9-102
Configuring Advanced Features
Spanning Tree Protocol (STP)
Configuring Advanced
Features
Spanning Tree Protocol (STP)
STP Features
The switch uses the IEEE 802.1D Spanning Tree Protocol (STP), when
enabled, to ensure that only one path at a time is active between any two nodes
on the network. In networks where there is more than one physical path
between any two nodes, STP ensures a single active path between them by
blocking all redundant paths. Enabling STP is necessary in such networks
because having more than one path between a pair of nodes causes loops in
the network, which can result in duplication of messages, leading to a “broad-
cast storm” that can bring down the network.
Note You should enable STP in any switch that is part of a redundant physical link
(loop topology). (It is recommended that you enable STP on all switches
belonging to a loop topology.) This topic is covered in more detail under “How
STP Operates” on page 9-108.
As recommended in the IEEE 802.1Q VLAN standard, the Switches 2512 and
2524 use single-instance STP; a single spanning tree is created to make sure
there are no network loops associated with any of the connections to the
switch, regardless of whether VLANs are configured on the switch. Thus, these
switches do not distinguish between VLANs when identifying redundant
physical links. If VLANs are configured on the switch, see “STP Operation with
802.1Q VLANs” on page 9-110.
Feature Default Menu CLI Web
viewing the STP configuration n/a page
9-103
page
9-105
—
enable/disable STP disabled page
9-103
page
9-106
page
9-108
reconfiguring general operation priority: 32768
max age: 20 s
hello time: 2 s
fwd. delay: 15 s
page
9-103
page
9-106
reconfiguring per-port STP path cost: var
priority: 128
mode: norm
page
9-103
page
9-107
monitoring STP n/a page
10-15
page
10-15
n/a
