Fast Uplink Span

The Fast Port Span feature described in the previous section enhances STP performance for end stations. The Fast Uplink Span feature enhances STP performance for wiring closet switches with redundant uplinks. Using the default value for the standard STP forward delay, convergence following a transition from an active link to a redundant link can take 30 seconds (15 seconds for listening and an additional 15 seconds for learning).

You can use the Fast Uplink Span feature on a device deployed as a wiring closet switch to decrease the convergence time for the uplink ports to another device to just one second. The new Uplink port directly goes to forward mode (bypassing listening and learning modes). The wiring closet switch must be a RUCKUS ICX device but the device at the other end of the link can be a RUCKUS ICX device or another vendor’s switch.

Configuration of the Fast Uplink Span feature takes place entirely on the RUCKUS ICX device. To configure the Fast Uplink Span feature, specify a group of ports that have redundant uplinks on the wiring closet switch (RUCKUS ICX device). If the active link becomes unavailable, the Fast Uplink Span feature transitions the forwarding to one of the other redundant uplink ports in just one second. All Fast Uplink Span-enabled ports are members of a single Fast Uplink Span group.

Note: To avoid the potential for temporary bridging loops, RUCKUS recommends that you use the Fast Uplink feature only for wiring closet switches (switches at the edge of the network cloud). In addition, enable the feature only on a group of ports intended for redundancy, so that at any given time only one of the ports is expected to be in the forwarding state.
Note: When the wiring closet switch (RUCKUS ICX device) first comes up or when STP is first enabled, the uplink ports still must go through the standard STP state transition without any acceleration. This behavior guards against temporary routing loops as the switch tries to determine the states for all the ports. Fast Uplink Span acceleration applies only when a working uplink becomes unavailable.