Link Aggregation Control Protocol - Cisco Catalyst 2960 series Configuration Manual

Information About EtherChannels
PAgP sends and receives PAgP PDUs only from ports that are up and have PAgP enabled for the auto or
desirable mode.

Link Aggregation Control Protocol

The LACP is defined in IEEE 802.3ad and enables Cisco switches to manage Ethernet channels between
switches that conform to the IEEE 802.3ad protocol. LACP facilitates the automatic creation of EtherChannels
by exchanging LACP packets between Ethernet ports.
By using LACP, the switch or switch stack learns the identity of partners capable of supporting LACP and
the capabilities of each port. It then dynamically groups similarly configured ports into a single logical link
(channel or aggregate port). Similarly configured ports are grouped based on hardware, administrative, and
port parameter constraints. For example, LACP groups the ports with the same speed, duplex mode, native
VLAN, VLAN range, and trunking status and type. After grouping the links into an EtherChannel, LACP
adds the group to the spanning tree as a single switch port.
LACP Modes
LACP modes specify whether a port can send LACP packets or only receive LACP packets.
Table 37: EtherChannel LACP Modes
Mode
active
passive
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, based on trunk 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:
• 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.
Related Topics
Configuring Layer 2 EtherChannels , on page 342
EtherChannel Configuration Guidelines, on page 338
Default EtherChannel Configuration, on page 337
Layer 2 EtherChannel Configuration Guidelines, on page 340
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
332
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.