This chapter provides troubleshooting information for the Cisco uBR7225VXR universal broadband router and contains the following sections:
•Problem Solving with Subsystems
•Verifying the Downstream Signal
This chapter contains instructions to help installers and technicians troubleshoot hardware installation.
Figure 6-1 shows the general troubleshooting strategy used to troubleshoot the hardware. Refer to this flow chart as necessary and follow the steps to isolate hardware problems to a specific subsystem.
For cable-specific commands for the Cisco uBR7225VXR universal broadband router, refer to the Cisco IOS CMTS Cable Command Reference Guide at the following URL:
Resolve the problem if possible or contact the Cisco Technical Assistance Center.
If you are contacting Cisco TAC or your customer service representative, provide the following information:
•Date you received your Cisco uBR7225VXR universal broadband router
•Chassis serial number
•Type of software and release number
•Brief description of the problem you are having
•Brief explanation of the steps you have taken to isolate and resolve the problem
•Maintenance agreement or warranty information
Figure 6-1 Troubleshooting Strategy for Startup Problems
Problem Solving with Subsystems
Tip Isolating a problem to a specific subsystem simplifies the troubleshooting process.
The first step in isolating a problem is to compare what the system is doing to what it should be doing. Usually a startup problem is caused by a single component, so first isolating the problem to a subsystem rather than troubleshooting every component in the entire system is more efficient. The Cisco uBR7225VXR router subsystems are listed below.
•Power subsystem—Includes the power supplies, the external power cable, and the midplane.
•Cooling subsystem—The chassis fan tray is the single component in this subsystem. The fans should be operating whenever system power is on.
•Processor subsystem—Includes the network processing engine and cable interface line cards.
The system memory and management functions reside on the network processing engine. The enabled LED on each cable interface line card indicates if the cable interface line card is initialized.
A cable interface line card that is partially installed in the midplane can the cause system to hang and crash.
•Cable headend subsystem—External to the Cisco uBR7225VXR router, this subsystem can prevent operation of the universal broadband router if the headend is not properly set up for the introduction of digital data into the hybrid fiber-coaxial (HFC) network.
The following section helps you isolate a problem to one of the subsystems and directs you to the appropriate troubleshooting section.
Identifying Startup Problems
When you start up the Cisco uBR7225VXR router for the first time, observe the startup sequence described in the "Powering On the Cisco uBR7225VXR Router" section. This section contains a detailed description of the normal startup sequence.
Although an overtemperature condition is unlikely at initial startup, the environmental monitoring functions are included in this chapter because they also monitor internal voltages.
Startup problems are commonly caused by source power problems or a board (network processing engine or cable interface line card) that is not properly connected to the midplane. Always check that your boards are properly installed in the chassis.
With the exception of the fan tray and network processing engine, LEDs indicate all system states in the startup sequence. By checking the state of the LEDs, you can determine when and where the system failed in the startup sequence.
Note On rare occasions, an LED may be faulty.
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 system, by turning on the power supply switch, the following should occur:
1. You should immediately hear the fans operating. If not, proceed to the "Cooling Subsystem" section. If you determine that the power supply is functioning normally and that a fan is faulty, contact a customer service representative. If a fan does not function properly at initial startup, there are no installation adjustments that you should make.
2. The power supply's green Input OK LED (at the rear of the chassis) should go on immediately when you place the power supply switch in the ON (|) position, and should remain on during normal system operation. If the green Input OK LED does not go on, proceed to the "Power Subsystem" section.
3. The enabled LED on each cable interface line card comes on when the network processing engine completes its initialization of the card for operation. The enabled LED indicates that the line card is receiving power and has been recognized by the network processing engine; it does not indicate the state of the individual interfaces on the card. If an enabled LED fails to come on, refer to the "Troubleshooting Cable Interface Line Cards" section.
4. When all LEDs come on to indicate that the system has booted successfully, the initial system banner should appear on the console screen. If it is not displayed, refer to the "Console and Auxiliary Port Connection Equipment" section to verify that the terminal is set correctly and that it is properly connected to the console port on the NPE.
Check the following to help isolate a problem with the power subsystem:
Step 1 Toggle the power supply switch off and on.
Step 2 On the first power supply, is the Input OK LED on?
a. If yes, the power source is good, and the power supply is functional.
b. If not, make sure that the power cable is connected at both ends. Then toggle the power switch off and on.
Step 3 If the Input OK LED remains off, and the power switch is on, suspect the power source or the power cable.
a. Turn the switch off, and connect the power cable to another power source, if available.
b. Turn the switch back on.
c. If the Input OK LED comes on, the problem is the first power source.
Step 4 If the Input OK LED fails to come on after you connect the power supply to a new power source,
a. Turn the power switch off.
b. Replace the power cord.
c. Turn the switch back on.
Step 5 If the Input OK LED comes on, return the first power cable for replacement. Contact a service representative for further instructions.
Step 6 If the Input OK LED still fails to come on when the power supply is connected to a different power source with a new power cable, the power supply is probably faulty.
a. If a second power supply is available, and your Cisco uBR7225VXR router has a redundant power supply bay, install the second power supply in the second bay if there is no power supply installed in that bay.
b. Contact a service representative for further instructions.
Step 7 Is the Input OK LED on for the second (redundant) power supply?
a. If yes, proceed to the "Cooling Subsystem" section.
b. If not, repeat each of the above procedures for the second power supply.
Step 8 If you are unable to resolve the problem or if you determine that either a power supply or chassis connector is faulty, contact a service representative for instructions.
Check the following to help isolate a problem with the cooling system:
Step 1 Verify that the fans are operating when you start up the system.
To determine if the fans are operating, listen for them. In noisy environments, place your hand on the left side of the chassis (when viewing the chassis from the front) to feel for air being forced out the vents.
a. If yes, the power to the fan tray is good.
b. If no, there is a problem with the fan tray or power. See the "Power Subsystem" section.
Step 2 Verify that the following message is not displayed.
%ENVM-1-SHUTDOWN: Environmental Monitor initiated shutdown
If the message is displayed, the system has detected an overtemperature condition or power out-of-tolerance condition inside the chassis.
The shutdown message could also indicate a faulty component or temperature sensor. Before the system shuts down, use the show environment or show environment table command to display the internal chassis environment.
If an environmental shutdown results from a power out-of-tolerance condition, the power OK LEDs goes off and the system shuts down. See the "Power Subsystem" section.
Step 3 Although an overtemperature condition is unlikely at initial startup, ensure that heated exhaust air from other equipment is not entering the inlet vent on the router and that there is sufficient clearance around the sides of the chassis to allow cooling air to flow. Refer to the "Site Environment" section and the "Equipment Racks" section for more on site configurations.
The processor subsystem is comprised of the network processing engine and all cable interface cards. The network processing engine is a required system component. The system cannot operate unless the network processing engine is installed properly; however, the system can operate without any cable interface card installed.
Note The network processing engine (NPE-G1 or NPE-G2) used in Cisco uBR7225VXR allows the router to work without an I/O controller. NPE-G1 and NPE-G2 works with both Cisco uBR7225 and Cisco uBR7246 chassis.
If a cable interface card is partially connected to the midplane, the card sends connection incomplete signals to the processor, which then faults the peripheral component interconnect (PCI) bus and causes the system to hang.
Therefore, first ensure that the network processing engine is installed properly and the system software has initialized successfully. Then, if necessary, you can troubleshoot individual cable interface cards.
Troubleshooting the Network Processing Engine
Check the following to help isolate a problem with the network processing engine (NPE):
Step 1 If the NPE enabled LED does not go on as expected:
a. Turn off the power to the router.
b. Reseat the network processing engine in its slot.
c. Restart the router.
Step 2 Verify that you are running a version of Cisco IOS software that supports the NPE you are using:
a. For the latest Cisco IOS software release information, refer to the Cisco uBR7200 series release notes at the following URL:
b. Use the show version command to determine the NPE that is installed in your router.
c. If the router does not respond to the console input, contact Cisco TAC for instructions.
Step 3 If the enabled LED remains off, the system detected a processor hardware failure. This LED should be on in normal operation. Contact Cisco TAC for instructions.
Troubleshooting Cable Interface Line Cards
Check the following to help isolate a problem with the cable interface line cards:
Step 1 Verify that all cable interface card enabled LEDs are on. If yes, the system is operational.
Step 2 Check to see if all cable interface line card enabled LEDs are off.
a. If yes, verify that you are running a version of Cisco IOS software that supports the cable interface line cards you are using.
For the latest Cisco IOS software release information, refer to the Cisco uBR7200 series release notes, at the following URL:
For the latest information on supported features, refer to the Cisco uBR7200 series software feature guides at the following URL:
b. If the Cisco IOS software is correct, contact Cisco TAC for instructions.
Step 3 Check to see if any cable interface line card enabled LEDs are off.
a. If the enabled LED on an individual cable interface line card is off, check to see if the cable interface line card has pulled away from the midplane.
b. Reseat the cable interface line card in its slot. (You do not have to turn off the system power when removing or replacing cable interface line cards.)
c. After the system reinitializes the interfaces, the enabled LED on the cable interface line card should come on.
Step 4 If the enabled LED remains off, the system detected a processor hardware failure. This LED should be on in normal operation. Contact Cisco TAC for instructions.
Other Troubleshooting Information Websites
These websites are provided to help you find the most current troubleshooting information:
•Search the Cisco TAC assistance website, at the following URL:
•Search cable products field notices at the following URL:
•Find router and Cisco IOS architecture technical tips at the following URL:
Verifying the Downstream Signal
If the Cable Modem Termination System (CMTS) has not been properly set up to support digital data, the Cisco uBR7225VXR router might start up, but fail to support data transmission. You can use a router with diagnostic capabilities, such as the Cisco uBR900 series cable access routers, to verify the downstream signal originating from a Cisco uBR7225VXR router. The Cisco uBR900 series cable access routers are equipped with 64- and 256-QAM receivers that require only minimal setup. Configure the Cisco uBR900 series routers according to DOCSIS practices.
Tip A maximized signal-to-noise ratio (SNR) estimate optimizes cable interface reliability and service quality.
Note The SNR estimate for a cable interface installed at the headend should be between 35 and 39 dB.
Before starting this procedure:
•Connect the Cisco uBR7225VXR router to the console. See the "Console and Auxiliary Port Connection Equipment" section.
•Set up the console. See the Cisco uBR7200 Series Software Configuration Guide at the following URL:
To verify the downstream signal originating from the Cisco uBR7225VXR router:
Step 1 When the Cisco uBR900 series cable access router is operating and you have established an input signal of between -10 and +10 dBmV on the modem, enter the show controllers cable-modem 0 command. This command displays:
•Signal-to-noise ratio (SNR)
•Downstream signal frequency
•Downstream signal modulation scheme (64 QAM or 256 QAM)
Router# show controllers cable-modem 0
Rx:tuner_freq 555000000, symbol_rate 5055926, local_freq 11520000
snr_estimate 352(TenthdB), ber_estimate 0, lock_threshold 26000
QAM in lock, FEC in lock, qam_mode QAM_64
This shows a downstream frequency of 555 MHz, 64-QAM downstream, and an SNR estimate of 35.2 dB.
Note Use the debug cable mac log verbose and show controllers cable 0 mac state commands when troubleshooting the cable interface's initialization sequence and locking on the downstream signal.
Step 2 Scan the output for the value corresponding to the "SNR_estimate" variable. If this value is at least 35 dB, then you have an optimized signal. If the value is less than 34 dB, you must adjust the cable interface line card.
a. Verify that the line card DS output level is correct (+32 dBmV or +42 dBmV).
b. Make sure that the Cisco uBR7225VXR line card IF input to the upconverter is within an acceptable range (check the upconverter manufacturer's specifications).
c. Check the upconverter RF output level. A typical setting is +55 to +58 dBmV.
d. Make sure that the upconverter RF output center frequency has been set correctly.
e. Make sure that the proper amount of attenuation has been installed between the upconverter RF output and the headend combiner input so that the digitally modulated carrier's average power level is 6 dB to 10 dB below the level of the analog TV channels.
f. Make sure that the digitally modulated carrier's RF average power level is in the -15 dBmV to +15 dBmV range at the input to the cable router.
Note The exact value displayed will vary from cable interface to cable interface; however, the values collected from measurement to measurement on the same router will be consistent.
Step 3 If the previous steps do not identify the problem, check the downstream digitally modulated carrier using a QAM analyzer. Several third-party test equipment manufacturers have these instruments available.
a. Measure modulation error ratio (MER), which should be 35 dB or greater in the headend.
b. Check pre- and post-FEC bit error rate (BER). There should be no bit errors in the headend. If bit errors are observed, one likely cause is sweep transmitter interference.
–Check the sweep transmitter to make sure that adequate guard bands have been programmed around the digitally modulated carrier.
–Bit errors also may be caused by clipping of the digitally modulated carrier in the upconverter or other active device, including amplifiers and optical transmitters.
c. Evaluate the digitally modulated carrier's constellation. Look for evidence of:
–Inphase and quadrature (I-Q) imbalance