In networking infrastructure, DHCP server is very essential services to provide IP configuration automatically to hosts including the computers on the network. With the proper IP configuration to the hosts on the network, all the hosts can communicate each other.
Deploying the IP address manually to hundreds of computers on the network is prone to the IP addresses conflict due to miss-typing - a normal human error. DHCP server is designed to help the network administrator to reduce the complexity of administrating the IP address configurations. By issues leases from a central database, DHCP server automatically manages address assignment and configure other essential settings for your network clients.
Deploying the IP address manually to hundreds of computers on the network is prone to the IP addresses conflict due to miss-typing - a normal human error. DHCP server is designed to help the network administrator to reduce the complexity of administrating the IP address configurations. By issues leases from a central database, DHCP server automatically manages address assignment and configure other essential settings for your network clients.
In windows networking, when the DHCP server is not available, the clients will adopt the alternate configuration or APIPA (Automatic Private IP Addressing) The range of APIPA addressing is between 169.254.0.0 until 169.254.255.254. If the computer in the network (with DHCP server available) receives the IP address in the APIPA range, it indicates that the computer is not connected or there is connectivity problem. See also wireless network troubleshooting.
Network administrator should configure the IP address or the pool of the IP address that will assigned to the computers in the network. In Windows system, the clients lease addresses for a specific length of time from the DHCP server. Once 50% of the lease has expired, the clients will attempt to renew the same IP address. The DHCP server will renew addresses for another lease period.
DHCP server Scopes
A DHCP scope is a pool of IP addresses within a logical subnet, for example 192.168.1.1 through 192.168.1.220 that the DHCP server to manage distribution and assignment of IP addresses and of any releated configuration parameters (such as DNS, gateway) to clients on the network. Once DHCP scope is for one DHCP server can serve multiple subnets.
DHCP server scope specifies the range of addresses available for lease. An IP address within a defined scope that is offered to a DHCP client is known as a lease. Each lease has a specified duration, and the clients must periodically renew the lease.
An exclusion range can be set within the range of defined scope if you don't want to lease to DHCP clients. Exclusion range assures that the DHCP server does not offer the exclusion range to DHCP clients. You can also provide reserve addresses for specific clients with MAC addresses which are typically used for servers, printers and other network devices that require static IP addresses.
How the process of DHCP server to the clients?
To configure a client to receive its IP address information from a DHCP server, the TCP/IP configuration of the computers must be configured to "obtain an IP address automatically" options. To configure the client to receive DNS options from the DHCP server, you should select the "obtain DNS server Address Automatically" option.
DHCP servers use private IP address instead of IP addresses ( registered IP address), since private IP addresses are not rout ableto the Internet, thus with the dual firewall features of the firewall will help you reduce network security threats from the Internet.
How to Configure DHCP server in Wireless Routers
Mostly all the wireless routers including the routers with build-in DSL modem or routers with build-in cable modem are powered by the DHCP server which enabled by default. So anyone that knows nothing about DHCP server, no worries - just leave the default setting.
Open the router configuration menu from the web-based utility by typing the default IP address of the wireless routers for example http://192.168.1.1 (For linksys) and press enter. The login dialog prompts you to type in the user-name and password of the router. The following table shows some wireless routers with their default IP address, user-name and password.
Find the configuration menu with relates to DHCP menu or similar one (refer to manual book of the router). DHCP Server is enabled by factory default.If you already have a DHCP server on your network, or you don't want a DHCP server, then select disabled.
Starting IP address: Enter a value for the DHCP server to start with when issuing IP addresses. Assume the Router's default IP address is 192.168.1.1, the starting IP Address must be 192.168.1.2 or greater, but smaller than 192.168.1.253.
Maximum number of DHCP Users: Enter the Maximum number of PCs that you want the DHCP server to assign IP addresses to. This number cannot be greater than 253. The default is 50.
Client Lease Time: The Client Lease Time is the amount of time a network users will be allowed connection to the router with their current dynamic IP address. Enter the amount of time, in minutes, that the user will be "leased" this dynamic IP address. After the time is up, the user will be automatically assigned a new dynamic IP address. The default is 0 minutes, which means one day.
Static DNS(1-3): The Domain Name System (DNS) is name resolution which is used to translate the names into their corresponding IP address. The DNS server is typically provided by the ISP where you subscribe the internet is.
WINS: The Windows Internet Naming Service (WINS) manages each PC's interaction with the Internet. If you use a WINS server, enter that server's IP Address here.Otherwise, leave this blank.
DHCP Reservation: Click DHCP Reservation if you want to assign a fixed local IP address to a MAC address. You will see a list of DHCP clients with the following information: Client name, Interface, IP address, and MAC address. Click the select checkbox to reserve a client's IP address. Then click Add Clients.
If you want to manually assign an IP address, enter the client's name in the Enter Client Name field. Enter the IP address you want it to have in the assign IP Address field.Make sure the IP address is between the starting DHCP server's IP address and maximum number of DHCP users range. Enter its MAC Address in the To This MAC Address field. Click Add.
- DHCP clients broadcast DHCPDISCOVER packet to the network
- DHCP server then responds with DHCPOFFER packet
- DHCP clients broadcast DHCPREQUEST packet
- DHCP server responds with DHCPACK packet
- After 50% lease time, DHCP clients will attempt to renew address with a DHCPREQUEST directed to the DHCP server
- DHCP server responds with DHCPACK adain
To configure a client to receive its IP address information from a DHCP server, the TCP/IP configuration of the computers must be configured to "obtain an IP address automatically" options. To configure the client to receive DNS options from the DHCP server, you should select the "obtain DNS server Address Automatically" option.
DHCP servers use private IP address instead of IP addresses ( registered IP address), since private IP addresses are not rout ableto the Internet, thus with the dual firewall features of the firewall will help you reduce network security threats from the Internet.
How to Configure DHCP server in Wireless Routers
Mostly all the wireless routers including the routers with build-in DSL modem or routers with build-in cable modem are powered by the DHCP server which enabled by default. So anyone that knows nothing about DHCP server, no worries - just leave the default setting.
Open the router configuration menu from the web-based utility by typing the default IP address of the wireless routers for example http://192.168.1.1 (For linksys) and press enter. The login dialog prompts you to type in the user-name and password of the router. The following table shows some wireless routers with their default IP address, user-name and password.
| Router | Address | Username | Password |
| Belkin | http://192.168.2.1 | Login | (leave blank) |
| D-Link | http://192.168.0.1 | admin | (leave blank) |
| Linksys | http://192.168.1.1 | admin | admin |
| NETGEAR | http://192.168.0.1 | admin | password |
| TRENDnet | http://192.168.10.1 | admin | admin |
Find the configuration menu with relates to DHCP menu or similar one (refer to manual book of the router). DHCP Server is enabled by factory default.If you already have a DHCP server on your network, or you don't want a DHCP server, then select disabled.
Starting IP address: Enter a value for the DHCP server to start with when issuing IP addresses. Assume the Router's default IP address is 192.168.1.1, the starting IP Address must be 192.168.1.2 or greater, but smaller than 192.168.1.253.
Maximum number of DHCP Users: Enter the Maximum number of PCs that you want the DHCP server to assign IP addresses to. This number cannot be greater than 253. The default is 50.
Client Lease Time: The Client Lease Time is the amount of time a network users will be allowed connection to the router with their current dynamic IP address. Enter the amount of time, in minutes, that the user will be "leased" this dynamic IP address. After the time is up, the user will be automatically assigned a new dynamic IP address. The default is 0 minutes, which means one day.
Static DNS(1-3): The Domain Name System (DNS) is name resolution which is used to translate the names into their corresponding IP address. The DNS server is typically provided by the ISP where you subscribe the internet is.
WINS: The Windows Internet Naming Service (WINS) manages each PC's interaction with the Internet. If you use a WINS server, enter that server's IP Address here.Otherwise, leave this blank.
DHCP Reservation: Click DHCP Reservation if you want to assign a fixed local IP address to a MAC address. You will see a list of DHCP clients with the following information: Client name, Interface, IP address, and MAC address. Click the select checkbox to reserve a client's IP address. Then click Add Clients.
If you want to manually assign an IP address, enter the client's name in the Enter Client Name field. Enter the IP address you want it to have in the assign IP Address field.Make sure the IP address is between the starting DHCP server's IP address and maximum number of DHCP users range. Enter its MAC Address in the To This MAC Address field. Click Add.
