Cisco 2950G 24 - Catalyst Switch Software Configuration Manual page 261

Chapter 10 Configuring LRE
Table 10-4 SNR Requirements for Upstream Rates
Gross Data
Profile Rate
LRE-4-1 1.56
LRE-7 8.333
LRE-8 9.375
LRE-5 6.25
LRE-10 12.5
LRE-15 18.75
LRE-10-5 6.25
LRE-10-3 3.125
LRE-10-1 1.56
LRE-15-5 6.250
LRE-15-3 3.125
LRE-15-1 1.563
LRE-998-15-4 4.688
LRE-997-10-4 4.688
LRE-2 2.08
LRE-3 3.13
LRE-4 4.17
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:
Command
Step 1
configure terminal
Step 2
interface LRE-interface
Step 3 margin [downstream value | upstream value] Enter the downstream or upstream margin value (in dB)
Step 4
end
Step 5
show controllers lre profile details
78-14982-01
Theoretical
QAM Minimum SNR
4 13
16 19
64 25
4 13
16 19
64 25
4 13
16 19
4 13
4 13
16 19
4 13
64 25
64 25
4 13
4 13
4 13
Purpose
Enter global configuration mode.
Enter interface configuration mode, and enter the number of the
LRE port to be configured.
Return to privileged EXEC mode.
Verify the change.
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
Catalyst 2950 Desktop Switch Software Configuration Guide
Configuring LRE Ports
High Noise
SNR
20
26
34
20
26
34
20
26
20
20
26
20
32
32
20
20
20
10-13