336
C
HAPTER
21: C
ONFIGURING
IP A
PPLICATION
will take back the IP address. If the DHCP client wants to continue to use
this address, it should renew the IP leasing contract such as extending the
leasing contract of the IP address.
■
In practice, the DHCP client will automatically send the message for
renewing the IP leasing contract to the DHCP server when the DHCP client
starts up or half of the valid period of the IP leasing contract has expired. To
renew the IP leasing contract, the DHCP client will send a DHCP_Discover
message to the DHCP server. If the IP address is valid, the DHCP server will
send back a DHCP_ACK message to notify the DHCP client that it has
obtained a new IP leasing contract. In addition, the
ipconfig /renew
command can be used on the user PC (that is, the DHCP client) to renew its
IP leasing contract.
■
Priority sequence in which the DHCP server allocates IP address to the client
The DHCP server will select an IP address for a client in the following order:
a
IP address in the DHCP Server database, which is statically bound with the
MAC address of the client.
b
IP address that was used by the client.
c
Address in the requested IP address option contained in the DHCP_Discover
message sent by the client.
d
IP address that is first found when searching for the IP addresses available for
allocation in the DHCP address pool in sequence.
e
Report the error, if no IP address is available for allocation after going through
the above steps.
■
Applications of DHCP Server
In practice, to improve the serving efficiency of DHCP servers, a DHCP server
will probably be used to serve the clients beyond the LAN. Normally, routers
have been added with the function of DHCP relay proxy (that is, providing the
across-segment transmission of DHCP packets). Clients in the LAN can
communicate with the DHCP servers in other subnetworks through the DHCP
relay proxy and finally obtain legal IP addresses.
Figure 125
Integrated networking application of DHCP server and DHCP relay
Normally, DHCP relay proxy can either be a host or a router as long as the
service program of DHCP relay proxy is enabled.
DHCP Server
Configuration
DHCP server configuration includes:
■
Enable/Disable the DHCP service
■
Create a DHCP address pool
LAN
Router
DHCP Server
Client
Client
Client
Client
Internet
Router
DHCP Relay
Содержание 3036
Страница 1: ...http www 3com com 3Com Router Configuration Guide Published March 2004 Part No 10014299 ...
Страница 4: ...VPN 615 RELIABILITY 665 QOS 681 DIAL UP 721 ...
Страница 6: ...2 ABOUT THIS GUIDE ...
Страница 7: ...I GETTING STARTED Chapter 1 3Com Router Introduction Chapter 2 3Com Router User Interface ...
Страница 8: ...4 ...
Страница 16: ...12 CHAPTER 1 3COM ROUTER INTRODUCTION ...
Страница 34: ...30 ...
Страница 60: ...56 CHAPTER 3 SYSTEM MANAGEMENT ...
Страница 88: ...84 CHAPTER 5 CONFIGURING NETWORK MANAGEMENT RouterA interface ethernet 0 RouterA Ethernet0 rmon promiscuous ...
Страница 98: ...94 CHAPTER 6 DISPLAY AND DEBUGGING TOOLS ...
Страница 110: ...106 ...
Страница 114: ...110 CHAPTER 8 INTERFACE CONFIGURATION OVERVIEW ...
Страница 158: ...154 CHAPTER 10 CONFIGURING WAN INTERFACE ...
Страница 168: ...164 ...
Страница 188: ...184 CHAPTER 13 CONFIGURING PPPOE CLIENT ...
Страница 192: ...188 CHAPTER 14 CONFIGURING SLIP Router ip route static 0 0 0 0 0 0 0 0 10 110 0 1 ...
Страница 248: ...244 CHAPTER 16 CONFIGURING LAPB AND X 25 ...
Страница 292: ...288 CHAPTER 18 CONFIGURING HDLC Enable HDLC packet debugging debugging hdlc packet interface type number ...
Страница 320: ...316 ...
Страница 330: ...326 CHAPTER 20 CONFIGURING IP ADDRESS ...
Страница 362: ...358 CHAPTER 21 CONFIGURING IP APPLICATION ...
Страница 374: ...370 CHAPTER 23 CONFIGURING IP COUNT ...
Страница 406: ...402 CHAPTER 25 CONFIGURING DLSW ...
Страница 408: ...404 ...
Страница 452: ...448 CHAPTER 29 CONFIGURING OSPF ...
Страница 482: ...478 CHAPTER 30 CONFIGURING BGP ...
Страница 494: ...490 CHAPTER 31 CONFIGURING IP ROUTING POLICY ...
Страница 502: ...498 ...
Страница 508: ...504 CHAPTER 33 IP MULTICAST ...
Страница 514: ...510 CHAPTER 34 CONFIGURING IGMP ...
Страница 526: ...522 CHAPTER 36 CONFIGURING PIM SM ...
Страница 528: ...524 ...
Страница 532: ...528 CHAPTER 37 CONFIGURING TERMINAL ACCESS SECURITY ...
Страница 550: ...546 CHAPTER 38 CONFIGURING AAA AND RADIUS PROTOCOL ...
Страница 590: ...586 CHAPTER 40 CONFIGURING IPSEC ...
Страница 599: ...IX VPN Chapter 42 Configuring VPN Chapter 43 Configuring L2TP Chapter 44 Configuring GRE ...
Страница 600: ...596 ...
Страница 638: ...634 CHAPTER 43 CONFIGURING L2TP ...
Страница 649: ...X RELIABILITY Chapter 45 Configuring a Standby Center Chapter 46 Configuring VRRP ...
Страница 650: ...646 ...
Страница 666: ...662 ...
Страница 670: ...666 CHAPTER 47 QOS OVERVIEW ...
Страница 700: ...696 CHAPTER 49 CONGESTION MANAGEMENT ...
Страница 706: ...702 CHAPTER 50 CONGESTION AVOIDANCE ...
Страница 707: ...XII DIAL UP Chapter 51 Configuring DCC Chapter 52 Configuring Modem ...
Страница 708: ...704 ...
Страница 762: ...758 CHAPTER 52 CONFIGURING MODEM ...