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Loop Protect, Root Protect, TC Protect, BPDU Protect

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 Loop Protect In a stable network, a switch maintains the states of ports by receiving and processing BPDU packets from the upstream switch. However, when link congestions or link failures occurred to the network, a down stream switch does not receive BPDU packets for certain period, which results in spanning trees being regenerated and roles of ports being reselected, and causes the blocked ports to transit to forwarding state. Therefore, loops may be incurred in the network. The loop protect function can suppresses loops. With this function enabled, a port, regardless of the role it plays in instances, is always set to blocking state, when the port does not receive BPDU packets from the upstream switch and spanning trees are regenerated, and thereby loops can be prevented.  Root Protect A CIST and its secondary root bridges are usually located in the high-bandwidth core region. Wrong configuration or malicious attacks may result in configuration BPDU packets with higher priorities being received by the legal root bridge, which causes the current legal root bridge to lose its position and network topology jitter to occur. In this case, flows that should travel along high-speed links may lead to low-speed links, and network congestion may occur. To avoid this, MSTP provides root protect function. Ports with this function enabled can only be set as designated ports in all spanning tree instances. When a port of this type receives BDPU packets with higher priority, it transits its state to blocking state and stops forwarding packets (as if it is disconnected from the link). The port resumes the normal state if it does not receive any configuration BPDU packets with higher priorities for a period of two times of forward delay.  TC Protect A switch removes MAC address entries upon receiving TC-BPDU packets. If a user maliciously sends a large amount of TC-BPDU packets to a switch in a short period, the switch will be busy with removing MAC address entries, which may decrease the performance and stability of the network. To prevent the switch from frequently removing MAC address entries, you can enable the TC protect function on the switch. With TC protect function enabled, if the account number of the received TC-BPDUs exceeds the maximum number you set in the TC threshold field, the switch will not performs the removing operation in the TC protect cycle. Such a mechanism prevents the switch from frequently removing MAC address entries.  BPDU Protect Ports of the switch directly connected to PCs or servers are configured as edge ports to rapidly transit their states. When these ports receive BPDUs, the system automatically configures these ports as non-edge ports and regenerates spanning trees, which may cause network topology jitter. Normally these ports do not receive BPDUs, but if a user maliciously attacks the switch by sending BPDUs, network topology jitter occurs. To prevent this attack, MSTP provides BPDU protect function. With this function enabled on the switch, the switch shuts down the edge ports that receive BPDUs and reports these cases to the administrator. If a port is shut down, only the administrator can restore it. 84

Section	Page
Package Contents	11
Chapter 1 About this Guide	12
1.1 Intended Readers	12
1.2 Conventions	12
1.3 Overview of This Guide	12
Chapter 2 Introduction	17
2.1 Overview of the Switch	17
2.2 Appearance Description	17
2.2.1 Front Panel	17
2.2.2 Rear Panel	21
Chapter 3 Login to the Switch	24
3.1 Login	24
3.2 Configuration	24
Chapter 4 System	26
4.1 System Info	26
4.1.1 System Summary	26
4.1.2 Device Description	27
4.1.3 System Time	28
4.1.4 Daylight Saving Time	29
4.1.5 System IP	30
4.2 User Management	32
4.2.1 User Table	32
4.2.2 User Config	32
4.3 System Tools	34
4.3.1 Boot Config	34
4.3.2 Config Restore	34
4.3.3 Config Backup	35
4.3.4 Firmware Upgrade	36
4.3.5 System Reboot	36
4.3.6 System Reset	37
4.4 Access Security	37
4.4.1 Access Control	37
4.4.2 HTTP Config	38
4.4.3 HTTPS Config	39
4.4.4 SSH Config	43
4.4.5 Telnet Config	49
Chapter 5 Switching	50
5.1 Port	50
5.1.1 Port Config	50
5.1.2 Port Mirror	51
5.1.3 Port Security	53
5.1.4 Port Isolation	55
5.1.5 Loopback Detection	56
5.2 LAG	58
5.2.1 LAG Table	58
5.2.2 Static LAG	60
5.2.3 LACP Config	61
5.3 Traffic Monitor	62
5.3.1 Traffic Summary	62
5.3.2 Traffic Statistics	63
5.4 MAC Address	65
5.4.1 Address Table	66
5.4.2 Static Address	68
5.4.3 Dynamic Address	69
5.4.4 Filtering Address	71
Chapter 6 VLAN	73
6.1 802.1Q VLAN	74
6.1.1 VLAN Config	75
6.1.2 Port Config	77
6.2 Application Example for 802.1Q VLAN	78
Chapter 7 Spanning Tree	80
7.1 STP Config	85
7.1.1 STP Config	85
7.1.2 STP Summary	87
7.2 Port Config	88
7.3 MSTP Instance	90
7.3.1 Region Config	90
7.3.2 Instance Config	91
7.3.3 Instance Port Config	92
7.4 STP Security	93
7.4.1 Port Protect	93
7.5 Application Example for STP Function	96
Chapter 8 Multicast	101
8.1 IGMP Snooping	103
8.1.1 Snooping Config	105
8.1.2 Port Config	107
8.1.3 VLAN Config	108
8.1.4 Multicast VLAN	109
8.1.5 Querier Config	113
8.1.6 Profile Config	114
8.1.7 Profile Binding	116
8.1.8 Packet Statistics	117
8.2 Multicast Table	118
8.2.1 IPv4 Multicast Table	119
8.2.2 Static IPv4 Multicast Table	119
Chapter 9 QoS	122
9.1 DiffServ	125
9.1.1 Port Priority	125
9.1.2 Schedule Mode	126
9.1.3 802.1P Priority	127
9.1.4 DSCP Priority	128
9.2 Bandwidth Control	129
9.2.1 Rate Limit	129
9.2.2 Storm Control	130
9.3 Voice VLAN	131
9.3.1 Global Config	134
9.3.2 Port Config	134
9.3.3 OUI Config	136
Chapter 10 PoE	138
10.1 PoE Config	139
10.1.1 PoE Config	139
10.1.2 PoE Profile	140
10.2 Time-Range	141
10.2.1 Time-Range Summary	141
10.2.2 Time-Range Create	142
10.2.3 Holiday Config	144
Chapter 11 ACL	145
11.1 ACL Config	145
11.1.1 ACL Summary	145
11.1.2 ACL Create	145
11.1.3 MAC ACL	146
11.1.4 Standard-IP ACL	147
11.1.5 Extend-IP ACL	147
11.2 Policy Config	148
11.2.1 Policy Summary	149
11.2.2 Policy Create	149
11.2.3 Action Create	149
11.3 ACL Binding	150
11.3.1 Binding Table	150
11.3.2 Port Binding	151
11.3.3 VLAN Binding	152
11.4 Policy Binding	153
11.4.1 Binding Table	153
11.4.2 Port Binding	154
11.4.3 VLAN Binding	155
11.5 Application Example for ACL	156
Chapter 12 Network Security	158
12.1 IP-MAC Binding	158
12.1.1 Binding Table	158
12.1.2 Manual Binding	160
12.1.3 ARP Scanning	161
12.2 DHCP Snooping	163
12.2.1 Global Config	166
12.2.2 Port Config	167
12.2.3 Option 82 Config	168
12.3 ARP Inspection	169
12.3.1 ARP Detect	172
12.3.2 ARP Defend	174
12.3.3 ARP Statistics	175
12.4 DoS Defend	175
12.4.1 DoS Defend	177
12.5 802.1X	178
12.5.1 Global Config	182
12.5.2 Port Config	184
12.6 AAA	186
12.6.1 Global Config	187
12.6.2 Privilege Elevation	187
12.6.3 RADIUS Server Config	187
12.6.4 TACACS+ Server Config	188
12.6.5 Authentication Server Group Config	189
12.6.6 Authentication Method List Config	191
12.6.7 Application Authentication List Config	192
12.6.8 802.1X Authentication Server Config	193
12.6.9 Default Settings	193
Chapter 13 SNMP	195
13.1 SNMP Config	197
13.1.1 Global Config	197
13.1.2 SNMP View	198
13.1.3 SNMP Group	199
13.1.4 SNMP User	201
13.1.5 SNMP Community	202
13.2 Notification	205
13.3 RMON	206
13.3.1 Statistics	207
13.3.2 History	208
13.3.3 Event	209
13.3.4 Alarm	210
Chapter 14 LLDP	212
14.1 Basic Config	217
14.1.1 Global Config	217
14.1.2 Port Config	218
14.2 Device Info	219
14.2.1 Local Info	219
14.2.2 Neighbor Info	221
14.3 Device Statistics	222
14.4 LLDP-MED	223
14.4.1 Global Config	224
14.4.2 Port Config	225
14.4.3 Local Info	226
14.4.4 Neighbor Info	227
Chapter 15 Maintenance	229
15.1 System Monitor	229
15.1.1 CPU Monitor	229
15.1.2 Memory Monitor	230
15.2 Log	231
15.2.1 Log Table	232
15.2.2 Local Log	233
15.2.3 Remote Log	233
15.2.4 Backup Log	234
15.3 Device Diagnostics	235
15.3.1 Cable Test	235
15.4 Network Diagnostics	236
15.4.1 Ping	236
15.4.2 Tracert	237
Appendix A: Specifications	238

Match case Limit results 1 per page



Loop Protect

In a stable network, a switch maintains the states of ports by receiving and processing BPDU

packets from the upstream switch. However, when link congestions or link failures occurred to

the network, a down stream switch does not receive BPDU packets for certain period, which

results in spanning trees being regenerated and roles of ports being reselected, and causes

the blocked ports to transit to forwarding state. Therefore, loops may be incurred in the

network.

The loop protect function can suppresses loops. With this function enabled, a port, regardless

of the role it plays in instances, is always set to blocking state, when the port does not receive

BPDU packets from the upstream switch and spanning trees are regenerated, and thereby

loops can be prevented.



Root Protect

A CIST and its secondary root bridges are usually located in the high-bandwidth core region.

Wrong configuration or malicious attacks may result in configuration BPDU packets with higher

priorities being received by the legal root bridge, which causes the current legal root bridge to

lose its position and network topology jitter to occur. In this case, flows that should travel along

high-speed links may lead to low-speed links, and network congestion may occur.

To avoid this, MSTP provides root protect function. Ports with this function enabled can only be

set as designated ports in all spanning tree instances. When a port of this type receives BDPU

packets with higher priority, it transits its state to blocking state and stops forwarding packets

(as if it is disconnected from the link). The port resumes the normal state if it does not receive

any configuration BPDU packets with higher priorities for a period of two times of forward

delay.



TC Protect

A switch removes MAC address entries upon receiving TC-BPDU packets. If a user maliciously

sends a large amount of TC-BPDU packets to a switch in a short period, the switch will be busy

with removing MAC address entries, which may decrease the performance and stability of the

network.

To prevent the switch from frequently removing MAC address entries, you can enable the TC

protect function on the switch. With TC protect function enabled, if the account number of the

received TC-BPDUs exceeds the maximum number you set in the TC threshold field, the switch

will not performs the removing operation in the TC protect cycle. Such a mechanism prevents

the switch from frequently removing MAC address entries.



BPDU Protect

Ports of the switch directly connected to PCs or servers are configured as edge ports to

rapidly transit their states. When these ports receive BPDUs, the system automatically

configures these ports as non-edge ports and regenerates spanning trees, which may cause

network topology jitter. Normally these ports do not receive BPDUs, but if a user maliciously

attacks the switch by sending BPDUs, network topology jitter occurs.

To prevent this attack, MSTP provides BPDU protect function. With this function enabled on the

switch, the switch shuts down the edge ports that receive BPDUs and reports these cases to

the administrator. If a port is shut down, only the administrator can restore it.