Brocade TurboIron 24X Series Configuration Guide - Manual (Page 612)

578 Brocade TurboIron 24X Series Configuration Guide
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802.1s Multiple Spanning Tree Protocol
NOTE
Root guard may prevent network connectivity if it is improperly configured. Root guard must be
configured on the perimeter of the network rather than the core.
NOTE
Root guard is not supported when MSTP is enabled.
Enabling STP root guard
An STP root guard is configured on an interface by entering commands similar to the following.
TurboIron(config)#interface ethernet 5
TurboIron(config-if-e10000-5)spanning-tree root-protect
Syntax: [no] spanning-tree root-protect
Enter the no form of the command to disable STP root guard on the port.
Displaying the STP root guard
To display the STP root guard state, enter the show running configuration or the show spanning-tree
root-protect command.
TurboIron#show spanning-tree root-protect
Root Protection Enabled on:
Port 1
Syntax: show spanning-tree root-protect
802.1s Multiple Spanning Tree Protocol
Multiple Spanning Tree Protocol (MSTP), as defined in IEEE 802.1s, allows multiple VLANs to be
managed by a single STP instance and supports per-VLAN STP. As a result, several VLANs can be
mapped to a reduced number of spanning-tree instances. This ensures loop-free topology for one
or more VLANs that have the similar layer-2 topology. The Brocade implementation supports up to
16 spanning tree instances in an MSTP enabled bridge which means that it can support up to 16
different Layer 2 topologies. The spanning tree algorithm used by MSTP is RSTP which provides
quick convergence.
Multiple spanning-tree regions
Using MSTP, the entire network runs a common instance of RSTP. Within that common instance,
one or more VLANs can be individually configured into distinct regions. The entire network runs the
common spanning tree instance (CST) and the regions run a local instance. The local instance is
known as Internal Spanning Tree (IST). The CST treats each instance of IST as a single bridge.
Consequently, ports are blocked to prevent loops that might occur within an IST and also
throughout the CST. With the exception of the provisions for multiple instances, MSTP operates
exactly like RSTP.