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Cisco Systems IntelligentGigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
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Chapter24 Configuring EtherChann els and Layer 2 Trunk Failover
Understanding EtherChannels
Figure24-2 Relationship of Physical Ports, Logical Port Channels, and Channel Groups
When a port joins an EtherChannel, the physical interface for that port is shut down. When the port
leaves the port-channel, its physical interface is brought up, and it has the same configuration as it had
before joining the EtherChannel.
Note Configuration changes made to the logical interface of an EtherChann el might not propagate to all the
member ports of the channel.
Understanding the Port Aggregation Protocol and Link Aggregation ProtocolThe Port Aggregation Protocol (PAgP) and Link Aggregation Control Protocol (LACP) facilitate the
automatic creation of EtherChannels by exchanging packets b etween Ethernet interfaces. PAgP is a
Cisco-proprietary protocol that can be run only on Cisco switc hes and on those switches licensed by
licensed vendors to support PAgP. LACP is defined in IEEE 802.3ad and allows Cisco switches to
manage Ethernet channels between switches that conform to the I EEE 802.3ad protocol.
By using one of these protocols, a switch learns the identi ty of partners capable of supporting either
PAgP or LACP and learns the capabilities of each interface. It then dynamically groups similarly
configured interfaces into a single logical link (channel or aggregate port). These interfaces are grouped
based on hardware, administrative, and port parameter constraints. For example, PAgP groups the
interfaces with the same speed, duplex mode, native VLAN, VLAN range, and trunking status and type.
After grouping the links into an EtherChannel, PAgP adds the group to the span ning tree as a single
switch port.
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Channel-group
binding
Physical ports
Logical
port-channel