Understanding The Lacp; Lacp Modes - Cisco WS-C2950SX-48-SI Configuration Manual

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
----- ---------- --------- ----------- ------------------------- ----------
2/1
2/2
----- ---------- --------- ----------- ------------------------- ----------
Switch_A> (enable)
Switch_B> (enable) show port channel
Port
----- ---------- --------- ----------- ------------------------- ----------
3/1
3/2
----- ---------- --------- ----------- ------------------------- ----------
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

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
Table 6-2
Mode
on
off
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
6-16
Status Channel Channel
mode status
connected on channel
connected on channel
Status Channel Channel
mode status
connected on channel
connected on channel
"Understanding the PAgP" section on page
describes the EtherChannel modes that use LACP.
EtherChannel Modes That Use LACP
Description
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.
Mode that prevents the port from channeling.
Chapter 6 Configuring Fast EtherChannel and Gigabit EtherChannel
Neighbor
device
WS-C4003 JAB023806LN(
WS-C4003 JAB023806LN(
Neighbor
device
WS-C4003 JAB023806JR(
WS-C4003 JAB023806JR(
6-5.
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Release 8.1
Neighbor
port
3/1
3/2
Neighbor
port
2/1
2/2
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