606
C
HAPTER
57: DHCP S
ERVER
C
ONFIGURATION
DHCP Security
Configuration
DHCP security configuration is needed to ensure the security of DHCP service.
Prerequisites
Before configuring DHCP security, you should first complete the DHCP server
configuration (either global address pool-based or interface address pool-based
DHCP server configuration).
Configuring Private
DHCP Server Detecting
A private DHCP server on a network also answers IP address request packets and
assigns IP addresses to DHCP clients. However, the IP addresses they assigned may
conflict with those of other hosts. As a result, users cannot normally access
networks. This kind of DHCP servers are known as private DHCP servers.
With the private DHCP server detecting function enabled, when a DHCP client
sends the DHCP-REQUEST packet, the DHCP server tracks the information (such as
the IP addresses and interfaces) of DHCP servers to enable the administrator to
detect private DHCP servers in time and take proper measures.
Configuring IP Address
Detecting
To avoid IP address conflicts caused by assigning the same IP address to multiple
DHCP clients simultaneously, you can configure a DHCP server to detect an IP
address before it assigns the address to a DHCP client.
IP address detecting is achieved by performing ping operations. To detect whether
an IP address is currently in use, the DHCP server sends an ICMP packet with the IP
address to be assigned as the destination and waits for a response. If the DHCP
server receives no response within a specified time, it resends an ICMP packet. This
procedure repeats until the DHCP server receives a response or the number of the
sent ICMP packets reaches the specified maximum number. The DHCP server
assigns the IP address to the DHCP client only when no response is received during
the whole course, thus ensuring that an IP address is assigned to one DHCP client
exclusively.
Table 478
Enable detection of a private DHCP server
Operation Command Description
Enter system view
system-view
-
Enable the private DHCP
server detecting function
dhcp server detect
Required
By default, the private DHCP
server detecting function is
disabled
Table 479
Configure IP address detecting
Operation Command
Description
Enter system view
system-view
-
Set the maximum number of
ICMP packets a DHCP server
sends in a ping test
dhcp server ping packets
number
Optional
By default, a DHCP server
performs the ping operation
twice to test an IP address
Set the response timeout time
of each ICMP packet
dhcp server ping timeout
milliseconds
Optional
The default timeout time is 500
milliseconds
Summary of Contents for Switch 7754
Page 32: ...32 CHAPTER 1 CLI OVERVIEW ...
Page 70: ...70 CHAPTER 5 LOGGING IN USING MODEM ...
Page 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS ...
Page 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT ...
Page 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION ...
Page 126: ...126 CHAPTER 14 SUPER VLAN ...
Page 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION ...
Page 152: ...152 CHAPTER 17 IPX CONFIGURATION ...
Page 164: ...164 CHAPTER 19 QINQ CONFIGURATION ...
Page 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION ...
Page 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION ...
Page 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION ...
Page 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION ...
Page 224: ...224 CHAPTER 27 DLDP CONFIGURATION ...
Page 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT ...
Page 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION ...
Page 280: ...280 CHAPTER 30 MSTP CONFIGURATION ...
Page 348: ...348 CHAPTER 35 IS IS CONFIGURATION ...
Page 408: ...408 CHAPTER 39 802 1X CONFIGURATION ...
Page 412: ...412 CHAPTER 40 HABP CONFIGURATION ...
Page 422: ...422 CHAPTER 41 MULTICAST OVERVIEW ...
Page 426: ...426 CHAPTER 42 GMRP CONFIGURATION ...
Page 480: ...480 CHAPTER 47 PIM CONFIGURATION ...
Page 506: ...506 CHAPTER 48 MSDP CONFIGURATION ...
Page 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION ...
Page 570: ...570 CHAPTER 53 HA CONFIGURATION ...
Page 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200 ...
Page 622: ...622 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Page 684: ...684 CHAPTER 61 QOS CONFIGURATION ...
Page 718: ...718 CHAPTER 63 CLUSTER ...
Page 738: ...738 CHAPTER 67 UDP HELPER CONFIGURATION ...
Page 752: ...752 CHAPTER 69 RMON CONFIGURATION ...
Page 772: ...772 CHAPTER 70 NTP CONFIGURATION ...
Page 796: ...796 CHAPTER 72 FILE SYSTEM MANAGEMENT ...
Page 802: ...802 CHAPTER 73 BIMS CONFIGURATION ...
Page 814: ...814 CHAPTER 74 FTP AND TFTP CONFIGURATION ...
Page 830: ...830 CHAPTER 75 INFORMATION CENTER ...
Page 836: ...836 CHAPTER 76 DNS CONFIGURATION ...
Page 852: ...852 CHAPTER 77 BOOTROM AND HOST SOFTWARE LOADING ...
Page 858: ...858 CHAPTER 78 BASIC SYSTEM CONFIGURATION DEBUGGING ...