Dell PowerConnect B-RX Configuration Manual page 395

Root Guard should be configured on all ports where the root bridge should not appear. In this way,
the core bridged network can be cut off from the user network by establishing a protective
perimeter around it.
Once the port stops receiving superior BPDUs, root protect will automatically set the port back to a
FORWARDING state after the timeout period has expired.
NOTE
Root Guard may prevent network connectivity if improperly configured. It needs to be configured on
the perimeter of the network rather than the core.
Enabling STP root guard
A STP Root Guard is configured on a per interfaces basis. To enable a Root Guard, enter a
command such as the following.
BigIron RX (config)#interface ethernet 5/5
BigIron RX(config-if-e10000-5/5)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.
Setting the STP root guard timeout period
To configure the STP Root protect timeout period globally, enter a command such as the following.
BigIron RX(config)# spanning-tree root-protect timeout 120
Syntax: spanning-tree root-protect timeout <timeout in seconds>
The timeout in seconds parameter allows you to set the timeout period. The timeout period may be
configured to anything between 5 and 600 seconds. Default is 30 seconds.
Displaying the STP root guard
To display the STP Root Guard state, enter the show spanning-tree root-protect command.
BigIron RX#show spanning-tree root-protect
Port VLAN Current State
13/6 3 Consistent state
13/9 2 Inconsistent state (29 seconds left on timer)
Syntax: show spanning-tree root-protect
Sample Syslog messages
A Syslog message such as the following is generated after the Root Guard blocks a port.
STP: Root Guard Port 12/21, VLAN 10 inconsistent (Received superior BPDU)
A Syslog message such as the following is generated after the Root Guard unblocks a port.
STP: Root Guard Port 12/21, VLAN 10 consistent (Timeout)
BigIron RX Series Configuration Guide
53-1001810-01
IEEE 802.1D Spanning Tree Protocol (STP)
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