Stp/Rstp - Tripp Lite NGI-S04C2 Owner's Manual

4.3.2.

STP/RSTP

Introduction
(R)STP detects and breaks network loops and provides backup links between switches,
bridges or routers. It allows a Switch to interact with other (R)STP compliant switches in
your network to ensure that only one path exists between any two stations on the
network.
The Switch supports Spanning Tree Protocol (STP) and Rapid Spanning Tree Protocol
(RSTP) as defined in the following standards.
IEEE 802.1D Spanning Tree Protocol

IEEE 802.1w Rapid Spanning Tree Protocol

The Switch uses IEEE 802.1w RSTP (Rapid Spanning Tree Protocol) that allows faster
convergence of the spanning tree than STP (while also being backwards compatible with
STP-only aware bridges). In RSTP, topology change information is directly propagated
throughout the network from the device that generates the topology change. In STP, a
longer delay is required as the device that causes a topology change first notifies the root
bridge and then the root bridge notifies the network. Both RSTP and STP flush unwanted
learned addresses from the filtering database.
In STP, the port states are Blocking, Listening, Learning, Forwarding.
In RSTP, the port states are Discarding, Learning, and Forwarding.
Note: In this document, "STP" refers to both STP and RSTP.
STP Terminology
The root bridge is the base of the spanning tree.

Path cost is the cost of transmitting a frame onto a LAN through that port. The

recommended cost is assigned according to the speed of the link to which a port
is attached. The slower the media, the higher the cost.
On each bridge, the bridge communicates with the root through the root port.

The root port is the port on this Switch with the lowest path cost to the root (the
root path cost). If there is no root port, then this Switch has been accepted as
the root bridge of the spanning tree network.
For each LAN segment, a designated bridge is selected. This bridge has the

lowest cost to the root among the bridges connected to the LAN.
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