Cisco 1721 - Manual (Page 57)

3-7
Cisco 1721 Router Hardware Installation Guide
78-13834-02
Chapter 3 Troubleshooting
Problem Solving
Step 3 Press Ctrl-Z to exit configuration mode:
Router(config)# Ctrl-Z
Step 4 Reboot the router, and enter the recovered enable password.
Problem Solving
The key to problem solving is to isolate the problem to a specific subsystem by
comparing what the router is doing to what it should be doing.
In problem solving, consider the following subsystems of the router:
• WICs—Refer to the LEDs on the cards and the LEDs on the router front panel
to help identify a failure. For more information on WICs, refer to the
Cisco WAN Interface Cards Hardware Installation Guide, which comes with
each card.
• Cables—Check all the external cables that connect the router to the network.
• Power system—Check the external power source, power cable, router power
supply, and circuit breaker. Check for inadequate ventilation or air circulation
that might cause overheating.
• ISDN configuration—Consider ISDN-specific hardware and software
configurations (ISDN BRI WICs only).
OK LED Diagnostics
Use the front-panel OK LED to determine any problems with the router. When the
router first boots up, it performs a power-on self-test (POST). If the router detects
a problem during the POST, the OK LED blinks in different patterns (described
in
Table 3-1 ), depending on the problem. A pattern consists of a specific number
of blinks that is repeated until the router is turned off. If the router experiences
any of these problems, contact your Cisco reseller.