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Table Of Contents
Troubleshooting the Installation
Problem Solving with Subsystems
Identifying Installation Problems
Troubleshooting the Power Subsystem Using LEDs
Troubleshooting the Coaxial Cable
Troubleshooting the RF and Digital Signals
Troubleshooting the Personal Computer
Troubleshooting the Installation
Every Cisco uBR904 cable modem goes through extensive testing before leaving the factory. However, if you encounter a problem starting the cable modem, use the information in this chapter to help isolate the cause of the problems. This chapter contains the following sections:
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Troubleshooting the Power Subsystem Using LEDs
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The procedures in this chapter assume that you are troubleshooting an initial cable modem installation, that the HFC network to the installation site is active, that a cable headend technician familiar with the Cisco uBR7246 universal broadband router has been consulted to investigate the possibility of a problem at the headend, and that the Cisco uBR904 cable modem is in the original factory configuration. If you have removed or replaced components or changed any default settings, the recommendations in this chapter might not apply.
If you are unable to easily solve the problem, after consulting with the cable headend technician, contact a customer service representative for assistance and further instructions. Provide the representative with the following information:
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Figure 5-1 shows the general troubleshooting strategy described in this chapter. Refer to this chart, as necessary, to follow the steps to isolate problems to a specific subsystem; then resolve the problem if possible.
Figure 5-1 Troubleshooting Strategy for Startup Problems
Troubleshooting Overview
This section describes the troubleshooting methods used in this chapter and describes how the Cisco uBR904 cable modem is divided into subsystems for more efficient problem solving.
Problem Solving with Subsystems
The key to solving problems with the system is isolating the problem to a specific subsystem. The first step in solving startup problems is to compare what the system is doing to what it should be doing. Because an installation problem is usually caused by a single component, it is more efficient to first isolate the problem to a subsystem rather than troubleshoot each component in the system. For these troubleshooting procedures, consider the following subsystems:
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The following sections will help you isolate a problem to one of these subsystems and direct you to the appropriate troubleshooting section.
Identifying Installation Problems
Installation problems with a Cisco uBR904 cable modem are commonly due to the HFC network and its topography.
When you start up the Cisco uBR904 cable modem for the first time, you should observe the power-up sequence described in the section "Starting the Cisco uBR904 Cable Modem" in the chapter "."
LEDs indicate cable modem operational states in the startup sequence. For a detailed description of the LEDs, see the section, "Troubleshooting the Power Subsystem Using LEDs," for details. By checking the state of the LEDs, you can determine when and where the system failed in the startup sequence. Use the following descriptions to isolate the problem to a subsystem, then proceed to the appropriate sections to try to resolve the problem.
When you start up the cable modem by plugging one end of its power cord to the power supply and the other end of the power cord to a grounded AC-input power outlet, the following should occur:
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If the LED does not start to blink, proceed to the section "Troubleshooting the Power Subsystem Using LEDs."
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Troubleshooting the Power Subsystem Using LEDs
Check the following to help isolate a problem with the cable modem power subsystem:
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Figure 5-2 Cisco uBR904 Front Panel LEDs
See for descriptions of the LEDs.
Using the Reset Switch
You can reset and reboot your Cisco uBR904 using a cold or warm reset as described in .
Troubleshooting the Coaxial Cable
The cable modem will not function if the connection from the Cisco uBR904 cable modem to the Cisco uBR7246 universal broadband router is not established because the cable modem is configured from the cable headend. There are many conditions inherent to coaxial cable that can inhibit this connection:
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If the center conductor is not straight or appears to be too long or too short, cut the coaxial cable behind the connector end, and strip the insulation back. Make sure that the newly exposed center conductor is straight. Before replacing the new cable connector end, check the general condition of the cable. Make sure the new conductor end is securely crimped to the cable.
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The coaxial cable between the cable modem and the cable tap must be very high quality. The cable insulation must be at least 80% braid with foil. If the existing cable appears to be of lesser quality or in poor condition, replace the cable from the ground block or tap to the cable end.
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Check that the coaxial cable end is securely screwed onto the F-connector at the back of the cable modem.
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Troubleshooting the RF and Digital Signals
The use of RF and digital signals on the same cable can lead to interference if the HFC network is not correctly configured.
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Connect a premium services cable converter to the ground block or at the tap and contact your customer service department. Ask a customer service representative at your main office to check if they can locate the box on the network by sending an impulse, or on-demand, video signal to the converter.
If customer service can locate the converter at the ground block or at the tap, repeat the test with cable modem connected to the cable end near the computer.
If customer service cannot locate the converter at the cable end, but can locate the converter at the ground block or tap, replace the cable from the ground block or tap to the cable end.
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Depending on how the Cisco uBR7246 universal broadband router was set up at the cable headend, the digital data signal will be 6 or 10 dB below the amplitude of the next adjacent video signal. You should always know this value before attempting an installation. Confirm this value with a headend technician.
Use a portable field strength meter, or power meter, to measure the adjacent analog video signal:
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Measure the digital data signal. It should be 6 or 10 dB (based on the settings at the headend) below the video signal measured above.
If you are unable to resolve the problem, contact your internal service organization for instructions and assistance.
Troubleshooting the Personal Computer
Check the following to help isolate a problem with the personal computer that is connected to the cable modem:
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If you cannot access a Web page, verify that the computer network protocol is configured for IP and DHCP services are enabled using the following Windows 95 options:
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Make sure that the box next to Obtain IP Address Automatically is selected. If this box is not selected, the computer is not configured for DHCP. Select the Obtain IP Address Automatically box now and save your configuration settings.(f)
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If you need additional information, refer to the user guides or other documentation that accompanied the computer. Contact technical support for the computer manufacturer as necessary.
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Verify that the network card is installed properly and that necessary software drivers have been installed and are running on the computer. Consult the user guide or other documentation that accompanied the network card. Contact technical support for the network card manufacturer as necessary.
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