Cisco 2950G 24 Software Configuration Guide - Page 261

Chapter 10 Configuring LRE Configuring LRE Ports Table 10-4 SNR Requirements for Upstream Rates Profile LRE-4-1 LRE-7 LRE-8 LRE-5 LRE-10 LRE-15 LRE-10-5 LRE-10-3 LRE-10-1 LRE-15-5 LRE-15-3 LRE-15-1 LRE-998-15-4 LRE-997-10-4 LRE-2 LRE-3 LRE-4 Gross Data Rate 1.56 8.333 9.375 6.25 12.5 18.75 6.25 3.125 1.56 6.250 3.125 1.563 4.688 4.688 2.08 3.13 4.17 QAM 4 16 64 4 16 64 4 16 4 4 16 4 64 64 4 4 4 Theoretical Minimum SNR 13 19 25 13 19 25 13 19 13 13 19 13 25 25 13 13 13 Medium Noise Low Noise SNR SNR 15 17 21 23 27 30 15 17 21 23 27 30 15 17 21 23 15 17 15 17 21 23 15 17 27 29 27 29 15 17 15 17 15 17 High Noise SNR 20 26 34 20 26 34 20 26 20 20 26 20 32 32 20 20 20 The margin range for link qualification is from 1 to 10 dB. The recommended value in a low-noise environment is 2 dB. The recommended value for medium noise environment is 4 dB. The recommended value in a high noise environment is 6 dB. If a profile has a theoretical minimum of 25 dB and you configure a margin of 3 dB, when the link is established, the SNR should at the least be 28 dB to indicate a successful link. If a link is established and if the SNR value at link time is 27 dB, the link is advertised as down, and the next profile in the sequence is attempted. If you configure a margin of 0 (the default value), IOS does not check for the SNR value when the link is established. Beginning in privileged EXEC mode, follow these steps to assign a margin to a specific LRE port: Step 1 Step 2 Step 3 Step 4 Step 5 Command Purpose configure terminal Enter global configuration mode. interface LRE-interface Enter interface configuration mode, and enter the number of the LRE port to be configured. margin [downstream value | upstream value] Enter the downstream or upstream margin value (in dB) end Return to privileged EXEC mode. show controllers lre profile details Verify the change. 78-14982-01 Catalyst 2950 Desktop Switch Software Configuration Guide 10-13