Cisco Systems uBR7200 Series Anleitung zur Fehlerbehebung PDF herunterladen (Seite 36)

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Cisco uBR7200 Series Universal Broadband Router Software Configuration Guide

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Chapter 4 Troubleshooting the System

Troubleshooting Using Cable Flap Lists

Tips In Cisco IOS Release 12.0(7)XR2, Cisco IOS Release 12.1(1a)T1, and higher, the system

supports automatic power adjustments. The show cable flap-list and show cable modem

commands now indicate when the Cisco uBR7200 series router has detected an unstable

return path for a particular modem and has compensated with a power adjustment. An

asterisk appears in the power adjustment field for a modem when a power adjustment has

been made; an exclamation point appears when the modem has reached its maximum

power transmit level and cannot increase its power level any further.

The following tips and scenarios allow you to use the flap list in the most effective way:

• If a subscriber's cable modem shows a lot of flap list activity, it is having communication problems.

• If a subscriber's cable modem shows little or no flap list activity, it is communicating reliably; the

problem is probably in the subscriber's computer equipment or in the connection to the

cable modem.

• The top 10% most active cable modems in the flap list are most likely to have difficulties

communicating with the headend.

• Cable modems with more than 50 power adjustments per day have a suspect upstream path.

• Cable modems with approximately the same number of hits and misses and with a lot of insertions

have a suspect downstream path (for example, low level into the cable modem).

• All cable modems incrementing the insertion at the same time indicates a provisioning server

failure.

• Cable modems with high CRC errors have bad upstream paths or in-home wiring problems.

• Correlating cable modems on the same physical upstream port with similar flap list statistics can

quickly resolve outside plant problems to a particular node or geography.

• Monitoring the flap list cannot affect cable modem communications.

• The flap list should be saved to a database computer and cleared at least once a day.

• Important upstream performance data can be obtained by tracking flap list trend data.

• Important installation quality control and performance data is directly available from the flap list.

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Cisco Systems uBR7200 Series Anleitung zur Fehlerbehebung Seite 36