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10-13
Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 10 Configuring LRE
Configuring LRE Ports
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:
Table 10-4 SNR Requirements for Upstream Rates
Profile
Gross Data
Rate QAM
Theoretical
Minimum SNR Low Noise SNR
Medium Noise
SNR
High Noise
SNR
LRE-4-1 1.56 4 13 15 17 20
LRE-7 8.333 16 19 21 23 26
LRE-8 9.375 64 25 27 30 34
LRE-5 6.25 4 13 15 17 20
LRE-10 12.5 16 19 21 23 26
LRE-1518.756425273034
LRE-10-5 6.25 4 13 15 17 20
LRE-10-3 3.125 16 19 21 23 26
LRE-10-1 1.56 4 13 15 17 20
LRE-15-5 6.250 4 13 15 17 20
LRE-15-33.1251619212326
LRE-15-1 1.563 4 13 15 17 20
LRE-998-15-4 4.688 64 25 27 29 32
LRE-997-10-4 4.688 64 25 27 29 32
LRE-2 2.08 4 13 15 17 20
LRE-3 3.13 4 13 15 17 20
LRE-4 4.17 4 13 15 17 20
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface LRE-interface Enter interface configuration mode, and enter the number of the
LRE port to be configured.
Step 3
margin [downstream value | upstream value] Enter the downstream or upstream margin value (in dB)
Step 4
end Return to privileged EXEC mode.
Step 5
show controllers lre profile details Verify the change.