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12-6
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
OL-10101-02
Chapter 12 Configuring LRE
Understanding LRE Features
Beginning with the first profile in a sequence, the switch attempts to apply each profile within that
sequence to the LRE interface. The switch continues these attempts until it converges (convergence time
refers to the time required for the switch to settle on an appropriate profile for the LRE interface). The
link is DOWN until a link is established by one of the profiles in the sequence, after which, it is UP.
For additional information on rate selection, see the “Using Rate Selection to Automatically Assign
Profiles” section on page 12-14.
CPE Ethernet Links
The CPE Ethernet link settings define the connection between the CPE Ethernet port and a remote
Ethernet device, such as a PC.
Note From the CLI, you can configure and monitor the Ethernet link on a Cisco 575 LRE CPE and the
Cisco
585 LRE CPE. You can configure and monitor the Ethernet link on a Cisco 576 LRE 997 CPE only
from the CLI. For information about the switch LEDs, see the Catalyst 2950 Desktop Switch Hardware
Installation Guide.
Keep these considerations in mind when you have CPE devices connected to the LRE ports:
• Use the shutdown interface configuration command to disable the LRE interface transmitter on any
LRE ports. This prevents access to the LRE port and prevents the power emitted from the port from
affecting other ports.
• You cannot configure the flow-control setting on the LRE ports. The flow-control setting on the CPE
Ethernet port is automatically disabled in half-duplex mode and is automatically enabled in
full-duplex mode.
• Certain CPEs do not work with certain switches. For details, see the LRE switch and CPE
compatibility matrix (see
Table 1-2 on page 1-2). You can connect Cisco 575 LRE CPEs and
Cisco 585 LRE CPEs to the Catalyst 2950ST-8 LRE or 2950ST-24 LRE switch. You can connect a
Cisco 576 LRE 997 CPE only to a Catalyst 2950ST-24 LRE 997 switch.
• You can hot-swap the CPE devices without powering down the switch or disrupting the other switch
ports.
• The CPE toggle feature automatically changes a CPE Ethernet link from down to up if the LRE link
comes up in less than 30 seconds. This feature is enabled by default.
LRE-9-6 LRE-9-6 LRE-6-3 LRE-6 LRE-9-4
LRE-9-4 LRE-9-4 LRE-4-3 LRE-9-4 LRE-9-3
LRE-6 LRE-9-3 LRE-6-4
LRE-6-4 LRE-6 LRE-4
LRE-9-3 LRE-6-4 LRE-12-3
LRE-4 LRE-6-3 LRE-9-3
LRE-6-3 LRE-4 LRE-6-3
LRE-4-3 LRE-4-3 LRE-4-3
Table 12-4 LRE Rate Selection Sequences for the Catalyst 2950ST-24 LRE 997 Switches (continued)
LRE-SEQ-
COMPLETE-REACH
LRE-SEQ-
DOWNSTREAM LRE-SEQ-SYM
LRE-SEQ-SYM-
LONGREACH
LRE-SEQ-
UPSTREAM
LRE-SEQ-
VIDEO-TRANSMIT1