ADSL Troubleshooting

Author: James Saunders Date: Tue, 8 May 2007 20:58:00 CEST

1. Check if the CD (Carrier Detect) light is lit on the router or the wic card

If the CD is not lit, this suggests a cable, filter or line issue.
Swap the cable and filter and see if the CD light comes on.

2. Confirm the the ADSL interface is seen, using "show version" and "show diag"

Some IOS versions do not support ADSL ports or if the card has failed it may not be visible to the router:

router#sh ver
...
1 FastEthernet/IEEE 802.3 interface(s)
1 ISDN Basic Rate interface(s)
1 ATM network interface(s)
1 Virtual Private Network (VPN) Module(s)

router#sh diag
...
     WIC Slot 1:
        Alcatel 20150 ADSL WIC WAN daughter card-Version 4 TLV Cookie Format
        Hardware Revision        : 2.3
        Part Number              : 73-4771-09
        Board Revision           : C0
        Deviation Number         : 0-0
        Fab Version              : 05
        PCB Serial Number        : FOC08490WEZ
        RMA Test History         : 00
        RMA Number               : 0-0-0-0
        RMA History              : 00
        Product (FRU) Number     : WIC-1ADSL=

3. Is the line training?

An ADSL connection needs to syncronise with a piece of kit called a DSLAM at the exchange.

You can see this occuring on the router using the "debug atm events" Command, then disconnect the ADSL line and plug it back in.

Good Debug:

*Aug 23 21:00:51.112: DSL(ATM0) : Defect: LOM
*Aug 23 21:00:51.112: DSL(ATM0): Defect: LOS LOF LCDf: retraining
*Aug 23 21:00:51.112: DSL(ATM0): Received response: 0x41
*Aug 23 21:00:53.616: DSL(ATM0): Send ADSL_CLOSE command.
*Aug 23 21:00:53.616: DSL(ATM0): Sent command 0x4
*Aug 23 21:00:54.140: DSL(ATM0): Received response: 0x25
*Aug 23 21:00:54.140: DSL(ATM0): Connection closed
*Aug 23 21:00:54.148: DSL(ATM0): Send ADSL_OPEN command.
*Aug 23 21:00:54.148: DSL(ATM0): Using subfunction 0x15
*Aug 23 21:00:54.148: DSL(ATM0): Sent command 0x3
*Aug 23 21:00:56.648: DSL(ATM0): 1: Modem state = 0x8
*Aug 23 21:00:59.148: DSL(ATM0): 2: Modem state = 0x8
*Aug 23 21:01:01.648: DSL(ATM0): 3: Modem state = 0x8
*Aug 23 21:01:04.148: DSL(ATM0): 4: Modem state = 0x8
*Aug 23 21:01:06.648: DSL(ATM0): 5: Modem state = 0x10
*Aug 23 21:01:09.148: DSL(ATM0): 6: Modem state = 0x10
*Aug 23 21:01:11.648: DSL(ATM0): 7: Modem state = 0x10
*Aug 23 21:01:14.148: DSL(ATM0): 8: Modem state = 0x10
*Aug 23 21:01:15.004: DSL(ATM0): Received response: 0x24
*Aug 23 21:01:15.004: DSL(ATM0): Showtime!

Bad Debug:

*Aug 23 21:00:51.112: DSL(ATM0) : Defect: LOM
*Aug 23 21:00:51.112: DSL(ATM0): Defect: LOS LOF LCDf: retraining
*Aug 23 21:00:51.112: DSL(ATM0): Received response: 0x41
*Aug 23 21:00:53.616: DSL(ATM0): Send ADSL_CLOSE command.
*Aug 23 21:00:53.616: DSL(ATM0): Sent command 0x4
*Aug 23 21:00:54.140: DSL(ATM0): Received response: 0x25
*Aug 23 21:00:54.140: DSL(ATM0): Connection closed
*Aug 23 21:00:54.148: DSL(ATM0): Send ADSL_OPEN command.
*Aug 23 21:00:54.148: DSL(ATM0): Using subfunction 0x15
*Aug 23 21:00:54.148: DSL(ATM0): Sent command 0x3
*Aug 23 21:00:56.648: DSL(ATM0): 1: Modem state = 0x8
*Aug 23 21:00:59.148: DSL(ATM0): 2: Modem state = 0x8
*Aug 23 21:01:01.648: DSL(ATM0): 3: Modem state = 0x8
*Aug 23 21:01:04.148: DSL(ATM0): 4: Modem state = 0x8
*Aug 23 21:01:06.648: DSL(ATM0): 5: Modem state = 0x8
*Aug 23 21:01:09.148: DSL(ATM0): 6: Modem state = 0x8
*Aug 23 21:01:11.648: DSL(ATM0): 7: Modem state = 0x8
*Aug 23 21:01:14.148: DSL(ATM0): 8: Modem state = 0x8

If the modem state stays at 0x8 this says there is a fault between the router and exchange, reloace the cable and the filter, retest if you still have an error then it is a line issue.

4. Confirm if you have an IP

Most ADSL line installations will use a dialer interface to dial out, this interface will normally be given an IP address on connection, so check if your dialer has an IP and the configuration method is IPCP.

If it has an IP then there is not issue with the line, filter, cable, card or router.

If is the wrong IP then it is likely to be an incorrect username and password.

router#sh ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
Dialer1                    217.34.5.190    YES IPCP   up                    up      
ATM0                       unassigned      YES NVRAM  up                    up   

5. You have a CD light

If you have a CD light and you can see the line retraining and still do not receive an IP address for your dialer interface then it may be an authentication fault. Confirm the ADSL username and password with the ISP (normally both are case sensitive) you can also reconfigure the router with the BT test account, this will prove that the line is good:

• Username: bt_test@startup_domain
• Password: 123

OR (note: this one only works on some lines, depends on service provided)

• Username: speedtest@speedtest_domain
• Password: **blank**

If you use the speed test login, you may be able to access the following BT websites (Depends on your router config):

• http://217.35.209.142 or http://217.32.105.42

e.g.

interface Dialer1
 ppp chap hostname bt_test@startup_domain
 ppp chap password 123
 ppp pap sent-username bt_test@startup_domain password 123

router#sh ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
Dialer1                    217.32.29.166   YES IPCP   up                    up      
                           ^^^^^^^^^^^^^
                         BT Test IP address