Dhcpcd

Dynamic Host Configuration Protocol Client Daemon (dhcpcd) is a popular DHCP client for Gentoo Linux. It is capable of handling both IPv4 and IPv6 configurations.

Emerge
Use the following command to install dhcpcd:

Files
All configuration can be set in the  file, but for most installations  will work out of the box presuming most computers nowadays are behind a router or access point running a DHCP server. Though will be helpful in case advanced configuration is required.

Static IP addresses
In case the network interface card should be configured with a static IP address, add their data to. The following is an example of manually adding a static address, routes, and DNS by editing DHCPCD's configuration file using a text editor of choice:

Run it as a service
See Network management using DHCPCD.

One-time DHCP
To configure a network interface for one-time DHCP use issue the following command:

Be sure to replace  in the command above with the appropriate network interface name.

External resources

 * Dhcpcd on the Arch Wiki