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Catalyst2950 and Catalyst2955 Switch Software Configuration Guide
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Chapter13 Configuring LRE Configuring LRE Ports
Default LRE Configuration
This is the default LRE configuration:
•On the Catalyst 2950ST-8 LRE and the Catalyst 2950ST-24 LRE switches, the profile on all LRE
ports is LRE-10.
•On the Catalyst 2950ST-24 LRE 997 switches, the profile on all LRE ports is LRE-6.
•Global profiles and global sequences are not assigned to LRE ports.
•Per-port sequences are not assigned to specific LRE ports.
•Rate selection is enabled on all interfaces, but a sequence with which to start rate selection is not
defined.
•LRE link persistence is enabled. The default is 3 seconds.
•LRE link monitoring is enabled.
•The interleave block size is 16 for non low-latency (LL) profiles and 0 for L L pr ofiles.
•For the upstream power back-off mechanism, the default noise model is the ETSI-E model (av ailable
only on the Catalyst 2950ST-24 LRE 997 switch).
•CPE toggle is enabled on a CPE Ethernet link.
•Syslog export is disabled.
Environmental Guidelines for LRE Links
The guidelines for your LRE environment are based on these factors:
•Maximum distance between the LRE switch and CPE devices—LRE runs on Category 1, 2, and 3
structured and unstructured cable. The maximum distance supported on the LRE link i s fro m 35 00
to 5000 feet (1524mete rs), depe nding on the profile. The hi gher the rate, the sho rter th e distan ce.
In buildings where LRE traffic runs over bundled telco cabling, the maximum distance is
approximately 30 percent lower.
Each terminated bridge tap in a room can further reduce LRE link dista nces by 300feet (91 meters).
The quality of the cable, the size of the cable bundles, and cross talk within the bundle also can affect
overall reach.
•Site type—If your site has either a private branch exchange (PBX) providing telephone service
throughout or has direct connections to the PSTN, you must identify the requir ements of your local
public telephone service provider.
If your site is a single building (or is a connected set of buildings), consult a qualified electrician to
ensure that the wiring conforms to the appropriate regul ati on s f or indoo r cir cuit s.
If your site has separate buildings, you must determine how the buildings are ca ble d to ea ch o th er.
Where the wiring between the LRE switch and CPE device leaves the building (or the armored
conduits certified for inside wiring standards), it must be protecte d aga inst light nin g a nd sh ort s to
high-voltage power. This protection might be provided by fuses or overvoltage protectors that
comply with local regulations for outside wiring protection. Consult an expert in local
telecommunications regulations for the details of this protection.