Troubleshooting Basics

Troubleshooting provides information on how to diagnose general operational issues for the Cisco 627 asymmetric digital subscriber line (ADSL) Discrete Multi-Tone (DMT) modem. There are some known issues described in this chapter as well as their solutions.

5.1 WAN LNK LED

If the WAN-LNK LED does not appear "on" when you power up the modem, wait for about 15 seconds. If the LED does not light up after 15 seconds, double-check all cabling and connections. If the LED still does not light up, turn the power off and then on again. If the LED still does not light up, call your service representative. Should the PWR/ALARM LED appear RED, turn the power off and then on again. If the LED still appears RED, call your service representative.

5.1.1 Reasons Why the WAN LNK LED Turns Off

1. If the WAN LNK LED blinks continuously and never stays on continuously, the Cisco 627 never trains with the Cisco 6100 or Cisco 6200 series digital subscriber line access multiplexer (DSLAM). There are a number of reasons why this might occur:

The ADSL line is not connected to the Cisco 627.
There are no available ATU-Cs with which the Cisco 627 can train up.
The ADSL circuit is too long.
There is excessive noise on the ADSL circuit.

2. If the WAN LNK LED turns off after the Cisco 627 has successfully been transferring data end-to-end for some time, this means that the Cisco 6100 or 6200 series DSLAM may have the SESSION timeout set, which affects the WAN LNK LED:

SESSION timeout: This timeout can be set on the Cisco 6100 or 6200 series DSLAM. If the SESSION timeout is set to some value, then the Cisco 627 WAN LNK LED will turn off after that certain period of set time whether it is idle or not.

5.2 Serial Buffer Overflow

When using the serial port as your terminal connection, large amounts of serial data may overflow the serial buffer. This results in unintelligible ASCII appearing on the screen but does not affect performance or operation in any way. To avoid this, use Telnet to manage the Cisco 627.

5.3 Running Linux Without term/termcap

Computers running Linux without the "term"/"termcap" database installed will have trouble connecting to Cisco equipment. The message "BAD ADDRESS" is sometimes displayed as an error message. The user can install the term/termcap database from the Linux install disks or CD-ROM.

5.4 Clearing PC Cache with ARP

If you are using a Windows 95 PC to update IP addresses on many Cisco 627s in rapid succession, the PC's ARP cache may not clear right away. This causes communications problems with the subsequent Cisco 627s in the line. To clear the PC cache, use the following command at the MS-DOS prompt on your PC:

c:\> arp -d 192.168.0.100

This deletes the MAC address and causes IP to ARP again at IP address 192.168.0.100. The ARP utility comes with Windows 95 and Windows NT. You can install it from your original Windows 95 or Windows NT install disks or CD-ROM if it isn't in your current installation.

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