JUNOS High Availability

Rapid Spanning Tree Protocol

Spanning tree protocols provide loop prevention for Layer 2 networks with multiple paths. The original Spanning Tree Protocol (STP) does this well; however, it is not up to the requirements of today’s high availability networks. Specifically, failure detection takes too long (several seconds) and reconvergence involves several stages, lasting almost a minute, during which time traffic does not flow.

Spanning Tree Fundamentals

This book assumes you have good knowledge of routing and switching protocols. Should you want or need more information on the various spanning tree protocols, you can find a wide range of material on the Internet. You can also learn more about the protocol and its implementation on JUNOS devices by attending Juniper Networks training courses.

For more information on Juniper Networks training, see http://www.juniper.net/training.

As the requirement for minimal downtime has increased, so has the need for an improved protocol. Rapid Spanning Tree Protocol (RSTP) is one of the answers to this requirement. RSTP eliminates the STP phases that require the switch to “listen and learn” after a topology change. Instead, a switch running RSTP knows its alternate path options before the failure occurs. When a failure occurs on a device, this increased “intelligence” allows the switch to provide subsecond failover—talk about a huge improvement for high availability environments!

MX Series and EX Series devices support switching along with Layer 2 ...