Chapter 6 Troubleshooting
Verifying the Downstream Signal
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: http://www.cisco.com/en/US/support/index.html
•Search cable products field notices at the following URL: http://www.cisco.com/en/US/support/tsd_products_field_notice_summary.html
•Find router and Cisco IOS architecture technical tips at the following URL: http://www.cisco.com/en/US/products/hw/routers/ps341/prod_tech_notes_list.html
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
Tip A maximized
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 on page
•Set up the console. See the Cisco uBR7200 Series Software Configuration Guide at the following URL:
http://www.cisco.com/en/US/docs/cable/cmts/ubr7200/configuration/guide/cr72scg.html
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
•
•Downstream signal frequency
•Downstream signal modulation scheme (64 QAM or 256 QAM) Example:
Router# show controllers cable-modem 0
Tuner:status=0x00
Rx:tuner_freq 555000000, symbol_rate 5055926, local_freq 11520000
Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
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