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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 10 Configuring LRE Configuring LRE Ports
The margin ra nge for link qu alificatio n is from 1 to 10 dB. The re comme nded value in a low-noise
en vironment is 2 dB. The recommended value for medium noise environment is 4 dB. The recommended
value in a high no ise environmen t is 6 dB.
If a p rofile ha s a th eo retic al minim um of 25 d B and yo u c on figure a ma rgin of 3 dB, w hen th e l ink 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
sequenc e i s a ttem pted . If you c on figure a ma rgin of 0 (t he de fau lt value) , IO S d oes n ot c heck f or the
SNR value when the link is established.
Beginning i n privileged E X EC mo de , follow these s teps to a ssign a m argin t o a spe cific LRE po rt:
Table 10-4 SNR Requirements for Upstream Rates
Profile Gross Data
Rate QAM Theo retica l
Minimum SNR Low No is e SNR Medium No ise
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 globa l configurati on mode.
Step 2 interface LRE-interface Enter interface configuration mode, an d enter the number of the
LRE po rt to b e co nfigured .
Step 3 margin [downstre am value | upstream value] Enter the downstre am or upstre am margin value (in dB)
Step 4 end Return to privileged EXEC mode.
Step 5 show controllers lre profile details Verify the change.