LevelOne GSW-4876 - Manual (Page 137)

C HAPTER 4 | Configuring the Switch
Configuring the Spanning Tree Algorithm
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tree priority. Such a port will be selected as an Alternate Port after the
Root Port has been selected. If set, this can cause a lack of spanning
tree connectivity. It can be set by a network administrator to prevent
bridges external to a core region of the network influencing the
spanning tree active topology, possibly because those bridges are not
under the full control of the administrator. This feature is also know as
Root Guard.
◆ Restricted TCN – If enabled, this causes the port not to propagate
received topology change notifications and topology changes to other
ports. TCN messages can cause temporary loss of connectivity after
changes in a spanning tree’s active topology as a result of persistent
incorrectly learned station location information. TCN messages can be
restricted by a network administrator to prevent bridges external to a
core region of the network from causing address flushing in that region,
possibly because those bridges are not under the full control of the
administrator or the physical link state for the attached LANs transitions
frequently.
◆ BPDU Guard – This feature protects ports from receiving BPDUs. It
can prevent loops by shutting down an port when a BPDU is received
instead of putting it into the spanning tree discarding state. The BPDU
guard feature provides a secure response to invalid configurations
because an administrator must manually enable the port.
(Default: Disabled)
If enabled, the port will disable itself upon receiving valid BPDU's.
Contrary to the similar bridge setting, the port Edge status does not
affect this setting. A port entering error-disabled state due to this
setting is subject to the bridge Port Error Recovery setting as well (see
"Configuring Global Settings for STA" on page 128 ).
◆ Point-to-Point – The link type attached to an interface can be set to
automatically detect the link type, or manually configured as point-to-
point or shared medium. Transition to the forwarding state is faster for
point-to-point links than for shared media. These options are described
below:
■
Auto – The switch automatically determines if the interface is
attached to a point-to-point link or to shared medium. (This is the
default setting.)
When automatic detection is selected, the switch derives the link
type from the duplex mode. A full-duplex interface is considered a
point-to-point link, while a half-duplex interface is assumed to be on
a shared link.
■
Forced True – A point-to-point connection to exactly one other
bridge.
■
Forced False – A shared connection to two or more bridges.