Enabling MSTP
Context
Enabling MSTP on a ring network immediately triggers spanning tree calculation. If basic configurations are not performed on switches and interfaces before MSTP is enabled, network flapping may occur upon changes to parameters such as device priority and interface priority
Procedure
- Run:
system-viewThe system view is displayed.
- Run:
stp enableMSTP is enabled on the switch.
By default, the MSTP function is enabled on the device.
If the management network interface for an MSTP-enabled device is a VLANIF interface of a VLAN, run the ethernet-loop-protection ignored-vlan command to specify this VLAN as an ignored VLAN. During MSTP calculation, the interface on which the ignored VLAN is configured remains in forwarding state. Therefore, services are not interrupted.
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.
Follow-up Procedure
If the topology of a spanning tree changes, the forwarding paths to associated VLANs are changed. On the switch, 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 switch 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.