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 “$paratext>” section.) 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.
PortFast Troubleshooting
PortFast is a feature that you typically enable for a port or interface that connects to a host. When the link comes up on this port, the bridge skips the first stages of the STA and directly transitions to forwarding mode.
If you use the PortFast feature on switch ports or interfaces that connect to other switches, hubs, or routers, a network loop might get created. If the looped traffic is heavy, the bridge might experience problems with the successful transmission of the BPDU that stops the loop. This problem could delay convergence, or in extreme cases, bring down the network.
Caution Do not use the PortFast feature on switch ports or interfaces that connect to other switches, hubs, or routers. Otherwise, you might create a network loop.
For details, see the “PortFast Configuration Error” section in the
Spanning Tree Protocol Problems and Related Design Considerations
document.
ATM Troubleshooting Commands
Use the following commands to troubleshoot your ATM interface.
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. Example 14-2 shows sample command output.
Example 14-2 Viewing the 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 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 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 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 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, reliability 255/255. txload 1/255, rxload 1/255 Encapsulation PPP, loopback not set DTR is pulsed for 5 seconds on reset
Table 14-1
describes possible command output for the
show interface
command.
Table 14-1 show interface Command Output Description
|
|
|
ATM 0 is up, line protocol is up
|
The 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.
|
ATM 0.
n
is up, line protocol is up
|
The specified ATM subinterface is up and operating correctly.
|
ATM 0.
n
is administratively down, line protocol is down
|
The specified ATM subinterface has been disabled with the shutdown command.
|
ATM 0.
n
is down, line protocol is down
|
The 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 up
|
The specified Fast Ethernet interface is connected to the network and operating correctly.
|
Fast Ethernet
n
is up, line protocol is down
|
The specified Fast Ethernet interface has been correctly configured and enabled, but the Ethernet cable might be disconnected from the LAN.
|
Fast Ethernet
n
is administratively down, line protocol is down
|
The specified Fast Ethernet interface has been disabled with the
shutdown
command, and the interface is disconnected.
|
|
Dialer
n
is up, line protocol is up
|
The 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.
|
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 0 AAL enabled: AAL5 AAL2, Maximum VCs: 23, Current VCCs: 0 PLIM Type: ADSL - 4608Kbps Upstream, DMT, TX clocking: LINE 0 input, 0 output, 0 IN fast, 0 OUT fast
Table 14-2
describes some of the fields shown in the command output.
Table 14-2 show atm interface Command Output Description
|
|
ATM interface
|
Interface number. Always 0 for the Cisco 1800 fixed-configuration routers.
|
AAL enabled
|
Type of AAL enabled. The Cisco 1800 fixed-configuration routers support AAL5.
|
Maximum VCs
|
Maximum number of virtual connections this interface supports.
|
Current VCCs
|
Number of active virtual channel connections (VCCs).
|
Maximum Transmit
Channels
|
Maximum number of transmit channels.
|
Max Datagram Size
|
Configured maximum number of bytes in the largest datagram.
|
PLIM Type
|
Physical layer interface module (PLIM) type.
|
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 use
debug
commands during a Telnet session on your router, enter the
terminal monitor
command.
Caution Debugging 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
ATM errors debugging is on 01:32:02:ATM(ATM0.2):VC(3) Bad SAP received 4500 01:32:04:ATM(ATM0.2):VC(3) Bad SAP received 4500 01:32:06:ATM(ATM0.2):VC(3) Bad SAP received 4500 01:32:08:ATM(ATM0.2):VC(3) Bad SAP received 4500 01:32:10:ATM(ATM0.2):VC(3) Bad SAP received 4500
debug atm events Command
Use the
debug atm
events
command to display events that occur on the ATM interface processor and to diagnose problems in an ATM network. This command provides an overall picture of the stability of the network. The
no
form of this command disables debugging output.
If the interface is successfully communicating with the Digital Subscriber Line Access Multiplexer (DSLAM) at the telephone company, the modem state is 0x10. If the interface is not communicating with the DSLAM, the modem state is 0x8. Example 14-5 shows an ADSL line that is up and communicating successfully. Example 14-6 shows an ADSL line that is not communicating correctly. Note that the modem state does not transition to 0x10.
Example 14-5 Viewing ATM Interface Processor Events—Success
00:02:57: DSL: Send ADSL_OPEN command. 00:02:57: DSL: Using subfunction 0xA 00:02:57: DSL: Using subfunction 0xA 00:02:57: DSL: Sent command 0x5 00:02:57: DSL: Received response: 0x26 00:02:57: DSL: Unexpected response 0x26 00:02:57: DSL: Send ADSL_OPEN command. 00:02:57: DSL: Using subfunction 0xA 00:02:57: DSL: Using subfunction 0xA 00:02:57: DSL: Sent command 0x5 00:03:00: DSL: 1: Modem state = 0x8 00:03:02: DSL: 2: Modem state = 0x10 00:03:05: DSL: 3: Modem state = 0x10 00:03:07: DSL: 4: Modem state = 0x10 00:03:09: DSL: Received response: 0x24 00:03:09: DSL: Sent command 0x11 00:03:09: DSL: Received response: 0x61 00:03:09: DSL: Read firmware revision 0x1A04 00:03:09: DSL: Sent command 0x31 00:03:09: DSL: Received response: 0x12 00:03:09: DSL: operation mode 0x0001 00:03:09: DSL: SM: [DMTDSL_DO_OPEN -> DMTDSL_SHOWTIME]
Example 14-6 Viewing ATM Interface Processor Events—Failure
00:02:57: DSL: Send ADSL_OPEN command. 00:02:57: DSL: Using subfunction 0xA 00:02:57: DSL: Using subfunction 0xA 00:02:57: DSL: Sent command 0x5 00:02:57: DSL: Received response: 0x26 00:02:57: DSL: Unexpected response 0x26 00:02:57: DSL: Send ADSL_OPEN command. 00:02:57: DSL: Using subfunction 0xA 00:02:57: DSL: Using subfunction 0xA 00:02:57: DSL: Sent command 0x5 00:03:00: DSL: 1: Modem state = 0x8 00:03:00: DSL: 1: Modem state = 0x8 00:03:00: DSL: 1: Modem state = 0x8 00:03:00: DSL: 1: Modem state = 0x8 00:03:00: DSL: 1: Modem state = 0x8 00:03:00: DSL: 1: Modem state = 0x8
debug atm packet Command
Use the
debug atm
packet
command to display all process-level ATM packets for both outbound and inbound packets. The output reports information online when a packet is received or a transmission is attempted. The
no
form of this command disables debugging output.
Caution Because the
debug atm packet command generates a significant amount of output for every packet processed, use it only when network traffic is low, so that other system activities are not adversely affected.
The command syntax is:
debug atm
packet
[
interface atm
number
[
vcd
vcd-number
] [
vc
vpi/vci number]]
no debug atm
packet
[
interface atm
number
[
vcd
vcd-number
] [vc vpi/vci number]]
where the keywords are defined as follows:
interface atm
number
(Optional) ATM interface or subinterface number.
vcd
vcd-number
(Optional) Number of the virtual circuit designator (VCD).
vc
vpi/vci number
VPI/VCI value of the ATM PVC.
Example 14-7 shows a sample output.
Example 14-7 Viewing ATM Packet Processing
VCD:0x1 VPI:0x1 VCI:0x64 DM:0x0 SAP:AAAA CTL:03 OUI:000000 TYPE:0800 Length:0x70 01:23:48:4500 0064 0008 0000 FF01 9F80 0E00 0010 0E00 0001 0800 A103 0AF3 17F7 0000 01:23:48:0000 004C BA10 ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD 01:23:48:ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD 01:23:48:ABCD ABCD ABCD ABCD ABCD VCD:0x1 VPI:0x1 VCI:0x64 Type:0x0 SAP:AAAA CTL:03 OUI:000000 TYPE:0800 Length:0x70 01:23:48:4500 0064 0008 0000 FE01 A080 0E00 0001 0E00 0010 0000 A903 0AF3 17F7 0000 01:23:48:0000 004C BA10 ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD 01:23:48:ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD ABCD 01:23:48:ABCD ABCD ABCD ABCD ABCD
Table 14-3
describes some of the fields shown in the
debug atm packet
command output.
Table 14-3 debug atm packet Command Output Description
|
|
ATM0
|
Interface that is generating the packet.
|
(O)
|
Output packet. (I) would mean receive packet.
|
VCD: 0x
n
|
Virtual circuit associated with this packet, where
n
is some value.
|
VPI: 0x
n
|
Virtual path identifier for this packet, where
n
is some value.
|
DM: 0x
n
|
Descriptor mode bits, where
n
is some value.
|
Length:
n
|
Total length of the packet (in bytes) including the ATM headers.
|
Recovering a Lost Password
To recover a lost enable or lost enable-secret password:
1. Change the Configuration Register
2. Reset the Router
3. Reset the Password and Save Your Changes (for lost enable secret passwords only)
4. Reset the Configuration Register Value
Note Recovering a lost password is only possible when you are connected to the router through the console port. These procedures cannot be performed through a Telnet session.
Tip See the “Hot Tips” section on Cisco.com for additional information on replacing enable secret passwords.
Change the Configuration Register
To change a configuration register, follow these steps:
Step 1 Connect an ASCII terminal or a PC running a terminal emulation program to the CONSOLE port on the rear panel of the router.
Step 2 Configure the terminal to operate at 9600 baud, 8 data bits, no parity, and 1 stop bit.
Step 3 At the privileged EXEC prompt (r
outer_name
#), enter the
show version
command to display the existing configuration register value (shown in bold at the bottom of this output example):
Cisco IOS Software, C180X Software (C180X-ADVENTERPRISEK9-M), Version 12.4(1.8)PI2c ENGINEERING WEEKLY BUILD, synced to haw_t BASE_LABEL_OF_V124_2_T_THROTTLE Copyright (c) 1986-2005 by Cisco Systems, Inc. Compiled Fri 27-May-05 16:14 by ccai ROM: System Bootstrap, Version 12.3(8r)YH4, RELEASE SOFTWARE (fc1) ng-esw1-uut1 uptime is 1 hour, 21 minutes System returned to ROM by power-on System image file is "flash:bootimage.ng-esw1-uut1" This product contains cryptographic features and is subject to United States and local country laws governing import, export, transfer and use. Delivery of Cisco cryptographic products does not imply third-party authority to import, export, distribute or use encryption. Importers, exporters, distributors and users are responsible for compliance with U.S. and local country laws. By using this product you agree to comply with applicable laws and regulations. If you are unable to comply with U.S. and local laws, return this product immediately. A summary of U.S. laws governing Cisco cryptographic products may be found at: http://www.cisco.com/wwl/export/crypto/tool/stqrg.html If you require further assistance please contact us by sending email to Cisco 1801 (MPC8500) processor (revision 0x200) with 118784K/12288K bytes of memory. Processor board ID FHK091412QA, with hardware revision 0000 9 FastEthernet interfaces 1 ISDN Basic Rate interface 31360K bytes of ATA CompactFlash (Read/Write) Configuration register is 0x2102
Step 4 Record the setting of the configuration register.
Step 5 Enter the
config-register
value
command to set the new configuration register value. For example, to enable the break setting (indicated by the value of bit 8 in the configuration register), enter the
config-register 0x01
command from privileged EXEC mode.
-
Break enabled—Bit 8 is set to 0.
-
Break disabled (default setting)—Bit 8 is set to 1.
Reset the Router
To reset the router, follow these steps:
Step 1 If break is enabled, go to Step 2. If break is disabled, turn the router off (O), wait 5 seconds, and turn it on (|) again. Within 60 seconds, press the
Break
key. The terminal displays the ROM monitor prompt. Go to Step 3.
Note Some terminal keyboards have a key labeled Break. If your keyboard does not have a Break key, see the documentation that came with the terminal for instructions on how to send a break.
Step 2 Press break. The terminal displays the following prompt:
Step 3 Enter
confreg 0x142
to reset the configuration register:
Step 4 Initialize the router by entering the
reset
command:
The router cycles its power, and the configuration register is set to 0x142. The router uses the boot ROM system image, indicated by the system configuration dialog:
--- System Configuration Dialog ---
Step 5 Enter
no
in response to the prompts until the following message is displayed:
Press RETURN to get started!
Step 6 Press
Return
. The following prompt appears:
Step 7 Enter the enable command to enter enable mode. Configuration changes can be made only in enable mode:
The prompt changes to the privileged EXEC prompt:
Step 8 Enter the
show startup-config
command to display an enable password in the configuration file:
Router# show startup-config
If you are recovering an enable password, omit the following “Reset the Password and Save Your Changes” section, and complete the password recovery process by performing the steps in the “Reset the Configuration Register Value” section.
If you are recovering an enable secret password, it is not displayed in the
show startup-config
command output. Complete the password recovery process by performing the steps in the following “Reset the Password and Save Your Changes” section.
Reset the Password and Save Your Changes
To reset your password and save the changes, follow these steps:
Step 1 Enter the
configure terminal
command to enter global configuration mode:
Router# configure terminal
Step 2 Enter the
enable secret
command to reset the enable secret password in the router:
Router(config)# enable secret password
Step 3 Enter
exit
to exit global configuration mode:
Step 4 Save your configuration changes:
Router# copy running-config startup-config
Reset the Configuration Register Value
To reset the configuration register value after you have recovered or reconfigured a password, follow these steps:
Step 1 Enter the
configure terminal
command to enter global configuration mode:
Router# configure terminal
Step 2 Enter the
configure register
command and the original configuration register value that you recorded.
Router(config)# config-reg value
Step 3 Enter
exit
to exit configuration mode:
Note To return to the configuration being used before you recovered the lost enable password, do not save the configuration changes before rebooting the router.
Step 4 Reboot the router, and enter the recovered password.