FUJITSU PSWITCH User’s Guide
74 December/2018
3.1.2.8.12. PVRSTP and PVSTP
PVRSTP is the IEEE 802.1w (RSTP) standard implemented per VLAN. A single
instance of rapid spanning tree (RSTP) runs on each configured VLAN. Each RSTP
instance on a VLAN has a root switch. PVSTP is the IEEE 802.1D (STP) standard
implemented per VLAN.
In other words, with PVSTP/PVRSTP, each configured VLAN runs an independent
instance of PVST/PRVST. Each PVSTP/PVRSTP instance elects a root bridge
independent of the other. This means there are as many root bridges in the region
as there are VLANs configured for PVSTP/PVRSTP.
The difference between STP and PVSTP/PVRSTP is primarily in the way the protocol
maps spanning tree instances to VLANs: PVSTP/PVRSTP creates a spanning tree
instance for every VLAN, whereas STP maps all VLANs to one instance.
PVSTP is equivalent to the Cisco PVST+ protocol, and the two protocols can
interoperate. Similarly, PVRSTP is equivalent to Cisco's RPVST+, and these two
protocols can interoperate.
Enabling PVSTP or PVRSTP on a switch disables other spanning tree modes on the
switch.
The switch running PVSTP/PVRSTP transmits IEEE spanning tree BPDUs along with
SSTP BPDUs. The SSTP BPDUs are transmitted as untagged packets on an access or
native VLAN and transmitted as tagged packets on other VLANs.
If the switch running PVSTP/PVRSTP receives an IEEE spanning tree BPDU, then the
switch will include the BPDU in an access VLAN or native VLAN instance.
PVSTP/PVRSTP behavior is as follows:
Access Ports — If the port is configured as access port, then the port sends IEEE
spanning tree BPDUs. For an access port, normal IEEE BPDUs will be received and
sent, though PVSTP or PVRSTP is enabled on the switch. BPDUs received on the
access port will be associated with the CST instance.
Trunk Ports —If the port is configured as a trunk port, then the port sends IEEE
spanning tree BPDUs and SSTP BPDUs on the native VLAN. For other VLANs, the
port transmits SSTP BPDUs as tagged packets with the respective VLANs. If the
trunk port receives IEEE spanning tree BPDUs, then the received BPDUs are
consumed and processed by the instance that is mapped to the native VLAN. The
SSTP BPDUs are processed by instances to which the respective VLANs are mapped.
If the native VLAN on an IEEE 802.1Q trunk is VLAN 1:
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