Users Guide

Table Of Contents
Spanning Tree Protocol 839
STP-PV is the IEEE 802.1s (STP) standard implemented per VLAN. The
STP-PV-related state machine, roles, and timers are similar to those defined
for STP. STP-PV does not have the DirectLink Rapid Convergence (DRC) or
IndirectLink Rapid Convergence (IRC) features enabled by default. These
features can be enabled by the switch administrator. STP-PV/RSTP-PV are
not compatible with protocol-based VLANs . Ensure that ports enabled for
per-VLAN spanning tree are not configured for protocol-based VLAN
capability.
The switch spanning tree configuration is global in nature. Enabling RSTP-
PV disables other spanning tree modes on the switch. The switch cannot
operate with some ports configured to operate in standard spanning tree
mode and others to operate in RSTP-PV mode. However, RSTP-PV has
fallback modes for compatibility with standards-based versions of spanning
tree.
Access Ports—For an access port, normal IEEE BPDUs will be received and
sent, though STP-PV or RSTP-PV is enabled on the switch. BPDUs received
on the access port will be associated with the CST instance.
Trunk Ports—If the native VLAN on an IEEE 802.1Q trunk is VLAN 1:
VLAN 1 STP BPDUs are sent to the IEEE STP MAC address
(0180.c200.0000), untagged.
VLAN 1 STP BPDUs are also sent to the SSTP MAC address, untagged.
Non-VLAN 1 STP BPDUs are sent to the SSTP MAC address (also called
the Shared Spanning Tree Protocol [SSTP] MAC address, 0100.0ccc.cccd),
tagged with a corresponding IEEE 802.1Q VLAN tag.
If the native VLAN on an IEEE 802.1Q trunk is not VLAN 1:
VLAN 1 STP BPDUs are sent to the SSTP MAC address, tagged with a
corresponding IEEE 802.1Q VLAN tag.
VLAN 1 STP BPDUs are also sent to the IEEE STP MAC address on the
Native VLAN of the IEEE 802.1Q trunk, untagged.
Non-VLAN 1 STP BPDUs are sent to the SSTP MAC address, tagged with
a corresponding IEEE 802.1Q VLAN tag.