Multilayer switches combine the benefits of switching and routing on a
single hardware platform and can enhance overall network performance when
deployed properly. Multilayer switches provide very high speed Layer 2 and
Layer 3 functionality by "caching" much of the forwarding information
between sources and destinations.
Here are issues that exist when a
multilayer switch is deployed in an improperly designed network.
- Multilayer switches, by condensing the functions of switching and routing
into a single chassis, can create single points of failure if redundancy for
these devices is not carefully planned and implemented.
- Switches in a flat network are interconnected creating many paths between
destinations. If active, these potential redundant paths will create bridging
loops. To control this, the network must run a Spanning Tree Protocol (STP).
Networks that use the IEEE 802.1d protocol may experience periods of
disconnection and frame flooding during topology change.
- Multilayer switch functionality may be underutilized if a multilayer switch
is simply a replacement to the traditional role of a router in a
non-hierarchical network.