Manufacture Corporation 94-1518PF, User Manual

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Chapter 8 Spanning tree
The Spanning Tree Protocol (STP) can be used to detect and disable network loops, and to
provide backup links between switches, bridges or routers. This allows the switch to interact
with other bridging devices (that is, an STP-compliant switch, bridge or router) in your
network to ensure that only one route exists between any two stations on the network, and
provide backup links which automatically take over when a primary link goes down.
STP - STP uses a distributed algorithm to select a bridging device (STP- compliant switch, bridge
or router) that serves as the root of the spanning tree network. It selects a root port on each
bridging device (except for the root device) which incurs the lowest path cost when forwarding
a packet from that device to the root device. Then it selects a designated bridging device from
each LAN which incurs the lowest path cost when forwarding a packet from that LAN to the
root device. All ports connected to designated bridging devices are assigned as designated
ports. After determining the lowest cost spanning tree, it enables all root ports and designated
ports, and disables all other ports. Network packets are therefore only forwarded between root
ports and designated ports, eliminating any possible network loops.
Figure 8: The Spanning Tree Protocol
Once a stable network topology has been established, all bridges listen for Hello BPDUs (Bridge
Protocol Data Units) transmitted from the Root Bridge. If a bridge does not get a Hello BPDU
after a predefined interval (Maximum Age), the bridge assumes that the link to the Root Bridge
is down. This bridge will then initiate negotiations with other bridges to reconfigure the network
to reestablish a valid network topology.
8-1 State
The section describes that you can select enable spanning tree protocol or not, and you can
select what protocol version you want.
Web Interface
To configure the Spanning Tree Protocol version in the web interface:
1. Click Spanning Tree and state.
2. Evoke to enable or disable the Spanning Tree Protocol.
3. Select the Spanning Tree Protocol version.
4. Click the apply to save the setting.
5. If you want to cancel the setting then you need to click the Reset button. It will revert to
previously saved values.