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Usage
Information
Example
1274
|
Rapid Spanning Tree Protocol (RSTP)
The BPDU guard option prevents the port from participating in an active STP topology in case a
BPDU appears on a port unintentionally, 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, will immediately transition to
the forwarding state. Only ports connected to end-hosts should be configured as edge ports.
Consider an edge port similar to a port with a spanning-tree portfast enabled.
If shutdown-on-violation is not enabled, BPDUs will still be sent to the RPM CPU.
STP root guard and loop guard cannot be enabled 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
is displayed:
% 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.
Figure 50-7. spanning-tree rstp edge-port Command
FTOS(conf)#interface gigabitethernet 4/0
FTOS(conf-if-gi-4/0)#spanning-tree rstp edge-port
FTOS(conf-if-gi-4/0)#show config
!
interface GigabitEthernet 4/0
no ip address
switchport
spanning-tree rstp edge-port
no shutdown
FTOS#
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