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LACP automatically configures an administrative key value equal to the channel
group identification number on each port configured to use LACP. The adminis-
trative key defines the capability of a port to aggregate with other ports, which
is determined by the following configuration restrictions that you establish:
■
Port physical characteristics such as data rate
■
Duplex capability
■
Point-to-point or shared medium
d. Set the EtherChannel mode:
interface [mod[/port]]
channel-group number mode {active | on | {auto [non-silent]} | {desirable
[non-silent]} | passive}
LACP can be configured in one of these modes: on (EtherChannel is used, but
no LACP packets are sent), off (EtherChannel is disabled), active (switch is
actively willing to form an EtherChannel; LACP packets are sent), or passive
(switch is passively willing to form an EtherChannel; no LACP packets are sent;
the default).
Tip Although PAgP and LACP are not compatible or interoperable, you can
form an EtherChannel between one switch that uses PAgP on a module and
another switch that uses LACP on its module. In this case, set the PAgP switch
to the on mode and the LACP switch to the on mode. Neither protocol will be
used to negotiate an EtherChannel, but the EtherChannel will be formed.
EtherChannel Example
Figure 4-1 shows a network diagram for this example. A switch has three line cards with
Ethernet ports. Modules 4 and 5 use PAgP to aggregate ports, whereas module 6 uses
LACP. One EtherChannel is made up of ports 4/1, 4/2, 5/1, and 5/2, demonstrating that
an EtherChannel can be split across multiple line cards. This EtherChannel uses PAgP in
the desirable mode to dynamically bundle the ports together. The nonsilent mode
requires a PAgP speaker on the far end before the EtherChannel will be built. Both source
and destination IP addresses distribute traffic across the bundled ports.
Figure 4-1 Network Diagram for the EtherChannel
Example
PAgP
EtherChannel
Catalyst
4/1
6/1
4/2
6/2
6/7
5/1
5/2
6/8
Chapter 4: Layer 2 Interface Configuration 67
LACP
EtherChannel
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