Lacp Modes; Lacp Interaction With Other Features; Load Balancing And Forwarding Methods - Cisco WS-C3560-48PS-S Software Configuration Manual

Understanding EtherChannels

LACP Modes

Table 29-2
configuration command.
Table 29-2 EtherChannel LACP Modes
Mode
active
passive
on
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:
•
•

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.

Load Balancing and Forwarding Methods

EtherChannel balances the traffic load across the links in a channel by reducing part of the binary pattern
formed from the addresses in the frame to a numerical value that selects one of the links in the channel.
EtherChannel load balancing can use MAC addresses or IP addresses, source or destination addresses,
or both source and destination addresses. The selected mode applies to all EtherChannels configured on
the switch. You configure the load balancing and forwarding method by using the port-channel
load-balance global configuration command.
Catalyst 3560 Switch Software Configuration Guide
29-6
shows the user-configurable EtherChannel LACP modes for the channel-group interface
Description
Places a port into an active negotiating state in which the port starts negotiations with other
ports by sending LACP packets.
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.
Forces a port to channel without PAgP or LACP. With the on mode, a usable EtherChannel
exists only when a port group in the on mode is connected to another port group in the on
mode.
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.
Chapter 29 Configuring EtherChannels
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