Dell Brocade DCX, Configuration Manual

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322 BigIron RX Series Configuration Guide
53-1001810-01
IEEE 802.1D Spanning Tree Protocol (STP)
12
Changing STP bridge parameters
To change a BigIron RX’s STP bridge priority to the highest value, so as to make the device the root
bridge, enter the following command.
BigIron RX(config)# vlan 20
BigIron RX(config-vlan-20)# spanning-tree priority 0
To make this change in the default VLAN, enter the following commands.
BigIron RX(config)# vlan 1
BigIron RX(config-vlan-1)# spanning-tree priority 0
Syntax: [no] spanning-tree [forward-delay <value> ] | [hello-time <value> ] | [max-age <value> ] |
[priority <value> ]
You can specify some or all of the parameters on the same command line. For information on
parameters, possible values and defaults, refer to
Table 70 on page 321.
NOTE
The hello-time <value> parameter applies only when the device or VLAN is the root bridge for its
spanning tree.
Changing STP port parameters
To change the path and priority costs for a port, enter commands such as the following.
BigIron RX(config)# vlan 10
BigIron RX(config-vlan-10)# spanning-tree ethernet 1/5 path-cost 15 priority 64
Syntax: spanning-tree ethernet <slot>/<portnum> path-cost <value> | priority <value> | disable
| enable
The ethernet <slot>/<portnum> parameter specifies the interface.
For descriptions of path cost and priority, their default and possible values, refer to Table 71 on
page 321. If you enter a priority value that is not divisible by four, the software rounds it to the
nearest value.
The disable | enable parameter disables or re-enables STP on the port. The STP state change
affects only this VLAN. The port’s STP state in other VLANs is not changed.
STP root guard
In release 02.3.00, a new security feature that allows a port to run STP but not allow the connected
device to become the Root has been added. The STP Root Guard feature provides a way to enforce
the root bridge placement in the network and trigger errors if any changes from the root bridge
placement are detected. This feature allows STP to interoperate with user network bridges while
still maintaining the bridged network topology that the administrator requires.
When Root Guard is enabled on a port, it keeps the port in designated FORWARDING state. If the
port receives a superior STP BPDU, it sets the port into BLOCKING and triggers a log message and
an SNMP trap. No further traffic will be forwarded on this port. This allows the bridge to prevent
traffic from being forwarded on ports connected to rogue or misconfigured STP bridges.