Users Guide

• root — Set the guard type to root.
• none — Set the guard type to none.
Port enabled with loop guard conditions
• Loop guard is supported on any STP-enabled port or port-channel interface in RPVST+ mode.
• You cannot enable root guard and loop guard at the same time on an STP port. The loop guard conguration overwrites an
existing root guard conguration and vice versa.
• Enabling BPDU guard and loop guard at the same time on a port results in a port that remains blocking and prevents trac from
owing through it. For example, when you congure both Portfast BPDU guard and loop guard:
– If a BPDU is received from a remote device, BPDU guard places the port in the Err-Disabled Blocking state and no trac
forwards on the port.
– If no BPDU is received from a remote device which was sending BPDUs, loop guard places the port in the Loop-Inconsistent
Blocking state and no trac forwards on the port.
• When used in a PVST+ network, STP loop guard performs per-port or per port-channel at a VLAN level. If no BPDUs are received
on a port-channel interface, the port or port-channel transitions to a Loop-Inconsistent or Blocking state only for this VLAN.
BPDU lter
OS10(conf-if-eth1/1/4)# spanning-tree bpdufilter enable
OS10(conf-if-eth1/1/4)# do show spanning-tree interface ethernet 1/1/4
ethernet1/1/4 of vlan1 is designated Blocking
Edge port:no (default) port guard :none (default)
Link type is point-to-point (auto)
Boundary: NO bpdu filter : Enable bpdu guard : bpduguard shutdown-on-
violation :disable RootGuard: enable LoopGuard disable
Bpdus (MRecords) sent 134, received 138
Interface Designated
Name PortID Prio Cost Sts Cost Bridge ID PortID
--------------------------------------------------------------------------
ethernet1/1/4 128.272 128 500 BLK 500 32769 90b1.1cf4.a911 128.272
BPDU guard
OS10(config)# interface ethernet 1/1/4
OS10(conf-if-eth1/1/4)# spanning-tree bpduguard enable
OS10(conf-if-eth1/1/4)# do show spanning-tree interface ethernet 1/1/4
ethernet1/1/4 of vlan1 is designated Blocking
Edge port:no (default) port guard :none (default)
Link type is point-to-point (auto)
Boundary: NO bpdu filter : Enable bpdu guard : bpduguard shutdown-on-
violation :enable RootGuard: enable LoopGuard disable
Bpdus (MRecords) sent 134, received 138
Interface Designated
Name PortID Prio Cost Sts Cost Bridge ID PortID
------------------------------------------------------------------
ethernet1/1/4 128.272 128 500 BLK 500 32769 90b1.1cf4.a911 128.272
Loop guard
OS10(config)# interface ethernet 1/1/4
OS10(conf-if-eth1/1/4)# spanning-tree guard loop
OS10(conf-if-eth1/1/4)# do show spanning-tree interface ethernet 1/1/4
ethernet1/1/4 of vlan1 is root Forwarding
Edge port:no (default) port guard :none (default)
Link type is point-to-point (auto)
Boundary: NO bpdu filter : bpdu guard : bpduguard shutdown-on-
violation :disable RootGuard: disable LoopGuard enable
Bpdus (MRecords) sent 7, received 20
Interface Designated
Name PortID Prio Cost Sts Cost Bridge ID PortID
-------------------------------------------------------------------------
ethernet1/1/4 128.272 128 500 FWD 0 32769 90b1.1cf4.9d3b 128.272
Root guard
OS10(conf-if-eth1/1/4)# spanning-tree guard root
OS10(conf-if-eth1/1/4)# do show spanning-tree interface ethernet 1/1/4
396
Layer 2