S Panning T Ree - Black Box LPB2910A User Manual

2-­‐8 S panning T ree
Spanning T ree P rotocol ( STP) c an b e u sed t o d etect a nd d isable n etwork l oops, a nd t o p rovide b ackup
links b etween s witches, b ridges, o r r outers. T his a llows t he s witch t o i nteract w ith o ther b ridging
devices ( that i s, a n S TP-­‐compliant s witch, b ridge, o r r outer) i n y our n etwork t o e nsure t hat o nly o ne
route e xists b etween a ny t wo s tations o n t he n etwork, a nd p rovide b ackup l inks t hat a utomatically
take o ver w hen a p rimary l ink g oes d own.
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 d evice t o t he r oot d evice. T hen i t s elects a d esignated b ridging d evice f rom e ach L AN that i ncurs
the l owest p ath c ost w hen f orwarding a p acket f rom t hat L AN t o t he r oot d evice. A ll p orts c onnected
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 n etwork l oops.
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 i nterval ( Maximum A ge), t he b ridge a ssumes t hat t he l ink t o t he R oot B ridge i s d own. T his
bridge will then initiate negotiations with other bridges to reconfigure the network to reestablish a
valid n etwork t opology.
2-­‐8.1 B ridge S etting
The section describes how to configure the Spanning Tree Bridge and STP System settings. It allows
you t o c onfigure S TP S ystem s ettings a re u sed b y a ll S TP B ridges i n t he s witch.
Web I nterface
To c onfigure t he S panning T ree B ridge S ettings p arameters i n t he w eb i nterface:
1. Click C onfiguration, S panning T ree, B ridge S ettings.
2. Scroll t o s elect t he p arameters a nd w rite d own a vailable v alue o f p arameters i n b lank f ield i n B asic
Settings.
3. Enable o r d isable t he p arameters a nd w rite d own t he a vailable v alue o f p arameters i n b lank f ield i n
Advanced s ettings.
4. Click A pply t o s ave t he s etting.
5. If y ou w ant t o c ancel t he s etting, c lick t he R eset b utton. I t w ill r evert t o p reviously s aved v alues.
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Publication date: Sept, 2015
Revision A1