Lacp Interaction With Other Features - Cisco Catalyst 2960 series Configuration Manual

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.
Caution You should use care when using the on mode. This is a manual configuration, and ports on both ends of
the EtherChannel must have the same configuration. If the group is misconfigured, packet loss or
spanning-tree loops can occur.
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. You
can specify one of several different load-balancing modes, including load distribution based on MAC addresses,
IP addresses, source addresses, 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.
Related Topics
Configuring EtherChannel Load-Balancing
EtherChannel Configuration Guidelines, on page 338
Layer 2 EtherChannel Configuration Guidelines, on page 340
Default EtherChannel Configuration, on page 337
MAC Address Forwarding
With source-MAC address forwarding, when packets are forwarded to an EtherChannel, they are distributed
across the ports in the channel based on the source-MAC address of the incoming packet. Therefore, to provide
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
Information About EtherChannels
333