Configuration Guide User guide

FastIron Configuration Guide 1157
53-1002494-02
PVST/PVST+ compatibility
Brocade(config)#stp-group 1
Brocade(config-stp-group-1)#master-vlan 1
Brocade(config-stp-group-1)#member-group 1
Brocade(config-stp-group-1)#member-vlan 4001 4004 to 4010
Brocade(config-stp-group-1)#stp-group 2
Brocade(config-stp-group-2)#master-vlan 201
Brocade(config-stp-group-2)#member-group 2
Brocade(config-stp-group-2)#member-vlan 4002 4003 4011 to 4015
Brocade(config-stp-group-2)#stp-group 3
Brocade(config-stp-group-3)#master-vlan 401
Brocade(config-stp-group-3)#member-group 3
...
Brocade(config-stp-group-19)#stp-group 20
Brocade(config-stp-group-20)#master-vlan 3081
Brocade(config-stp-group-20)#member-group 20
PVST/PVST+ compatibility
The FastIron family of switches support Cisco's Per VLAN Spanning Tree plus (PVST+), by allowing
the device to run multiple spanning trees (MSTP) while also interoperating with IEEE 802.1Q
devices
1
.
NOTE
Brocade ports automatically detect PVST+ BPDUs and enable support for the BPDUs once detected.
You do not need to perform any configuration steps to enable PVST+ support. However, to support
the IEEE 802.1Q BPDUs, you might need to enable dual-mode support.
Support for Cisco's Per VLAN Spanning Tree plus (PVST+), allows a Brocade device to run multiple
spanning trees (MSTP) while also interoperating with IEEE 802.1Q devices. Brocade ports
automatically detect PVST+ BPDUs and enable support for the BPDUs once detected. The
enhancement allows a port that is in PVST+ compatibility mode due to auto-detection to revert to
the default MSTP mode when one of the following events occurs:
• The link is disconnected or broken
• The link is administratively disabled
• The link is disabled by interaction with the link-keepalive protocol
This enhancement allows a port that was originally interoperating with PVST+ to revert to MSTP
when connected to a Brocade device.
Overview of PVST and PVST+
Per VLAN Spanning Tree (PVST) is a Cisco proprietary protocol that allows a Cisco device to have
multiple spanning trees. The Cisco device can interoperate with spanning trees on other PVST
devices but cannot interoperate with IEEE 802.1Q devices. An IEEE 802.1Q device has all its ports
running a single spanning tree. PVST+ is an extension of PVST that allows a Cisco device to also
interoperate with devices that are running a single spanning tree (IEEE 802.1Q).
Enhanced PVST+ support allows a Brocade device to interoperate with PVST spanning trees and
the IEEE 802.1Q spanning tree at the same time.
1. Cisco user documentation for PVST/PVST+ refers to the IEEE 802.1Q spanning tree as the
Common Spanning Tree (CST).