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ZyXEL GS1500-24P User Guide - Page 132

ARP Table Entries, How Dynamic ARP Works, ARP Inspection Overview

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Chapter 18 Dynamic ARP 18.3.1 ARP Table Entries The ARP table is populated with MAC and corresponding IP address mappings in two different ways. • DHCP Snooping - The Switch listens to traffic from a DHCP server on a trusted port and learns IP-to-MAC address bindings by parsing DHCP ACK packets. • Static Entries - The Switch administrator can enter static IP-to-MAC address mappings via the web configurator. 18.3.2 How Dynamic ARP Works When an incoming ARP packet destined for a host device on a local area network arrives at the Switch, the Switch's ARP program looks in the ARP table and, if it finds the address, sends it to the device. If no entry is found for the IP address, dynamic ARP discards the ARP packet. 18.3.3 ARP Inspection Overview Use ARP inspection to filter unauthorized ARP packets on the network. This can prevent many kinds of man-in-the-middle attacks, such as the one in the following example. Figure 63 Example: Man-in-the-middle Attack 132 In this example, computer B tries to establish a connection with computer A. Computer X is in the same broadcast domain as computer A and intercepts the ARP request for computer A. Then, computer X does the following things: • It pretends to be computer A and responds to computer B. • It pretends to be computer B and sends a message to computer A. As a result, all the communication between computer A and computer B passes through computer X. Computer X can read and alter the information passed between them. GS1500-24P User's Guide

Section	Page
GS1500-24P	1
About This User's Guide	3
Document Conventions	5
Safety Warnings	7
Contents Overview	9
Table of Contents	11
Introduction and Hardware	19
Getting to Know Your Switch	21
1.1 Introduction	21
1.1.1 Backbone Application	21
1.1.2 Bridging Example	22
1.1.3 High Performance Switching Example	23
1.1.4 IEEE 802.1Q VLAN Application Examples	23
1.2 Ways to Manage the Switch	24
1.3 Good Habits for Managing the Switch	24
Hardware Installation and Connection	27
2.1 Installation Scenarios	27
2.2 Desktop Installation Procedure	27
2.3 Mounting the Switch on a Rack	27
2.3.1 Rack-mounted Installation Requirements	28
2.3.2 Attaching the Mounting Brackets to the Switch	28
2.3.3 Mounting the Switch on a Rack	29
Hardware Panels	31
3.1 Overview	31
3.2 Front Panel	31
3.2.1 Gigabit Ethernet Ports	32
3.2.2 Mini-GBIC Slots	33
3.2.3 The RESET Button	35
3.3 Rear Panel	35
3.3.1 Power Connector	35
3.4 LEDs	35
Basic Configuration	37
The Web Configurator	39
4.1 Overview	39
4.2 System Login	39
4.3 The Status Screen	40
4.3.1 Change Your Password	44
4.4 Saving Your Configuration	44
4.5 Switch Lockout	44
4.6 Resetting the Switch	45
4.7 Logging Out of the Web Configurator	45
Initial Setup Example	47
5.1 Overview	47
5.1.1 Creating a VLAN	47
5.1.2 Setting Port VID	48
5.2 Configuring Switch Management IP Address	49
System	51
6.1 Overview	51
6.2 What You Can Do	51
6.3 Information	52
6.4 Time Setting	53
6.5 IP Setting Screen	53
6.6 User Account	54
6.7 Port Setting	55
Configuration	57
Link Aggregation	59
7.1 Overview	59
7.2 What You Can Do	59
7.3 What You Need to Know	59
7.3.1 Dynamic Link Aggregation	60
7.4 Trunk Group Setting	60
7.5 Trunk Distribution Algorithm	62
7.6 LACP Setting	63
7.7 Technical Reference	64
7.7.1 Static Trunking Example	64
VLAN	67
8.1 Overview	67
8.2 What You Can Do	67
8.3 What You Need to Know	67
8.3.1 IEEE 802.1Q Tagged VLANs	67
8.3.2 Forwarding Tagged and Untagged Frames	68
8.3.3 Common IEEE 802.1Q VLAN terminology	68
8.3.4 Static VLAN	69
8.4 Static VLAN	69
8.5 Port-based VLAN	71
Spanning Tree Protocol	73
9.1 Overview	73
9.2 What You Can Do	73
9.3 What You Need to Know	73
9.3.1 STP Terminology	74
9.3.2 How STP Works	74
9.3.3 STP Port States	74
9.4 STP Global Setting	75
9.5 STP Port Setting	77
QoS	79
10.1 Overview	79
10.2 What You Can Do	79
10.3 What You Need to Know	80
10.3.1 DiffServ	80
10.3.2 DSCP and Per-Hop Behavior	80
10.3.3 DiffServ Network Example	81
10.4 Port-based Priority	81
10.5 DSCP-to-IEEE 802.1p Priority Settings	82
10.5.1 DSCP-based Priority	83
10.6 Policy-based Priority	83
10.6.1 Policy-based Priority - Add/Modify	85
10.7 Priority to Queue Mapping	86
10.8 Packet Scheduling	87
10.8.1 Strictly Priority Queuing	87
10.8.2 Weighted Fair Queuing	87
10.8.3 Weighted Round Robin Scheduling (WRR)	88
Mirroring	91
11.1 Overview	91
11.2 What You Can Do	91
11.3 Port-based Mirroring	92
11.4 Policy-based Mirroring	93
11.4.1 Policy-based Mirroring - Add/Modify	93
SNMP	95
12.1 Overview	95
12.2 What You Can Do	95
12.3 What You Need to Know	95
12.3.1 About SNMP	95
12.4 SNMP Setting	97
12.5 SNMPv3 Setting	99
12.6 Technical Reference	103
Rate Limit	107
13.1 Rate Limit Overview	107
13.2 What You Can Do	107
13.3 Rate Limit Summary	107
13.3.1 Rate Limit Add/Modify	108
Bandwidth Control and Jumbo Frame	111
14.1 Bandwidth Control and Jumbo Frame Overview	111
14.2 What You Can Do	111
14.3 Bandwidth Control	112
14.4 Jumbo Frame Setting	113
Power Over Ethernet	115
15.1 Power Over Ethernet Overview	115
15.2 What You Can Do	115
15.3 Power Over Ethernet	116
Security	119
MAC Address	121
16.1 Overview	121
16.2 What You Can Do	121
16.2.1 MAC Forwarding Table	122
16.2.2 Static MAC Address Forwarding	122
16.3 MAC Forwarding Table	123
16.4 Static MAC	123
16.5 MAC Filtering	124
802.1x	127
17.1 Overview	127
17.2 What You Can Do	127
17.3 What You Need to Know	128
17.3.1 IEEE 802.1x Authentication	128
17.4 Port Authentication Configuration	128
17.5 802.1x Setting	129
17.6 802.1x Port Setting	130
Dynamic ARP	131
18.1 ARP Table Overview	131
18.2 What You Can Do	131
18.3 What You Need to Know	131
18.3.1 ARP Table Entries	132
18.3.2 How Dynamic ARP Works	132
18.3.3 ARP Inspection Overview	132
18.3.4 MAC-IP Binding	133
18.4 Dynamic ARP Setting	133
18.5 Dynamic ARP VLAN Setting	134
18.6 MAC-IP Binding Config	135
Storm Control	137
19.1 Overview	137
19.2 What You Can Do	137
19.3 Storm Control Setting	138
Defence Engine	139
20.1 Overview	139
20.2 What You Can Do	139
20.3 Activating Defence Engine	139
Monitoring and Tools	141
Monitoring	143
21.1 Overview	143
21.2 What You Can Do	143
21.3 Logging Setting	143
21.4 Logging Viewing	145
21.5 Port Statistics	147
Tools	149
22.1 Overview	149
22.2 What You Can Do	149
22.3 TFTP	149
22.4 Reset	151
22.5 Reboot	151
Troubleshooting & Product Specifications	155
Troubleshooting	157
23.1 Power, Hardware Connections, and LEDs	157
23.2 Switch Access and Login	158
Product Specifications	161
Appendices and Index	167
Changing a Fuse	169
Common Services	171
Legal Information	175
Open Software Announcements	179