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CHAPTER 6: 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 that
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) that 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
that 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.
Designated root
Designated bridge
Designated port
Root port
FIGURE 6-1. 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.
6.1 STP CONFIGURATION
The section describes how to enable or disable spanning tree protocol. You can select the protocol version you need.
WEB INTERFACE
To configure the Spanning Tree Protocol version in the web interface:
1. Click Spanning Tree and STP Configuration.
2. Scroll to select the parameters and enter the available value of parameters in the blank field in Basic Settings.
3. Enable or disable the parameters and enter the available value of parameters in the blank field in Advanced settings.
4. Click apply to save the setting.
5. To cancel the setting, click the Reset button. It will revert to previously saved values
