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35-6
Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 35 Configuring EtherChannels and Link-State Tracking
Understanding EtherChannels
LACP Modes
Table 35-2 shows the user-configurable EtherChannel LACP modes for the channel-group interface
configuration command.
Both the active and passive LACP modes enable ports to negotiate with partner ports to an
EtherChannel based on criteria such as port speed and, for Layer
2 EtherChannels, trunking state and
VLAN numbers.
Ports can form an EtherChannel when they are in different LACP modes as long as the modes are
compatible. For example:
• A port in the active mode can form an EtherChannel with another port that is in the active or passive
mode.
• A port in the passive mode cannot form an EtherChannel with another port that is also in the passive
mode because neither port starts LACP negotiation.
LACP Interaction with Other Features
The DTP and the CDP send and receive packets over the physical ports in the EtherChannel. Trunk ports
send and receive LACP PDUs on the lowest numbered VLAN.
In Layer 2 EtherChannels, the first port in the channel that comes up provides its MAC address to the
EtherChannel. If this port is removed from the bundle, one of the remaining ports in the bundle provides
its MAC address to the EtherChannel.
LACP sends and receives LACP PDUs only from ports that are up and have LACP enabled for the active
or passive mode.
EtherChannel On Mode
EtherChannel on mode can be used to manually configure an EtherChannel. The on mode forces a port
to join an EtherChannel without negotiations. The on mode can be useful if the remote device does not
support PAgP or LACP. In the on mode, a usable EtherChannel exists only when the switches at both
ends of the link are configured in the on mode.
Ports that are configured in the on mode in the same channel group must have compatible port
characteristics, such as speed and duplex. Ports that are not compatible are suspended, even though they
are configured in the on mode.
Ta ble 35-2 EtherChannel LACP Modes
Mode Description
active Places a port into an active negotiating state in which the port starts negotiations with other
ports by sending LACP packets.
passive Places a port into a passive negotiating state in which the port responds to LACP packets
that it receives, but does not start LACP packet negotiation. This setting minimizes the
transmission of LACP packets.