Usage
Information
The
BPDU guard
option prevents the port from participating in an active STP
topology in case a BPDU appears on a port unintentionally, or is misconfigured, or
is subject to a DOS attack. This option places the port into an Error Disable state if a
BPDU appears and a message is logged so that the administrator can take
corrective action.
NOTE: A port configured as an edge port, on an RSTP switch, immediately
transitions to the Forwarding state. Only configure ports connected to end-
hosts as edge ports. Consider an edge port similar to a port with a
spanning-
tree portfast
enabled.
If you do not enable
shutdown-on-violation
, BPDUs are still sent to the RPM
CPU.
You cannot enable STP root guard and loop guard at the same time on a port. For
example, if you configure loop guard on a port on which root guard is already
configured, the following error message displays:
% Error: RootGuard is
configured. Cannot configure LoopGuard
.
Enabling Portfast BPDU guard and loop guard at the same time on a port results in
a port that remains in a Blocking state and prevents traffic from flowing through it.
For example, when Portfast BPDU guard and loop guard are both configured:
• If a BPDU is received from a remote device, BPDU guard places the port in an
Err-Disabled Blocking state and no traffic is forwarded on the port.
• If no BPDU is received from a remote device, loop guard places the port in a
Loop-Inconsistent Blocking state and no traffic is forwarded on the port.
Example
Dell(conf)#interface gigabitethernet 4/0
Dell(conf-if-gi-4/0)#spanning-tree rstp edge-port
Dell(conf-if-gi-4/0)#show config
!
interface GigabitEthernet 4/0
no ip address
switchport
spanning-tree rstp edge-port
no shutdown
Dell#
spanning-tree rstp
Configure an RSTP interface with one of these settings: port cost, edge port with optional bridge port
data unit (BPDU) guard, port priority, loop guard, or root guard.
Syntax
spanning-tree rstp {cost
port-cost
| edge-port [bpduguard
[shutdown-on-violation]] | bpdufilter | priority
priority
|
{rootguard}}
Parameters
cost
port-cost
Enter the keyword
cost
then the port cost value. The range
is from 1 to 200000. The defaults are:
Rapid Spanning Tree Protocol (RSTP)
1149
