Static DHCP

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Revision as of 23:36, 1 March 2006 by 72.128.92.130 (Talk)
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What is Static DHCP?

This is a very useful feature which makes the DHCP server on your router always assign the same IP address to a specific computer on your LAN. To be more specific the DHCP server assigns the IP to the network card of your computer. Every network card has its unique address - the so called MAC address (MAC = media access control).


Why would I need Static DHCP?

You will need this if you want your computer to always have the same IP address. This is useful if other people on your LAN know your IP and access your PC using this IP. Another important use is, when you do port forwarding. If you forward a WAN port to a port on a server running on your LAN you have to give that server a static IP that does not change.

How does static IP address assignment work?

Your computer boots and requests its IP from the router's DHCP server. The DHCP server recognizes the MAC address of your PC and assigns the static IP address to it.


How to set up static DHCP assignment

Go to Administration -> Management (in DD-WRT v23 : Administration -> Services)

Enable Dhcpd under "Static Allocations". Add the desired DHCP static IP assignments.


Explanation of Dhcpd options

The dhcp system assigns IP addresses to your local devices. While the main configuration is on the setup page you can program some nifty special functions here.

Dhcpd: Disabling here will disable dhcp on this router irrespective of the settings on the Setup screen.

Used domain: You can select here which domain the DHCP clients should get as their local domain. This can be the WAN domain set on the Setup screen or the LAN domain which can be set here.

LAN Domain: You can define here your local LAN domain which is used as local domain for DNSmasq and DHCP service if chosen above.

Static allocations: If you want to assign certain hosts a specific address then you can define them here. This is also the way to add hosts with a fixed address to the router's local DNS service (DNS masq).

The format for static allocations is:

<IP Address>  <##:##:##:##:##:##>  <Hostname>

Warning: Be sure to set your static IPs outside of your automatic DHCP address range. This range is 192.168.1.100-192.168.1.149 by default and can be configured on the Setup screen.

Also note: Make sure you do not have a blank set of fields (MAC, HOST, & IP). This will cause an error "is not a valid MAC address" because you left a MAC address field empty.

Example

In DD-WRT v23:

To assign the IP address 192.168.1.12 and the hostname "mypc" to a PC with a network card having the MAC address 00:AE:0D:FF:BE:56 you should press Add then enter 00:AE:0D:FF:BE:56 into the MAC field, mypc into the HOST field and 192.168.1.12 into the IP field.

After each entry press Save Settings (at the bottom of the Services page).

To add an additional entry, press Add again.