97
•
RSTP mode
—All ports of the device send RSTP BPDUs. A port in this mode automatically transits to
the STP mode when it receives STP BPDUs from the peer device. A port in this mode does not transit
to the MSTP mode when it receives MSTP BPDUs from the peer device.
•
MSTP mode
—All ports of the device send MSTP BPDUs. A port in this mode automatically transits
to the STP mode when receiving STP BPDUs from the peer device. A port in this mode does not
transit to the RSTP mode when receiving RSTP BPDUs from the peer device.
•
PVST mode
—All ports of the device send PVST BPDUs. Each VLAN maintains a spanning tree. In a
network, the amount of spanning trees maintained by all devices equals the number of
PVST-enabled VLANs multiplied by the number of PVST-enabled ports. If the amount of spanning
trees exceeds the capacity of the network, device CPUs will be overloaded. Packet forwarding is
interrupted, and the network becomes unstable. The number of spanning trees that a device can
maintain is 144.
The MSTP mode is compatible with the RSTP mode, and the RSTP mode is compatible with the STP mode.
Compatibility of the PVST mode depends on the link type of a port:
•
On an access port, the PVST mode is compatible with other spanning tree modes in all VLANs.
•
On a trunk port or hybrid port, the PVST mode is compatible with other spanning tree modes only
in VLAN 1.
Configuration restrictions and guidelines
When you make configurations in different spanning tree modes, follow these guidelines:
•
In STP or RSTP mode, do not specify an MSTI or VLAN. Otherwise, the spanning tree configuration
does not take effect.
•
In PVST mode, if you specify a VLAN, the spanning tree configuration takes effect on the specified
VLAN. Otherwise, the spanning tree configuration does not take effect.
•
In MSTP mode, if you specify an MSTI, the spanning tree configuration takes effect on the specified
MSTI. If you specify a VLAN, the spanning tree configuration does not take effect. If you do not
specify any MSTI or VLAN, the spanning tree configuration takes effect on the CIST.
Configuration procedure
To set the spanning tree mode:
Step Command Remarks
1.
Enter system view.
system-view
N/A
2.
Set the spanning tree mode.
stp mode
{
mstp
|
pvst
|
rstp
|
stp
}
The default setting is the
MSTP mode.
Configuring an MST region
Spanning tree devices belong to the same MST region only if they are both connected through a physical
link and both configured with the following details:
•
Format selector (0 by default, not configurable).
•
MST region name.