Describing the Campus Infrastructure Module
Issues with multilayer switches in a nonhierarchical network

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.