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This chapter explains how to isolate problems in the Cisco ICS 7750. It contains the following sections:
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Tips Use this chapter to isolate a problem, then use the remaining chapters and appendices to solve the problem, as follows: |
Use the information in this section to help isolate faults. You can perform these procedures before, after, instead of, or in addition to running the diagnostic software. However, these instructions are the only means of identifying faults in subsystems not covered by a power-on self test (POST) or diagnostics, such as fans and power supply modules.
Some procedures must be performed on site and others can be performed remotely.
This section is organized as follows:
Before running diagnostics or attempting complex troubleshooting, verify the following:
Electrical problems are divided into two categories:
Site electrical problems can include:
System electrical problems can be caused by:
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Note For installation instructions, refer to the Cisco ICS 7750 Hardware Installation Guide. |
The system powers down when the temperature exceeds a specified threshold. If that happens, you should identify and correct the cause of the overheating before reapplying power to the system.
If you are bringing up a node, card, or interface (port) for the first time, a likely source of problems is configuration. The problem may exist at either the local side or the remote side of the connection; be sure to check both configurations.
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Note Refer to the Cisco ICS 7750 Software Configuration Guide for information on configuring nodes, cards, or interfaces. |
Signal input and output problems can occur at any point in the network and can be caused by mechanical defects in the cables, poor connections, or lack of signal caused by other equipment failures.
This section describes how to isolate problems with the following:
Refer to your site log and other facility records to check signal connections for your facility.
You can use the ping command to determine whether you can communicate over a particular IP connection. The ping command sends Internet Control Message Protocol (ICMP) echo packets to the specified IP address and receives a confirmation if the connection is good.
If the console screen connected to the SAP console port appears frozen or fails to work properly, check for the following problems:
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Note For detailed instructions on how to solve problems related to serial connections, see "Solving Serial Connection Problems." |
If an the STATUS LED on the SSP is not on (green), look for the following:
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Caution You can install only one SSP card in a single chassis. If you must hot swap the SSP, the system loses LAN connectivity, and calls being made from or to Cisco IP Phones that are routed through that SSP are disconnected until an operational SSP is properly re-inserted in the chassis. |
If the SSP STATUS LED is on, but one of its Ethernet interfaces does not seem to be working properly, make sure that the interface in question is configured properly and is not administratively shut down. If you have a working console connection, complete the following steps:
Cisco ICS 7750> configure terminal
Enter configuration commands, one per line. End with Ctrl-z.
Cisco ICS 7750(config-if)# int eth slot |interface
Cisco ICS 7750(config-if)# no shut
Cisco ICS 7750(config-if)# exit
Cisco ICS 7750(config)# Ctrl-z
Cisco ICS 7750#
Step 2 Verify that the Ethernet interface has a valid IP address assigned to it.
For more information about configuring Ethernet interfaces, refer to the Cisco ICS 7750 Software Configuration Guide.
If the cable, connections, power, and configuration are normal, and you still cannot connect to the Ethernet interface on the SSP, replace the SSP. If the problem persists, contact Cisco's technical assistance center (TAC) for further assistance.
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Note For instructions on how to solve problems related to Ethernet connections, including a detailed explanation of show interfaces ethernet command output, see "Solving Ethernet Problems." |
This section describes additional sources of information that can help you solve system problems:
System diagnostic commands can provide additional information that can help you solve problems. For more information about diagnostics, see "System Maintenance and Upgrades."
CiscoWorks2000 includes a suite of fault management applications for diagnosing problems on the SNMP devices on your network. These applications include:
Table 4-1 lists CiscoWorks2000 applications that can help you troubleshoot network problems.
| Problem | CiscoWorks2000 Application Recommendation |
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Network device |
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Protocol |
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Device configuration |
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In many situations, third-party diagnostic tools provide the best way to solve difficult problems. For example, invoking a debug command that places heavy demands on system processing power can be disastrous in an environment experiencing excessive traffic. However, attaching a network analyzer to the suspect network is less intrusive and is more likely to yield useful information without interrupting or slowing the operation of the system.
The following are some typical third-party troubleshooting tools:
Volt-ohm meters and digital multimeters are the simplest cable testing tools. These devices measure parameters such as AC and DC voltage, current, resistance, capacitance, and cable continuity. They are used to verify physical connectivity.
Similar testing equipment is available for fiber-optic cable. Fiber-optic cable is expensive and should be tested both before installation (on-the-reel testing) and after installation. Continuity testing of fiber-optic cable requires either a visible light source or an optical time domain reflectometer (OTDR). Light sources capable of providing light at the three predominant wavelengths (850 nm, 1300 nm, and 1550 nm) are used with power meters that can measure the same wavelengths and test attenuation and return loss in the fiber.
A TDR works by bouncing a signal off the end of the cable. Opens, shorts, and other problems reflect the signal back at different amplitudes, depending on the problem. A TDR measures how much time it takes for the signal to reflect and calculates the distance to a fault in the cable. You can also use TDRs to measure the length of a cable, and some TDRs can calculate the propagation rate based on a configured cable length.
Fiber-optic measurement is performed by an OTDR. OTDRs can accurately measure the length of the fiber, locate cable breaks, measure the fiber attenuation, and measure splice or connector losses. You can use an OTDR to take the "signature" of a particular installation, noting attenuation and splice losses. You can then compare this baseline measurement with future signatures when you suspect a problem in the system.
Breakout boxes, fox boxes, bit error rate testers (BERTs), and block error rate testers (BLERTs) are digital interface testing tools used to measure the digital signals present at computers, serial printers, modems, channel service unit/data service units (CSU/DSUs), and other peripheral interfaces. These devices can monitor data line conditions, send, receive, and analyze data, and diagnose problems common to data communication systems. For example, you can examine traffic from data terminal equipment (DTE), such as a computer, through data communications equipment (DCE), such as a modem or CSU/DSU, to help isolate problems, identify bit patterns, and ensure that the proper cabling has been installed. However, you cannot use these devices to test signals passing through Ethernet media.
Network monitors continuously track packets crossing a network providing an accurate picture of network activity at any moment or a historical record of network activity over a period of time. They do not decode the contents of frames. Monitors are useful for sampling network activity over a period of time to establish a normal performance profile, or baseline. Monitors collect information such as packet sizes, the number of packets, error packets, overall usage of a connection, the number of hosts and their Media Access Control (MAC) addresses, and details about communications between hosts and other devices. You can use this data to create profiles of LAN traffic and to assist in locating traffic overloads, planning for network expansion, detecting intruders, establishing baseline performance, and distributing traffic more efficiently.
A network analyzer (also called a protocol analyzer) decodes the various protocol layers in a recorded frame and presents them as readable abbreviations or summaries.
Most network analyzers can perform many of the following functions:
If you cannot resolve your problem using the procedures outlined in this section, collect the following information for your technical support representative:
For more information about these debug commands, refer to the Debug Command Reference.
Posted: Mon Oct 2 13:44:23 PDT 2000
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