Spanning Tree Protocol
Configuring STP Status and Global Settings
Cisco 220 Series Smart Switches Administration Guide Release 1.1.0.x 148
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The switch supports the following STP modes:
• Classic STP—Provides a single path between any two end stations,
avoiding and eliminating loops.
• Rapid STP (RSTP)—Detects network topologies to provide faster
convergence of the spanning tree. This is most effective when the network
topology is naturally tree-structured, and therefore faster convergence
might be possible. RSTP is enabled by default.
• Multiple STP (MSTP)—MSTP is based on RSTP. It detects Layer 2 loops,
and attempts to mitigate them by preventing the involved port from
transmitting traffic. Since loops exist on a per-Layer 2-domain basis, a
situation can occur where there is a loop in VLAN A and no loop in VLAN B. If
both VLANs are on Port X, and STP wants to mitigate the loop, it stops traffic
on the entire port, including VLAN B traffic.
MSTP solves this problem by enabling several STP instances, so that it is
possible to detect and mitigate loops separately in each instance. By
associating instances to VLANs, each instance is associated with the Layer
2 domain on which it performs loop detection and mitigation. This enables a
port to be stopped in one instance, such as traffic from VLAN A that is
causing a loop, while traffic can remain active in another domain where no
loop was seen, such as on VLAN B.
Configuring STP Status and Global Settings
Use the STP Status and Global Settings page to enable STP, RSTP, or MSTP on the
switch.
Use the STP Interface Settings page, RSTP Interface Settings page, and MSTP
Properties page to configure each mode, respectively.
To set STP status and global settings:
STEP 1 Click Spanning Tree > STP Status and Global Settings.
STEP 2 In the Global Settings area, enter the following information:
• Spanning Tree State—Enable or disable STP on the switch.
• STP Loopback Guard—Select to enable Loopback Guard on the device.
• STP Operation Mode—Select the STP mode.
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