL) is available on Cisco 878 and Cisco 1803 
router models. If you experience trouble with the SHDSL connection, verify the following:
 The SHDSL line is connected and using pins 3 and 4. For more information on the G.SHDSL 
connection, see the hardware guide for your router.
 The G.SHDSL LED is on. If it is not on, the router may not be connected to the DSL access 
multiplexer (DSLAM). For more information on the G.SHDSL LED, see the hardware installation 
guide specific for your router.
 The correct asynchronous transfer mode (ATM) virtual path identifier/virtual circuit identifier 
(VPI/VCI) is being used.
 The DSLAM supports the G.SHDSL signaling protocol.
Use the show controllers dsl 0 command in EXEC mode to view an SHDSL configuration.
ATM Troubleshooting Commands
Use the following commands to troubleshoot your ATM interface.
 ping atm interface Command
 show interface Command
 show atm interface Command
 debug atm Commands 
						

							 
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ping atm interface Command
Use the ping atm interface command to determine whether a particular PVC is in use. The PVC does 
not need to be configured on the router to use this command. 
Example 14-1 shows the use of this 
command to determine whether PVC 8/35 is in use.
Example 14-1 Determining If a PVC Is in Use
Router# ping atm interface atm 0 8 35 seg-loopback 
Type escape sequence to abort.
Sending 5, 53-byte segment OAM echoes, timeout is 2 seconds:
!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 148/148/148 ms
This command sends five OAM F5 loopback packets to the DSLAM (segment OAM packets). If the PVC 
is configured at the DSLAM, the ping is successful.
To test whether the PVC is being used at the aggregator, enter the following command:
Router# ping atm interface atm 0 8 35 end-loopback 
Type escape sequence to abort.Sending 5, 53-byte end-to-end OAM echoes, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 400/401/404 ms
This command sends end-to-end OAM F5 packets, which are echoed back by the aggregator.
show interface Command
Use the show interface command to display the status of all physical ports (Ethernet and ATM) and 
logical interfaces on the router. 
Ta b l e 14-1 describes messages in the command output.
Example 14-2 Viewing Status of Selected Interfaces
Router# show interface atm 0
ATM0 is up, line protocol is up   Hardware is PQUICC_SAR (with Alcatel ADSL Module)
  Internet address is 14.0.0.16/8
  MTU 1500 bytes, sub MTU 1500, BW 640 Kbit, DLY 80 usec,      reliability 40/255, txload 1/255, rxload 1/255
  Encapsulation ATM, loopback not set
  Keepalive not supported   Encapsulation(s):AAL5, PVC mode
  10 maximum active VCs, 1 current VCCs
  VC idle disconnect time:300 seconds  Last input 01:16:31, output 01:16:31, output hang never
  Last clearing of show interface counters never
  Input queue:0/75/0 (size/max/drops); Total output drops:0  Queueing strategy:Per VC Queueing
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec     512 packets input, 59780 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 1024 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 
						

							 
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     426 packets output, 46282 bytes, 0 underruns     0 output errors, 0 collisions, 2 interface resets
     0 output buffer failures, 0 output buffers swapped out
Router# show interface fastethernet 0
Ethernet0 is up, line protocol is up 
Hardware is PQUICC Ethernet, address is 0000.Oc13.a4db (bia0010.9181.1281)
Internet address is 170.1.4.101/24
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, reliability 255/255., txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Router# show interface dialer 1
Dialer 1 is up, line protocol is up Hardware is Dialer interface
Internet address is 1.1.1.1/24
MTU 1500 bytes, BW 100000 Kbit, DLY 100000 usec, reliability255/255. txload 1/255, rxload 1/255
Encapsulation PPP, loopback not set
Keepalive set (10 sec)DTR is pulsed for 5 seconds on reset
LCP Closed
Ta b l e 14-1 describes possible command output for the show interface command. 
Ta b l e 14-1 show interface Command Output Description 
Output Cause
For ATM Interfaces
ATM 0 is up, line protocol is upThe ATM line is up and operating correctly.
ATM 0 is down, line protocol is down The ATM interface has been disabled with the 
shutdown command. 
or
 The ATM line is down, possibly because the 
ADSL cable is disconnected or because the 
wrong type of cable is connected to the ATM 
port.
AT M  0 .n is up, line protocol is up The specified ATM subinterface is up and operating 
correctly.
AT M  0 .n is administratively down, line protocol 
is downThe specified ATM subinterface has been disabled 
with the shutdown command.
AT M  0 .n is down, line protocol is downThe specified ATM subinterface is down, possibly 
because the ATM line has been disconnected (by the 
service provider).
For Fast Ethernet Interfaces
Fast Ethernet n is up, line protocol is upThe specified Fast Ethernet interface is connected to 
the network and operating correctly.
Fast Ethernet n is up, line protocol is downThe specified Fast Ethernet interface has been 
correctly configured and enabled, but the Ethernet 
cable might be disconnected from the LAN. 
						

							 
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show atm interface Command
To display ATM-specific information about an ATM interface, use the show atm interface atm 0 
command from privileged EXEC mode, as shown in 
Example 14-3.
Example 14-3 Viewing Information About an ATM Interface
Router# show atm interface atm 0Interface ATM0:
AAL enabled: AAL5 , Maximum VCs:11, Current VCCs:0
Maximum Transmit Channels:0
Max. Datagram Size:1528
PLIM Type:INVALID - 640Kbps, Framing is INVALID,DS3 lbo:short, TX clocking:LINE
0 input, 0 output, 0 IN fast, 0 OUT fast
Avail bw = 640 Config. is ACTIVE
Ta b l e 14-2 describes some of the fields shown in the command output.
Fast Ethernet n is administratively down, line 
protocol is downThe specified Fast Ethernet interface has been 
disabled with the shutdown command, and the 
interface is disconnected.
For Dialer Interfaces
Dialer n is up, line protocol is upThe specified dialer interface is up and operating 
correctly.
Dialer n is down, line protocol is down This is a standard message and may not indicate 
anything is actually wrong with the 
configuration.
or
 If you are having problems with the specified 
dialer interface, this can mean it is not 
operating, possibly because the interface has 
been brought down with the shutdown 
command, or the ADSL cable is disconnected.
Table 14-1 show interface Command Output Description (continued)
Output Cause
Ta b l e 14-2 show atm interface Command Output Description 
FieldDescription
AT M  i n t e r f a c eInterface number. Always 0 for the Cisco 850 and Cisco 870 series access routers.
AAL enabledType of AAL enabled. The Cisco 850 and Cisco 870 series access routers support 
AAL5.
Maximum VCsMaximum number of virtual connections this interface supports.
Current VCCsNumber of active virtual channel connections (VCCs). 
						

							 
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debug atm Commands
Use the debug commands to troubleshoot configuration problems that you might be having on your 
network. The debug commands provide extensive, informative displays to help you interpret any 
possible problems. 
Guidelines for Using Debug Commands
Read the following guidelines before using debug commands to ensure appropriate results.
 All debug commands are entered in privileged EXEC mode.
 To view debugging messages on a console, enter the logging console debug command.
 Most debug commands take no arguments.
 To disable debugging, enter the undebug all command.
 To  u s e  debug commands during a Telnet session on your router, enter the terminal monitor 
command.
CautionDebugging is assigned a high priority in your router CPU process, and it can render your router unusable. 
For this reason, use debug commands only to troubleshoot specific problems. The best time to use debug 
commands is during periods of low network traffic so that other activity on the network is not adversely 
affected.
You can find additional information and documentation about the debug commands in the Cisco IOS 
Debug Command Reference.
debug atm errors Command
Use the debug atm errors command to display ATM errors. The no form of this command disables 
debugging output. 
Example 14-4 shows a sample output.
Example 14-4 Viewing ATM Errors
Router# debug atm errorsATM errors debugging is on
Router#
01:32:02:ATM(ATM0.2):VC(3) Bad SAP received 450001:32:04:ATM(ATM0.2):VC(3) Bad SAP received 4500
01:32:06:ATM(ATM0.2):VC(3) Bad SAP received 4500
Maximum 
Transmit
 
Channels
Maximum number of transmit channels.
Max Datagram 
SizeConfigured maximum number of bytes in the largest datagram.
PLIM TypePhysical layer interface module (PLIM) type.
Table 14-2 show atm interface Command Output Description (continued)
Field Description