Operation Manual – MSTPH3C S3100 Series Ethernet Switches Chapter 1 MSTP Configuration1-45You can use the stp tc-protection threshold command to set the maximum times for aswitch to remove the MAC address table and ARP entries in a specific period. Whenthe number of the TC-BPDUs received within a period is less than the maximum times,the switch performs a removing operation upon receiving a TC-BPDU. After the numberof the TC-BPDUs received reaches the maximum times, the switch stops performingthe removing operation. For example, if you set the maximum times for a switch toremove the MAC address table and ARP entries to 100 and the switch receives 200TC-BPDUs in the period, the switch removes the MAC address table and ARP entriesfor only 100 times within the period.V. BPDU droppingIn a STP-enabled network, some users may send BPDU packets to the switchcontinuously in order to destroy the network. When a switch receives the BPDUpackets, it will forward them to other switches. As a result, STP calculation is performedrepeatedly, which may occupy too much CPU of the switches or cause errors in theprotocol state of the BPDU packets.In order to avoid this problem, you can enable BPDU dropping on Ethernet ports. Oncethe function is enabled on a port, the port will not receive or forward any BPDU packets.In this way, the switch is protected against the BPDU packet attacks so that the STPcalculation is assured to be right.Note:Only the S3100-EI series among S3100 series switches support the BPDU droppingfeature.1.6.2 Configuration PrerequisitesMSTP runs normally on the switch.1.6.3 Configuring BPDU GuardI. Configuration procedureTable 1-36 Configure BPDU guardOperation Command DescriptionEnter system view system-view —
