Dell S3100 EMC Command Line Reference Guide for the Series 9.14.2.5 - Page 1496

Version 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 Description Introduced the loopguard and rootguard options on the S4810. Introduced the loopguard and rootguard options on the E-Series, C-Series, and SSeries. 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. Usage Information If you enable portfast bpduguard on an interface and the interface receives a 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: • 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. To display the type of STP guard (Portfast BPDU, root, or loop guard) enabled on a port, enter the show spanning-tree 0 command. 1496 Spanning Tree Protocol (STP)