Cisco WS-C2955T-12 Software Manual page 218

Configuring the LRE Ports
We recommend using one of these six private profiles (LRE-5, LRE-10, LRE-15, LRE-10-1,
•
LRE-10-3, and LRE-10-5) when the link between the LRE switch and the CPE does not need to
coexist in the same cable bundle as Asymmetric Digital Subscriber Line (ADSL) signaling.
For these profiles, the LRE downstream channel operates between 900 kHz and 3.5 MHz and
between 4 MHz and 8 MHz.
The symmetric profiles (LRE-5, LRE-10, LRE-15) provide full-duplex throughput on the link
•
between the LRE switch and CPE. Under ideal conditions, this can mean up to 30 Mbps of
bandwidth on the LRE link if you are using the LRE-15 profile.
Note
Note
• We recommend using the ANSI and ETSI asymmetric public profiles for North America and other
countries, respectively, when LRE signaling needs to coexist with ADSL signaling. We also
recommend using a public profile when the PBX is not on-site and the POTS splitter directly
connects to the PSTN. This guarantees that the LRE upstream frequency band cuts off at 5.2 MHz
allowing the LRE upstream signal to be spectrally compatible with ADSL in the same cable bundle.
Note
The LRE link must have a minimum signal-to-noise ratio (SNR) to operate. Link is not established
•
if the SNR is insufficient. Each profile requires a different minimum SNR ratio
Table 7-2
Profile
Public-ANSI
Public-ETSI
LRE-5 and LRE-5LL
LRE-10, LRE-10-1, LRE-10-3, LRE-10-5, and LRE-10LL
LRE-15 and LRE-15LL
Use the show controllers lre privileged EXEC commands to display the LRE link statistics and profile
information on the LRE ports. For information about these commands, refer to the switch command
reference.
Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
7-20
Avoid using the symmetric profiles when the LRE switch and CPE link need to coexist in the
same cable bundle with ADSL signaling. Cross talk and interference across wire pairs in cable
bundles can degrade Ethernet performance.
All POTS telephones not directly connected to the CPE require microfilters with a 300-ohm
termination. Microfilters improve voice call quality when voice and data equipment are using
the same telephone line. They also prevent nonfiltered telephone rings and nonfiltered telephone
transitions (such as on-hook to off-hook) from interrupting the LRE connection.
LRE signaling can coexist with ADSL signaling in the same cable bundle. However, LRE
signaling is not compatible with T1 signals in the same cable bundle.
Minimum SNR Ratios
Chapter 7 Configuring the Switch Ports
(Table
Minimum SNR
Local 19 db, remote 25 db
Local 19 db, remote 25 db
Local 13 db, remote 19 db
Local 19 db, remote 25 db
Local 25 db, remote 31 db
7-2).
78-6511-08