Cisco Catalyst 2960 Series, Configuration Manual

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Default Setting Feature
32768 Switch priority (configurable on a per-CIST port basis)
128 Spanning-tree port priority (configurable on a per-CIST port
basis)
1000 Mb/s: 20000
100 Mb/s: 20000
10 Mb/s: 20000
1000 Mb/s: 20000
100 Mb/s: 20000
10 Mb/s: 20000
Spanning-tree port cost (configurable on a per-CIST port basis)
3 seconds Hello time
20 seconds Forward-delay time
20 seconds Maximum-aging time
20 hops Maximum hop count
Related Topics
Supported Spanning-Tree Instances, on page 221
Specifying the MST Region Configuration and Enabling MSTP , on page 261
About MST-to-PVST+ Interoperability (PVST+ Simulation)
The PVST+ simulation feature enables seamless interoperability between MST and Rapid PVST+. You can
enable or disable this per port, or globally. PVST+ simulation is enabled by default.
However, you may want to control the connection between MST and Rapid PVST+ to protect against
accidentally connecting an MST-enabled port to a Rapid PVST+-enabled port. Because Rapid PVST+ is the
default STP mode, you may encounter many Rapid PVST+-enabled connections.
Disabling this feature causes the switch to stop the MST region from interacting with PVST+ regions. The
MST-enabled port moves to a PVST peer inconsistent (blocking) state once it detects it is connected to a
Rapid PVST+-enabled port. This port remains in the inconsistent state until the port stops receiving Shared
Spanning Tree Protocol (SSTP) BPDUs, and then the port resumes the normal STP transition process.
You can for instance, disable PVST+ simulation, to prevent an incorrectly configured switch from connecting
to a network where the STP mode is not MSTP (the default mode is PVST+).
Observe these guidelines when you configure MST switches (in the same region) to interact with PVST+
switches:
• Configure the root for all VLANs inside the MST region as shown in this example:
Switch#
show spanning-tree mst interface gigabitethernet 1/1
GigabitEthernet1/1 of MST00 is root forwarding
Consolidated Platform Configuration Guide, Cisco IOS Release 15.2(4)E (Catalyst 2960-X Switches)
258
Information About MSTP