Dell PowerConnect B-RX Configuration Manual page 467

You can use the Fast Uplink feature on a Brocade device deployed as a wiring closet switch to
decrease the convergence time for the uplink ports to another device to just four seconds (two
seconds for listening and two seconds for learning). The wiring closet switch must be a Brocade
device but the device at the other end of the link can be a Brocade device or another vendor's
switch. Configuration of the Fast Uplink Span feature takes place entirely on the Brocade device.
To configure the Fast Uplink Span feature, specify a group of ports that have redundant uplinks on
the wiring closet switch (Brocade device) as members of a Fast Uplink Group. If the active link
becomes unavailable, the Fast Uplink Span feature transitions the forwarding to one of the other
ports in four seconds. You can configure one Fast Uplink Span group on the device. All Fast Uplink
Span ports are members of the same Fast Uplink Span group.
NOTE
To avoid the potential for temporary bridging loops, Brocade 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 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.
Fast uplink span rules for trunk groups
If you add a port to a Fast Uplink Span group that is a member of a trunk group, the following rules
apply:
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•
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Configuring a fast uplink port group
To enable Fast Uplink, use the following method.
BigIron RX Series Configuration Guide
53-1002253-01
If you add the primary port of a trunk group to the Fast Uplink Span group, all other ports in the
trunk group are automatically included in the group. Similarly, if you remove the primary port in
a trunk group from the Fast Uplink Span group, the other ports in the trunk group are
automatically removed from the Fast Uplink Span group.
You cannot add a subset of the ports in a trunk group to the Fast Uplink Span group. All ports
in a trunk group have the same Fast Uplink Span property, as they do for other port properties.
If the working trunk group is partially down but not completely down, no switch-over to the
backup occurs. This behavior is the same as in the standard STP feature.
If the working trunk group is completely down, a backup trunk group can go through an
accelerated transition only if the following are true:
•
The trunk group is included in the fast uplink group.
•
All other ports except those in this trunk group are either disabled or blocked. The
accelerated transition applies to all ports in this trunk group.
When the original working trunk group comes back (partially or fully), the transition back to the
original topology is accelerated if the conditions listed above are met.
Configuring RSTP parameters
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