62NOTE:• 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.• Among loop guard, root guard and edge port settings, only one function (whichever is configured theearliest) 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 routerflushes its forwarding address entries. If someone forges TC-BPDUs to attack the router, the router 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 router can perform every a certain period of time (10 seconds). For TC-BPDUsreceived in excess of the limit, the router performs forwarding address entry flush when the time periodexpires. This prevents frequent flushing of forwarding address entries.To enable TC-BPDU guard:Step Command Remarks1. Enter system view. system-view N/A2. Enable the TC-BPDU guard function. stp tc-protection enableOptional.By default, TC-BPDU guard isenabled.3. Configure the maximum number offorwarding address entry flushes that therouter can perform every 10 seconds.stp tc-protection thresholdnumberOptional.The default setting is 6.NOTE:H3C does not recommend you disable this feature.Displaying and maintaining the spanning treeTask Command RemarksDisplay information about ports blockedby spanning tree protection functions.display stp abnormal-port [ | { begin |exclude | include } regular-expression ] Available in any viewDisplay BPDU statistics on ports.display stp bpdu-statistics [ interfaceinterface-type interface-number [ instanceinstance-id ] ] [ | { begin | exclude |include } regular-expression ]Available in any viewDisplay information about ports shutdown by spanning tree protectionfunctions.display stp down-port [ | { begin |exclude | include } regular-expression ] Available in any viewDisplay the historical information of portrole calculation for the specified MSTI orall MSTIs.display stp [ instance instance-id ] history[ slot slot-number ] [ | { begin | exclude |include } regular-expression ]Available in any view
