37-7
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
OL-12247-04
Chapter 37 Configuring EtherChannels and Link-State Tracking
Understanding EtherChannels
LACP Modes
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. For Layer 3 EtherChannels, the MAC address is allocated by the
stack master as soon as the interface is created through the
interface port-channel
global configuration
command.
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.
Table 37-2
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.