Cisco Systems N3KC3064TFAL3 manual Configuring MST, MST Configuration Guidelines, Enabling MST

Configuring Multiple Spanning Tree

Interoperability with Rapid PVST+: Understanding PVST Simulation

Interoperability with Rapid PVST+: Understanding PVST Simulation

MST interoperates with Rapid PVST+ with no need for user configuration. The PVST simulation feature enables this seamless interoperability.

Note PVST simulation is enabled by default. That is, by default, all interfaces on the switch interoperate between MST and Rapid PVST+.

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 Rapid PVST+ simulation, which can be done per port or globally for the entire switch, moves the MST-enabled port to the 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 Rapid PVST+/SSTP BPDUs, and then the port resumes the normal STP transition process.

Configuring MST

MST Configuration Guidelines

When configuring MST, follow these guidelines:

•When you work with private VLANs, enter the private-vlan synchronize command to map the secondary VLANs to the same MST instance as the primary VLAN.

•When you are in the MST configuration mode, the following guidelines apply:

◦Each command reference line creates its pending regional configuration.

◦The pending region configuration starts with the current region configuration.

◦To leave the MST configuration mode without committing any changes, enter the abort command.

◦To leave the MST configuration mode and commit all the changes that you made before you left the mode, enter the exit command.

Enabling MST

You must enable MST; Rapid PVST+ is the default.

Caution Changing the spanning tree mode disrupts traffic because all spanning tree instances are stopped for the previous mode and started for the new mode.

Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)

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