Aggregating for Link Redundancy
Virtual Link Aggregation
514
G8264CS Application Guide for ENOS 8.4
Multiple switch ports can be combined together to form robust, high‐bandwidth
LAGs to other devices. Since LAGs are comprised of multiple physical links, the
LAG is inherently fault tolerant. As long as one connection between the switches is
available, the LAG remains active.
In Figure
57, four ports are aggregated together between the switch and the
enterprise routing device. Connectivity is maintained as long as one of the links
remain active. The links to the server are also aggregated, allowing the secondary
NIC to take over in the event that the primary NIC link fails.
Figure 57. Aggregating Ports for Link Redundancy
For more information on aggregation, see Chapter 9, "Ports and Link
Aggregation."
Using the VLAG feature, switches can be paired as VLAG peers. The peer switches
appear to the connecting device as a single virtual entity for the purpose of
establishing a multi‐port LAG. The VLAG‐capable switches synchronize their
logical view of the access layer port structure and internally prevent implicit loops.
The VLAG topology also responds more quickly to link failure and does not result
in unnecessary MAC flooding.
VLAGs are useful in multi‐layer environments for both uplink and downlink
redundancy to any regular LAG‐capable device. They can also be used in for
active‐active VRRP connections.
For more information on VLAGs, see Chapter 11, "Virtual Link Aggregation
Groups."