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6-16
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
—
Release 8.1
78-15486-01
Chapter 6 Configuring Fast EtherChannel and Gigabit EtherChannel
Understanding the LACP
Step 4
After the EtherChannel bundle is negotiated, enter the show port channel command to verify the
configuration. If you configure only the ports on one side of the link on, the show port channel
command will show that the ports are channeling, but no traffic will pass over the EtherChannel.
Spanning tree loops can occur, and eventually the switch will disable the incorrectly configured
EtherChannel.
Switch_A> (enable) show port channel
Port Status Channel Channel Neighbor Neighbor
mode status device port
----- ---------- --------- ----------- ------------------------- ----------
2/1 connected on channel WS-C4003 JAB023806LN( 3/1
2/2 connected on channel WS-C4003 JAB023806LN( 3/2
----- ---------- --------- ----------- ------------------------- ----------
Switch_A> (enable)
Switch_B> (enable) show port channel
Port Status Channel Channel Neighbor Neighbor
mode status device port
----- ---------- --------- ----------- ------------------------- ----------
3/1 connected on channel WS-C4003 JAB023806JR( 2/1
3/2 connected on channel WS-C4003 JAB023806JR( 2/2
----- ---------- --------- ----------- ------------------------- ----------
Switch_B> (enable)
Understanding the LACP
Use the information in these sections if you are configuring EtherChannel using LACP. If you are using
PAgP, see the
“Understanding the PAgP” section on page 6-5
.
LACP Modes
You may manually turn on channeling by setting the port channel mode to on, and you may turn
channeling off by setting the port channel mode to off.
If you want LACP to handle channeling, use the active and passive channel modes. To start automatic
EtherChannel configuration with LACP, you need to configure at least one end of the link to active mode
to initiate channeling, because ports in passive mode passively respond to initiation and never initiate
the sending of LACP packets.
Table 6-2
describes the EtherChannel modes that use LACP.
Table 6-2
EtherChannel Modes That Use LACP
Mode
Description
on
Mode that forces the port to channel without LACP. With the on mode, a usable
EtherChannel exists only when a port group in on mode is connected to another port group
in on mode.
off
Mode that prevents the port from channeling.