Product guide

Spanning-Tree Operation
The RSTP (802.1w) and STP (802.1D) Spanning Tree Options (5300xl, 3400/6400cl switches)
STP (802.1D)
STP is supported on the Series 5300xl, 3400cl and 6400cl switches.
The IEEE 802.1D version of spanning tree has been in wide use and can coexist
in a network in which RSTP (802.1w) has been introduced. If your network
currently uses 802.1D STP and you are not yet ready to implement RSTP, you
can apply STP to the switch until such time as you are ready to move ahead
with RSTP. STP on the switches covered by this guide offers the full range of
STP features found in earlier product releases, including:
■ STP Fast Mode for Overcoming Server Access Failures: If an end
node is configured to automatically access a server, the duration of the
STP startup sequence can result in a “server access failure”. On ports
where this is a problem, configuring STP Fast Mode can eliminate the
failure. For more information, see “STP Fast Mode” on page 6-29. The next
sections describe how to configure STP on the switch. For more informa-
tion on STP operation, see “How STP and RSTP Operate on the 5300xl,
3400cl and 6400cl Switches” on page 6-8.
■ Fast-Uplink STP for Improving the Recovery (Convergence) Time
in Wiring Closet Switches with Redundant Uplinks: This means that
a switch having redundant links toward the root device can decrease the
convergence time to a new uplink port to as little as ten seconds. For more
information, refer to “Fast-Uplink Spanning Tree Protocol (STP)” on
page 6-30.
How STP and RSTP Operate on the 5300xl,
3400cl and 6400cl Switches
The switch automatically senses port identity and type, and automatically
defines spanning-tree parameters for each type, as well as parameters that
apply across the switch. You can use the default values for these parameters,
or adjust them as needed.
While allowing only one active path through a network at any time, spanning
tree retains any redundant physical path to serve as a backup (blocked) path
in case the existing active path fails. Thus, if an active path fails, spanning tree
automatically activates (unblocks) an available backup to serve as the new
active path for as long as the original active path is down. For example:
6-8