Dell Z9500 Command Reference Manual page 1782

Version
8.3.19.0
8.3.11.1
8.3.10.1
8.4.2.1
8.3.7.0
8.2.1.0
7.7.1.0
7.5.1.0
6.2.1.1
Usage
If you enable portfast bpduguard on an interface and the interface receives a
Information
BPDU, the software disables the interface and sends a message stating that fact.
The port is in ERR_DISABLE mode, yet appears in the show interface
commands as enabled. If you do not enable shutdown-on-violation, BPDUs
are still sent to the RPM CPU.
STP loop guard and root guard are supported on a port or port-channel enabled in
any Spanning Tree mode: Spanning Tree Protocol (STP), Rapid Spanning Tree
Protocol (RSTP), Multiple Spanning Tree Protocol (MSTP), and Per-VLAN Spanning
Tree Plus (PVST+).
Root guard is supported on any STP-enabled port or port-channel except when
used as a stacking port. When enabled on a port, root guard applies to all VLANs
configured on the port.
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.
Do not enable Portfast BPDU guard and loop guard at the same time on a port.
Enabling both features may result 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:
•
•
To display the type of STP guard (Portfast BPDU, root, or loop guard) enabled on a
port, enter the show spanning-tree 0 command.
1782
Description
Introduced on the S4820T.
Introduced on the Z9000.
Introduced the loopguard and rootguard options on the
S4810.
Introduced the loopguard and rootguard options on the
E-Series TeraScale, C-Series, and S-Series.
Introduced on the S4810.
Introduced the shutdown-on-violation option.
Introduced on the S-Series.
Introduced on the C-Series.
Introduced on the E-Series.
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.
Spanning Tree Protocol (STP)