Cisco Catalyst 2960 Software Configuration Manual page 865

Chapter 38 Configuring EtherChannels and Link-State Tracking
You can configure an EtherChannel in one of these modes: Port Aggregation Protocol (PAgP), Link
Aggregation Control Protocol (LACP), or On. Configure both ends of the EtherChannel in the same
mode:
When you configure one end of an EtherChannel in either PAgP or LACP mode, the system
•
negotiates with the other end of the channel to determine which ports should become active.
Incompatible ports are put into an independent state and continue to carry data traffic as would any
other single link. The port configuration does not change, but the port does not participate in the
EtherChannel.
When you configure an EtherChannel in the on mode, no negotiations take place. The switch forces
•
all compatible ports to become active in the EtherChannel. The other end of the channel (on the other
switch) must also be configured in the on mode; otherwise, packet loss can occur.
You can create an EtherChannel on a standalone switch, on a single switch in the stack, or on multiple
switches in the stack (known as cross-stack EtherChannel). See
If a link within an EtherChannel fails, traffic previously carried over that failed link moves to the
remaining links within the EtherChannel. If traps are enabled on the switch, a trap is sent for a failure
that identifies the switch, the EtherChannel, and the failed link. Inbound broadcast and multicast packets
on one link in an EtherChannel are blocked from returning on any other link of the EtherChannel.
Figure 38-2
Stack port
connections
OL-26520-01
Single-Switch EtherChannel
Catalyst 2960-S switch stack
Switch 1
Channel
group 1
Switch 2
Switch 3
Catalyst 2960 and 2960-S Switches Software Configuration Guide, Release 15.0(1)SE
Figure 38-2
Channel
group 2
Understanding EtherChannels
and Figure 38-3.
Switch A
38-3