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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
OL-9639-07
Chapter 34 Configuring EtherChannels and Link-State Tracking
Understanding EtherChannels
You can configure an EtherChannel in one of these modes: Port Aggregation Protocol (PAgP), Link
Aggregation Control Protocol (LACP), or On mode. PAgP and LACP are available only on NNIs and
ENIs. 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 suspended.
•
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.
The local port is put into an independent state and continues 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.
If a link within an EtherChannel fails, traffic previously carried over that failed link changes to the
remaining links within the EtherChannel. A trap is sent for a failure, identifying 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.
Port-Channel Interfaces
When you create an EtherChannel, a port-channel logical interface is involved:
•
With Layer 2 ports, use the
channel-group
interface configuration command to dynamically create
the port-channel logical interface.
You also can use the
interface port-channel
port-channel-number
global configuration command
to manually create the port-channel logical interface, but then you must use the
channel-group
channel-group-number
command to bind the logical interface to a physical port. The
channel-group-number
can be the same as the
port
-
channel-number,
or you can use a new number.
If you use a new number, the
channel-group
command dynamically creates a new port channel.
•
With Layer 3 ports, you should manually create the logical interface by using the
interface
port-channel
global configuration command followed by the
no switchport
interface configuration
command. Then you manually assign an interface to the EtherChannel by using the
channel-group
interface configuration command.
For both Layer 2 and Layer 3 ports, the
channel-group
command binds the physical port and the logical
interface together as shown in
Figure 34-2
.
Note
The switch must be running the metro IP access image to support Layer 3 ports.
Each EtherChannel has a port-channel logical interface numbered from 1 to 48. This port-channel
interface number corresponds to the one specified with the
channel-group
interface configuration
command.
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