Brocade FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide - Manual (Page 327)

Displaying the STP root guard
To display the STP root guard state, enter the show running configuration or the show span root-
protect command.
device#show span root-protect
Root Protection Enabled on:
Port 1
Syntax: show span root-protect
Displaying the root guard by VLAN
You can display root guard information for all VLANs or for a specific VLAN. For example, to display
root guard violation information for VLAN 7.
Syntax: show spanning-tree [vlan-id]
If you do not specify a vlan-id , information for all VLANs is displayed. For example, to display root
guard violation information for VLAN 7.
device#show spanning-tree vlan 7
STP instance owned by VLAN 7
Global STP (IEEE 802.1D) Parameters:
VLAN Root Root Root Prio Max He- Ho- Fwd Last Chg Bridge
ID ID Cost Port rity Age llo ld dly Chang cnt Address
Hex sec sec sec sec sec
7 a000000011112220 0 Root a000 20 2 1 15 4 4 000011112220
Port STP Parameters:
Port Prio Path State Fwd Design Designated Designated
Num rity Cost Trans Cost Root Bridge
Hex
1 80 19 ROOT-INCONS 2 0 a000000011112220 a000000011112220
Designated Protection
Designated Protection ensures that a port cannot go to the designated forwarding state in STP 802.1d
or 802.1w. For example, a fast uplink port should never become a designated port to avoid loops in a
network topology. It should either be a root port in any STP state or a non-root port in a blocking state.
You can enable Designated Protection on the port to ensure that it does not go to the designated
forwarding state. If STP tries to put this port into the designated forwarding state, the device puts this
port into a designated inconsistent STP state. This is effectively equivalent to the listening state in STP
in which a port cannot transfer any user traffic. When STP no longer marks this port as a designated
port, the port is automatically removed from the designated inconsistent state.
Designation Protection is a port-level feature, while the designated inconsistent state is a per-STP-
instance, per-port state. In PVST, a port can belong to several VLANs where each VLAN runs a
separate spanning tree instance. The designated inconsistent state in one spanning tree instance does
not affect the traffic in other spanning tree instances.
For example, consider an interface eth 1 that is in VLAN 20 and VLAN 50. VLAN 20 runs one instance
of STP and VLAN 50 runs another instance. Interface eth1 can be in the designated inconsistent state
for VLAN 50 and block the VLAN 50 traffic while it is in root forwarding state for VLAN 20 and allow
VLAN 20 traffic.
You can view the status of the Designated Protection feature on a port with the show interface
ethernet command for that port.
Displaying the STP root guard
FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide 327
53-1003086-04