Spanning-Tree Operation
The RSTP (802.1w) and STP (802.1D) Spanning Tree Options
RSTP (802.1w)
The IEEE 802.1D version of spanning tree (STP) can take a fairly long time to
resolve all the possible paths and to select the most efficient path through the
network. The IEEE 802.1w Rapid Reconfiguration Spanning Tree (RSTP)
significantly reduces the amount of time it takes to establish the network path.
The result is reduced network downtime and improved network robustness.
In addition to faster network reconfiguration, RSTP also implements greater
ranges for port path costs to accommodate the higher and higher connection
speeds that are being implemented.
RSTP is designed to be compatible with IEEE 802.1D STP, and HP recom-
mends that you employ it in your network. For more information, refer to
“Transitioning from STP to RSTP” on page 6-10.
STP (802.1D)
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
6-28. 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 page 6-7.
■ 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 6-29.
6-6
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