Configuration Guide User guide

BigIron RX Series Configuration Guide 327
53-1002484-04
Chapter
12
Configuring Spanning Tree Protocol
In this chapter
•IEEE 802.1D Spanning Tree Protocol (STP) . . . . . . . . . . . . . . . . . . . . . . . . . 327
•IEEE Single Spanning Tree (SSTP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
•PVST/PVST+ compatibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
•SuperSpan™ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
IEEE 802.1D Spanning Tree Protocol (STP)
The BigIron RX supports Spanning Tree Protocol (STP) as described in the IEEE 802.10-1998
specification. STP eliminates Layer 2 loops in networks, by selectively blocking some ports and
allowing other ports to forward traffic, based on configurable bridge and port parameters. STP
also ensures that the least cost path is taken when multiple paths exist between ports or VLANs. If
the selected path fails, STP searches for and then establishes an alternate path to prevent or limit
retransmission of data.
NOTE
The total number of supported STP, RSTP, or MSTP indices is 128.
Enabling or disabling STP
STP is disabled by default on the device. Thus, new VLANs you configure on the device have STP
disabled by default. Table 74 lists the default STP states for the device.
By default, each VLAN on a BigIron RX runs a separate spanning tree instance. Each device has
one VLAN (VLAN 1) by default that contains all of its ports. However, if you configure additional
port-based VLANs on a device, then each of those VLANs on which STP is enabled and VLAN 1 all
run separate spanning trees.
You can enable or disable STP on the following levels:
• Globally – Affects all VLANs on the device.
TABLE 74 Default STP states
Device type Default STP type Default STP state Default STP state of new
VLANs
BigIron RX Brocade’s multiple instances of
spanning tree
Disabled Disabled