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Senior Editor

Bolstering VLANs

Aug 06, 20032 mins

* 802.1s Multiple Spanning Tree Protocol

The concept of virtual LANs was introduced about eight years ago.  At the time VLANs were touted as a way to simplify address management by letting customers deploy servers and PCs anywhere across the network and tie the machines into groups virtually.

Over time VLANs are deployed in corporate networks in a variety of ways, including network security authentication, a way to let wireless clients roam among 802.11b access points, a method of segregating IP voice traffic and a way to contain legacy traffic on networks with heterogeneous protocols.

And the technology has evolved to help keep VLANs a viable option for users with lots dispersed users.  Our Technology Update author ( this week takes a look at one of the technologies that has emerged to help VLANs become more useful and stable: 802.1s Multiple Spanning Tree Protocol.

The 802.1s standard lets administrators assign VLAN traffic to different unique paths. The idea is that users can group VLANs to spanning tree networks. Each network or instance can have a topology independent of other spanning tree instances. This technology defines multiple forwarding paths for data traffic and enables load balancing amongst multiple servers or devices across VLANs. Network fault tolerance is improved because a failure in one forwarding path does not affect other instances.  In the past the loss of one VLAN path could bring down the entire environment.