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Configuring Ethernet link aggregation
Ethernet link aggregation bundles multiple physical Ethernet links into one logical link, called an
aggregate link. Link aggregation has the following benefits:
•
Increased bandwidth beyond the limits of any single link. In an aggregate link, traffic is distributed
across the member ports.
•
Improved link reliability. The member ports dynamically back up one another. When a member
port fails, its traffic is automatically switched to other member ports.
As shown in
, Device A and Device B are connected by three physical Ethernet links. These
physical Ethernet links are combined into an aggregate link called link aggregation 1. The bandwidth of
this aggregate link can reach up to the total bandwidth of the three physical Ethernet links. At the same
time, the three Ethernet links back up one another. When a physical Ethernet link fails, the traffic
previously carried on the failed link is switched to the other two links.
Figure 8
Ethernet link aggregation diagram
Basic concepts
Aggregation group, member port, and aggregate interface
Link bundling is implemented through interface bundling. An aggregation group is a group of Ethernet
interfaces bundled together, which are called member ports of the aggregation group. For each
aggregation group, a logical interface (called an aggregate interface), is created. For an upper layer
entity that uses the link aggregation service, the following rules apply:
•
An aggregate link appears the same as a single logical link.
•
An aggregate interface transmits data traffic.
When you create an aggregate interface, the device automatically creates an aggregation group of the
same type and number as the aggregate interface. For example, when you create aggregate interface
1, aggregation group 1 is created.
Aggregate interfaces include Layer 2 aggregate interfaces and Layer 3 aggregate interfaces.
You can assign Layer 2 Ethernet interfaces only to a Layer 2 aggregation group, and Layer 3 Ethernet
interfaces only to a Layer 3 aggregation group.
On a Layer 3 aggregate interface, you can create subinterfaces.
NOTE:
You can use the
port link-mode
command to configure an Ethernet port as a Layer 2 or Layer 3 interface
Configuring Ethernet interfaces
