Default Lre Configuration; Environmental Guidelines For Lre Links - Cisco Catalyst 2950 Software Configuration Manual

Chapter 12 Configuring LRE

Default LRE Configuration

This is the default LRE configuration:
•
•
•
•
•
•
•
•
•
•
•

Environmental Guidelines for LRE Links

The guidelines for your LRE environment are based on these factors:
•
•
78-11380-12
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 LL profiles.
For the upstream power back-off mechanism, the default noise model is the ETSI-E model (available
only on the Catalyst 2950ST-24 LRE 997 switch).
CPE toggle is enabled on a CPE Ethernet link.
Syslog export is disabled.
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 is from 3500
to 5000 feet (1524 meters), depending on the profile. The higher the rate, the shorter the distance.
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 distances by 300 feet (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 requirements 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 regulations for indoor circuits.
If your site has separate buildings, you must determine how the buildings are cabled to each other.
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 protected against lightning and shorts 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.
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
Configuring LRE Ports
12-9