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Use the information in this chapter to help isolate problems you might encounter with the Cisco 827 routers or to rule out the router as the source of the problem. This chapter contains the following sections:
Before troubleshooting a software problem, you must connect a terminal or PC to the router via the light-blue console port. (For information on making this connection, see the Cisco 827 Routers Hardware Installation Guide.) With a connected terminal or PC, you can read 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.
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:
This section describes some ADSL troubleshooting checks that you can perform if the router is not working properly. If you experience trouble with the ADSL connection, make sure to verify the following:
This section describes some ATM troubleshooting commands.
Use the show interface command to display the status of all physical ports (Ethernet and ATM) and logical interfaces on the router. Significant messages in the command output are shown in bold. Significant messages are described in Table 4-1.
820-uut2#sh int atm0
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
426 packets output, 46282 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
0 output buffer failures, 0 output buffers swapped out
820-uut2#sh int eth0
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)
820-uut2#sh int 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
Keepalive set (10 sec)
DTR is pulsed for 5 seconds on reset
LCP Closed
Table 4-1 describes possible command output for the show interface command. Each line in the command output example corresponds to a row in this table
| Output | Description |
|---|---|
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Dialer1 is up, line protocol is up Another possible message:Dialer1 is down, line protocol is down |
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Dialer1 is down, line protocol is down
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To display ATM-specific information about an ATM interface, use the show atm interface atm0 privileged EXEC command. Following is the command syntax:
show atm interface atm0
Following is an output example from the show interface atm command:
tw_820#sh atm int atm 0 Interface 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
Table 4-2 describes the fields shown in the command output.
| Field | Description |
|---|---|
ATM interface | Interface number. Always 0 for the Cisco 827 routers. |
AAL enabled | Type of AAL enabled. The Cisco 827 routers support AAL5. |
Maximum VCs | Maximum number of virtual connections this interface supports. |
Current VCCs | Number of active virtual channel connections (VCCs). |
Maximum Transmit | Maximum number of transmit channels. |
Max Datagram Size | The configured maximum number of bytes in the largest datagram. |
PLIM Type | Physical layer interface module (PLIM) type |
This section describes how to use the debug atm commands with additional keywords to troubleshoot the router.
You can use the debug commands to troubleshoot configuration problems that you might be having on your network. Debug commands provide extensive, informative displays to help you interpret any possible problems. All debug commands are entered in privileged EXEC mode, and most debug commands take no arguments. Read the information in Table 4-3 before using debug commands.
 | 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. |
Additional documentation | You can find additional information and documentation about the debug commands in the Debug Command Reference document on the Cisco IOS software documentation CD-ROM that came with your router. If you are not sure where to find this document on the CD-ROM, use the Search function in the Verity Mosaic browser that comes with the CD-ROM. |
Disabling debugging | To turn off any debugging, enter the undebug all command. |
Viewing debug message | To view debug messages on the console, enter the logging console debug command. |
Telnet sessions | If you want to use debug commands during a Telnet session with your router, you must first enter the terminal monitor command. |
Use the debug atm errors command to display ATM errors. The no form of this command disables debugging output. Following is the command syntax:
debug atm errorsFollowing is sample debug atm errors output.
820-uut2#deb atm err ATM errors debugging is on Router# 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
Use the debug atm events command to display ATM events. The no form of this command disables debugging output. Following is the command syntax:
debug atm eventsThis command displays ATM events that occur on the ATM interface processor and is useful for diagnosing problems in an ATM network. It provides an overall picture of the stability of the network.
If the interface is successfully communication 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.
The following output indicates that the ADSL line is up (training successful) and the AAL5 frames are being sent and received.
Router# 01:21:19:c820_vc_tx_start:idb = 0x80CB3AC0, cos_queue = 0x80BBE614 01:21:19:c820_aal_send:pak = 0x80D4BA48, vc = 0d, q = 1c820_aal_send:pak_enctype=0 vcnum=1 enctype=0 01:21:19:pquicc_sar_pak2txring:nextTxBd = 0x80BBE3AC, ring = 0x80F050D0 01:21:19:pquicc_sar_add_pak_tx:packet TX=0x136DC78, len=108, oam?=0 01:21:19:PQUICC_SAR_INTERRUPT:status=800208C0 01:21:19:TX interrupt:conid 2, usedTxBd:Shadow 0x80BBE3AC, Real 0x80CE4F18 01:21:19:pquicc_sar_safe_start:vc = 1 01:21:19:PQUICC_SAR_INTERRUPT:status=800808C0 01:21:19:RX interrupt:conid = 2, rxBd = 0x80CE4540 length=108 01:21:19:process_receive_packet:vcnum=1 enctype=0
If the router has difficulty training, you can see the following:
17:25:02:DSL:SM:[DMTDSL_DLOAD_2 -> DMTDSL_DO_OPEN] 17:25:02:DSL:Send ADSL_OPEN command. 17:25:03:DSL:Using subfunction 0x2 17:25:03:DSL:Sent command 0x3 17:25:06:DSL:1:Modem state = 0x8 17:25:08:DSL:2:Modem state = 0x8 17:25:11:DSL:3:Modem state = 0x8 17:25:13:DSL:4:Modem state = 0x8
Use the debug atm packet command to display per-packet debugging output. The output reports information online when a packet is received or a transmission is attempted. The no form of this command disables debugging output. Following is the command syntax:
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]]
interface atm number | (Optional) ATM interface or subinterface number. |
vcd vcd-number | (Optional) Number of the virtual circuit designator (VCD). |
vc vpi/vci number | (Required) The vpi/vci value of the ATM PVC. |
The debug atm packet command displays all process-level ATM packets for both outbound and inbound packets. This command is useful for determining whether packets are being received and transmitted correctly.
| 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. |
Below is sample debug atm packet output.
Router# 01:23:48:ATM0(O): 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 01:23:48: 01:23:48:ATM0(I): 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 01:23:48:
Table 4-4 describes the fields shown in the debug atm packet command output.
| Field | Description |
|---|---|
ATM0 | Interface that is generating the packet. |
(O) | Output packet. (I) would mean receive packet. |
Pak size | Packet size in bytes. |
VCD: 0xn | Virtual circuit associated with this packet, where n is some value. |
VPI: 0xn | Virtual path identifier for this packet, where n is some value. |
DM: 0xn | Descriptor mode bits, where n is some value. |
MUXETYPE: n | |
Length: n | Total length of the packet (in bytes) including the ATM header(s). |
Following are the methods for upgrading software on the Cisco 827 routers:
This section describes how to recover a lost enable or enable secret password. The process of recovering a password consists of the following major steps:
1. Changing the Configuration Register
3. Resetting the Password and Saving Your Changes (for lost enable secret passwords only)
This section describes how to change a configuration register.
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. Refer to the section "Connecting the Router to a PC" in the "Installation" chapter of the Cisco 827 Routers Hardware Installation Guide.
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 (router_name >), enter the show version command to display the existing configuration register value (shown in bold at the bottom of this output example):
820-uut2#sh ver Cisco Internetwork Operating System Software IOS (tm) C827 Software (C827-NSY6-M), Version 12.0 Copyright (c) 1986-1999 by cisco Systems, Inc. Compiled Mon 22-Nov-99 11:20 by dahsue Image text-base:0x80013170, data-base:0x8081B748 ROM:System Bootstrap, Version 12.0(19990519:174856) [jakumar-twister_dev 1055], DEVELOPMENT SOFTWARE Jay uptime is 48 minutes System returned to ROM by reload Running default software CISCO C827 (MPC855T) processor (revision 0x00) with 19456K/1024K bytes of memory. Processor board ID 00000000, with hardware revision 0000 CPU rev number 5 Bridging software. 4 POTS Ports 1 Ethernet/IEEE 802.3 interface(s) 1 ATM network interface(s) 128K bytes of non-volatile configuration memory. 16384K bytes of processor board System flash (Read/Write) Configuration register is 0x100
Step 4 Record the setting of the configuration register. It is usually 0x2100 or 0x100.
Step 5 Record the break setting:
This section describes how to reset the router.
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.
Step 2 Press break. The terminal displays the following prompt:
rommon 2>
Step 3 Enter confreg 0x142 to reset the configuration register:
rommon 2> confreg 0x142
Step 4 Initialize the router by entering the reset command:
rommon 2> reset
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:
Router>
Step 7 Enter the enable command to enter enable mode. Configuration changes can be made only in enable mode:
Router> enable
The prompt changes to the privileged EXEC prompt:
Router#
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, skip the following "Resetting the Password and Saving Your Changes" section, and complete the password recovery process by performing the steps in the "Resetting 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 "Resetting the Password and Saving Your Changes" section.
This section discusses how to reset your password and save the changes.
Step 1 Enter the configure terminal command to enter 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 configuration mode:
Router(config)# exit
Step 4 Save your configuration changes:
Router# copy running-config startup-config
After you have recovered or reconfigured a password, reset the configuration register value:
Step 1 Enter the configure terminal command to enter 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:
Router(config)# exit
Step 4 Reboot the router, and enter the recovered password.
Posted: Sun Apr 9 17:53:57 PDT 2000
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