1-38z Do not enable loop guard on a port connecting user terminals. Otherwise, the port will stay in thediscarding state in all MSTIs because it cannot receive BPDUs.z Among loop guard, root guard and edge port settings, only one function (whichever is configuredthe earliest) can take effect on a port at the same time.Enabling TC-BPDU guardWhen receiving topology change (TC) BPDUs (the BPDUs used to notify topology changes), a switchflushes its forwarding address entries. If someone forges TC-BPDUs to attack the switch, the switch willreceive a large number of TC-BPDUs within a short time and be busy with forwarding address entryflushing. This affects network stability.With the TC-BPDU guard function, you can set the maximum number of immediate forwarding addressentry flushes that the switch can perform within a certain period of time after receiving the first TC-BPDU.For TC-BPDUs received in excess of the limit, the switch performs forwarding address entry flush onlywhen the time period expires. This prevents frequent flushing of forwarding address entries.Follow these steps to enable TC-BPDU guard:To do... Use the command... RemarksEnter system view system-view —Enable the TC-BPDU guard function stp tc-protection enable OptionalEnabled by defaultConfigure the maximum number offorwarding address entry flushes that thedevice can perform within a specific timeperiod after it receives the first TC-BPDUstp tc-protectionthreshold numberOptional6 by defaultIt is not recommended to disable this feature.Displaying and Maintaining MSTPTo do... Use the command... RemarksView information aboutabnormally blocked ports display stp abnormal-port Available in any viewView information about portsblocked by STP protectionfunctionsdisplay stp down-port Available in any viewView the historical information ofport role calculation for thespecified MSTI or all MSTIsdisplay stp [ instance instance-id ]history Available in any view
