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10-2
Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter10 Configuring LRE
LRE Links and LRE Profiles
LRE Links and LRE Profiles
The LRE link settings define the connection between the switch LRE port and the CPE RJ-11 wall port.
The LRE link provides symmetric and asymmetric bandwidth for data, voice, and video traffic.
Symmetric transmission is when the downstream and upstream bandwidths are the same. Asymmetric
transmission is when the downstream and the upstream bandwidths differ. Downstream transmission
refers to the traffic going from the LRE switch to the CPE device. Upstream transmission refers to the
traffic going from the CPE device to the LRE switch.
The switch controls upstream and downstream rates on the LRE link by using configurations called
profiles. Depending on the profile, the upstream and downstream bands on an LRE link can range from
approximately 1 Megabit per second (Mbps) to 18.750 Mbps.
This section discusses these topics:
• LRE Profiles, page 10-2
• LRE Sequences, page 10-4
• CPE Ethernet Links, page 10-5
LRE Profiles
You can assign profiles on a per-port or switch-wide basis. When the LRE switch establishes a link with
the CPE device, the switch downloads its profile settings to the CPE device so that the switch and CPE
device operate with the same configuration.
The LRE switches are shipped with system-defined profiles. You can configure a profile on either a
global or per-port basis. By default, all LRE ports on the switch are enabled with the LRE-10 profile.
This default profile allows the upstream and downstream transmission rate on the LRE link to be
12.5 Mbps.
Table 10-1 contains the full list of LRE profiles, as well as their downstream and upstream rates (in Mbps
and their theoretical upstream and downstream signal-to-noise (SNR) rates (in decibels).
Note Consult the regulations for connecting to the PSTN in your area.
Note Use the rates and distances in Table 10-1 as guidelines only. Factors such as the type of cable that you
use, how it is bundled, and the interference and noise on the LRE link can affect the actual LRE link
performance. Contact Cisco Systems for information about limitations and optimization of LRE link
performance. The downstream and upstream rates in the table are slightly less than the gross data rates
displayed by the show controllers lre profile names privileged EXEC command.