Evidence Cross-8/HPoE-10G, User Manual

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Chapter 7 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 7: 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.
7-1 STP Configuration
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 STP Configuration.
2. Scroll to select the parameters and write down available value of parameters in blank field
in Basic Settings.
3. Evoke to enable or disable the parameters and write down available value of parameters
in blank field in Advanced settings.
4. Click the apply to save the setting.