VSX in the core layer

VSX LAG in the core (recommended)

When mobility controllers are attached to the core layer, a VSX LAG must be in the core level. Layer 2 is only at the distribution layer with the core layer being layer 2 and layer 3. This configuration is for IPv6, and the configuration reduces the number of transit VLANs and the associated SVIs for many VRFs. It also minimizes the Sender Policy Framework (SPF) calculation. The number of fibers is reduced and there is fast failover because of the simplified topology (no square-routing).

A VSX LAG is shown in the core.

The following image shows an example that SPF is slower when VSX is not in the core because of routing convergence.

VSX LAG not in the core

A VSX LAG is not in the core