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The Format of DHCP Message

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when its lease time expires. If the client wants to use the IP address continually, it should unicast a DHCP-REQUEST message to the server to extend its lease. After obtaining parameters via DHCP, a host should be able to exchange packets with any other host in the networks.  The Format of DHCP Message Figure 8-1 DHCP model gives the process of DHCP and Figure 8-3 describes each field in the DHCP message. The numbers in parentheses indicate the size of each field in octets. The names for the fields given in the figure will be used throughout this document to refer to the fields in DHCP messages. Figure 8-3 The Format of DHCP Message 1) op：Message type, '1' = BOOT-REQUEST, '2' = BOOT-REPLY. 2) htype：Hardware address type, '1' for ethernet. 3) hlen：Hardware address length, '6' for ethernet. 4) hops：Clients set this field to zero and broadcast the DHCP-REQUEST message, optionally used by relay-agents when booting via a relay-agent. 5) xid：Transaction ID, a random number chosen by the client, used by the client and server to associate messages. 6) secs：Filled in by client, seconds elapsed since client started trying to boot. 7) flags：A client that cannot receive unicast IP datagrams until its protocol software has been configured with an IP address should set the first bit in the 'flags' field to 1 in any DHCP-DISCOVER or DHCP-REQUEST message that client sends. A client that can receive unicast IP datagrams before its protocol software has been configured should clear the first bit to 0. A server or relay agent sending or relaying a DHCP message directly to a DHCP client should examine the first bit in the 'flags' field. If this bit is set to 1, the DHCP message should be sent as an IP broadcast and if the bit is cleared to 0, the message should be sent as an IP unicast. The remaining bits of the flags field are reserved for future use and must be set to zero by clients and ignored by servers and relay agents. 114

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	13
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	18
Chapter 3 Login to the Switch	19
3.1 Login	19
3.2 Configuration	19
Chapter 4 System	21
4.1 System Info	21
4.1.1 System Summary	21
4.1.2 Device Description	23
4.1.3 System Time	23
4.1.4 Daylight Saving Time	24
4.1.5 System IP	26
4.1.6 System IPv6	27
4.2 User Management	35
4.2.1 User Table	35
4.2.2 User Config	36
4.3 System Tools	37
4.3.1 Boot Config	37
4.3.2 Config Restore	38
4.3.3 Config Backup	38
4.3.4 Firmware Upgrade	39
4.3.5 System Reboot	39
4.3.6 System Reset	40
4.4 Access Security	40
4.4.1 Access Control	40
4.4.2 HTTP Config	41
4.4.3 HTTPS Config	42
4.4.4 SSH Config	46
4.4.5 Telnet Config	52
Chapter 5 Switching	53
5.1 Port	53
5.1.1 Port Config	53
5.1.2 Port Mirror	54
5.1.3 Port Security	56
5.1.4 Port Isolation	58
5.1.5 Loopback detection	59
5.2 LAG	60
5.2.1 LAG Table	61
5.2.2 Static LAG	62
5.2.3 LACP Config	63
5.3 Traffic Monitor	65
5.3.1 Traffic Summary	65
5.3.2 Traffic Statistics	66
5.4 MAC Address	67
5.4.1 Address Table	68
5.4.2 Static Address	69
5.4.3 Dynamic Address	71
5.4.4 Filtering Address	73
5.5 L2PT	74
5.5.1 L2PT Config	75
Chapter 6 VLAN	77
6.1 802.1Q VLAN	78
6.1.1 VLAN Config	80
6.1.2 Port Config	82
6.2 MAC VLAN	84
6.2.1 MAC VLAN	84
6.3 Protocol VLAN	86
6.3.1 Protocol Group Table	86
6.3.2 Protocol Group	87
6.3.3 Protocol Template	88
6.4 Application Example for 802.1Q VLAN	89
6.5 Application Example for MAC VLAN	90
6.6 Application Example for Protocol VLAN	92
6.7 VLAN VPN	94
6.7.1 VPN Config	95
6.7.2 VLAN Mapping	96
6.8 GVRP	97
Chapter 7 Spanning Tree	101
7.1 STP Config	106
7.1.1 STP Config	106
7.1.2 STP Summary	108
7.2 Port Config	108
7.3 MSTP Instance	110
7.3.1 Region Config	111
7.3.2 Instance Config	111
7.3.3 Instance Port Config	113
7.4 STP Security	114
7.4.1 Port Protect	115
7.4.2 TC Protect	117
7.5 Application Example for STP Function	117
Chapter 8 DHCP	122
8.1 DHCP Relay	126
Chapter 9 Multicast	131
9.1 IGMP Snooping	135
9.1.1 Snooping Config	137
9.1.2 VLAN Config	138
9.1.3 Port Config	139
9.1.4 IP-Range	141
9.1.5 Multicast VLAN	142
9.1.6 Static Multicast IP	145
9.1.7 IGMP Snooping Querier	146
9.1.8 Packet Statistics	148
9.1.9 IGMP Authentication	150
9.2 MLD Snooping	151
9.2.1 Global Config	153
9.2.2 VLAN Config	154
9.2.3 Filter Config	155
9.2.4 Port Config	156
9.2.5 Static Multicast	157
9.2.6 Querier Config	158
9.2.7 Packet Statistics	159
9.3 Multicast Table	161
9.3.1 IPv4 Multicast Table	161
9.3.2 IPv6 Multicast Table	162
Chapter 10 QoS	163
10.1 DiffServ	166
10.1.1 Port Priority	166
10.1.2 DSCP Priority	167
10.1.3 802.1P/CoS Mapping	169
10.1.4 Schedule Mode	170
10.2 Bandwidth Control	171
10.2.1 Rate Limit	171
10.2.2 Storm Control	172
10.3 Voice VLAN	174
10.3.1 Global Config	176
10.3.2 Port Config	177
10.3.3 OUI Config	178
Chapter 11 ACL	180
11.1 Time-Range	180
11.1.1 Time-Range Summary	180
11.1.2 Time-Range Create	181
11.1.3 Holiday Config	182
11.2 ACL Config	183
11.2.1 ACL Summary	183
11.2.2 ACL Create	183
11.2.3 MAC ACL	184
11.2.4 Standard-IP ACL	185
11.2.5 Extend-IP ACL	186
11.3 Policy Config	187
11.3.1 Policy Summary	187
11.3.2 Policy Create	188
11.3.3 Action Create	189
11.4 Policy Binding	190
11.4.1 Binding Table	190
11.4.2 Port Binding	191
11.4.3 VLAN Binding	191
11.5 Application Example for ACL	192
Chapter 12 Network Security	195
12.1 IP-MAC Binding	195
12.1.1 Binding Table	195
12.1.2 Manual Binding	197
12.1.3 ARP Scanning	198
12.1.4 DHCP Snooping	200
12.2 ARP Inspection	205
12.2.1 ARP Detect	209
12.2.2 ARP Defend	210
12.2.3 ARP Statistics	211
12.3 DoS Defend	212
12.3.1 DoS Defend	213
12.4 802.1X	214
12.4.1 Global Config	218
12.4.2 Port Config	220
12.5 AAA	222
12.5.1 Global Config	223
12.5.2 Privilege Elevation	223
12.5.3 RADIUS Server Config	224
12.5.4 TACACS+ Server Config	225
12.5.5 Authentication Server Group Config	225
12.5.6 Authentication Method List Config	227
12.5.7 Application Authentication List Config	228
12.5.8 802.1X Authentication Server Config	229
12.5.9 Default Settings	230
12.6 PPPoE	231
Chapter 13 SNMP	234
13.1 SNMP Config	236
13.1.1 Global Config	236
13.1.2 SNMP View	237
13.1.3 SNMP Group	238
13.1.4 SNMP User	240
13.1.5 SNMP Community	241
13.2 Notification	244
13.2.1 Notification Config	244
13.3 RMON	246
13.3.1 History Control	247
13.3.2 Event Config	248
13.3.3 Alarm Config	249
Chapter 14 LLDP	251
14.1 Basic Config	255
14.1.1 Global Config	255
14.1.2 Port Config	256
14.2 Device Info	257
14.2.1 Local Info	257
14.2.2 Neighbor Info	258
14.3 Device Statistics	259
14.4 LLDP-MED	260
14.4.1 Global Config	261
14.4.2 Port Config	262
14.4.3 Local Info	264
14.4.4 Neighbor Info	265
Chapter 15 Maintenance	267
15.1 System Monitor	267
15.1.1 CPU Monitor	267
15.1.2 Memory Monitor	268
15.2 Log	269
15.2.1 Log Table	270
15.2.2 Local Log	271
15.2.3 Remote Log	272
15.2.4 Backup Log	272
15.3 Device Diagnostics	273
15.4 Network Diagnostics	274
15.4.1 Ping	274
15.4.2 Tracert	275
15.5 DLDP	276
Chapter 16 System Maintenance via FTP	280

Match case Limit results 1 per page

114

when its lease time expires. If the client wants to use the IP address continually, it should

unicast a DHCP-REQUEST message to the server to extend its lease.

After obtaining parameters via DHCP, a host should be able to exchange packets with any

other host in the networks.



The Format of DHCP Message

Figure 8-1

DHCP model gives the process of DHCP and Figure 8-3 describes each field in the

DHCP message. The numbers in parentheses indicate the size of each field in octets. The

names for the fields given in the figure will be used throughout this document to refer to the

fields in DHCP messages.

Figure 8-3 The Format of DHCP Message

：

Message type, ‘1’ = BOOT-REQUEST, ‘2’ = BOOT-REPLY.

htype

：

Hardware address type, '1' for ethernet.

hlen

：

Hardware address length, '6' for ethernet.

hops

：

Clients set this field to zero and broadcast the DHCP-REQUEST message, optionally

used by relay-agents when booting via a relay-agent.

xid

：

Transaction ID, a random number chosen by the client, used by the client and server to

associate messages.

secs

：

Filled in by client, seconds elapsed since client started trying to boot.

flags

：

A client that cannot receive unicast IP datagrams until its protocol software has been

configured with an IP address should set the first bit in the 'flags' field to 1 in any

DHCP-DISCOVER or DHCP-REQUEST message that client sends. A client that can receive

unicast IP datagrams before its protocol software has been configured should clear the

first bit to 0. A server or relay agent sending or relaying a DHCP message directly to a

DHCP client should examine the first bit in the 'flags' field. If this bit is set to 1, the DHCP

message should be sent as an IP broadcast and if the bit is cleared to 0, the message

should be sent as an IP unicast. The remaining bits of the flags field are reserved for future

use and must be set to zero by clients and ignored by servers and relay agents.