Chapter 4 Connecting the Cisco uBR7225VXR Router to the Cable Headend
Measuring the Upstream RF Signal
Step 10 Verify that your headend RF measurements meet the recommended DOCSIS parameters listed in the tables in Appendix B, “RF Specifications.”
Step 11 Record your headend settings in Appendix G, “Site Log.” This will assist in troubleshooting the Cisco uBR7225VXR universal broadband router installation later in the process.
Note Be sure not to narrow the focus of your analysis any further than approximately
Analyzing the Upstream RF Signal
When you have set up your spectrum analyzer to accurately read the upstream RF signal, you can verify that a remote cable modem is operating as it should by pinging the modem via a console terminal.
Step 1 Log in to your Cisco uBR7225VXR universal broadband router with a console terminal.
Step 2 Adjust the sweep time on your spectrum analyzer to 20 microseconds.
Step 3 Ping the remote cable interface card using first a
Figure 4-29 and Figure 4-30 provide two examples of an ideal upstream RF signal based on a simple 64- or 1500-byte ping of a single remote cable interface. The more slender of the data spikes in the RF signal (the first and third spikes in Figure 4-29) are bandwidth request packet transmissions, while the larger spikes are the actual 64- or 1500-byte ping packet returns.
Figure 4-29 Analyzing the Upstream RF Signal—64-Byte Data Packets
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