Lantech LGS-2816C-RPS, Руководство пользователя

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C
ONFIGURING
S
PANNING
T
REE
P
ROTOCOL
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.
This switch supports Rapid Spanning Tree Protocol (RSTP), but is
backward compatible with Spanning Tree Protocol (STP).
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.
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.
RSTP - RSTP is designed as a general replacement for the slower,
legacy STP. RSTP is also incorporated into MSTP (Multiple Spanning
Tree Protocol). RSTP achieves must faster reconfiguration (i.e., around
1 to 3 seconds, compared to 30 seconds or more for STP) by reducing
the number of state changes before active ports start learning,
predefining an alternate route that can be used when a node or port
fails, and retaining the forwarding database for ports insensitive to
changes in the tree structure when reconfiguration occurs.