Enabling MSTP
Context
MSTP must be enabled for basic MSTP functions to take effect.
Enabling MSTP immediately triggers spanning tree calculation on the network. Therefore, before enabling MSTP, perform basic configurations on switching devices to avoid network flapping, which may occur upon changes to parameters such as device priority and interface priority.
Procedure
- Run system-view
The system view is displayed.
- Run stp enable
MSTP is enabled on the switching device.
By default, the MSTP function is enabled on the device.After MSTP is enabled on a port, edge port detection is started automatically. If the port fails to receive BPDU packets within (2 x Hello Timer + 1) seconds, the port is set to an edge port. Otherwise, the port is set to a non-edge port.
- Run commit
The configuration is committed.
Follow-up Procedure
If the topology of a spanning tree changes, the forwarding paths to associated VLANs are changed. On the switching device, therefore, the ARP entries corresponding to these VLANs need to be updated. MSTP processes ARP entries in either fast or normal mode.
In fast mode, ARP entries to be updated are directly deleted.
In normal mode, ARP entries to be updated are rapidly aged.
The remaining lifetime of ARP entries to be updated is set to 0. The switching device rapidly processes these aged entries. If the number of ARP aging probe attempts is not set to 0, ARP implements aging probe for these ARP entries.
To specify which mode is used for STP/RSTP convergence, run the stp converge { fast | normal } command in the system view.
By default, the normal MSTP convergence mode is used. If fast mode is used, ARP entries are frequently deleted. This causes high CPU usage on the device (reaching 100%) and results in frequent network flapping. Therefore, using normal mode is recommended.