The Dynamic Host Configuration Protocol (DHCP) allows hosts on a TCP/IP network
to configure one or more network interfaces based on information collected from
a DHCP server in response to a DHCP request.
This mechanism is often used, for example, by cable modem and DSL network
providers to simplify network configurations for their clients/customers.
Information typically contained within a DHCP response includes an IP
address for the interface, subnet mask, broadcast address, router (gateway)
listing, domain name server listing, and the interface's MTU.
To set up
OpenBSD
as a DHCP client:
For each interface that is to be configured via DHCP, create a
/etc/hostname.XXX
file (where XXX is the interface's identifier, e.g., ep1) that starts with
the word
“dhcp”,
optionally followed by additional interface options.
See
hostname.if(5)
for more information on the format of these files.
The
/etc/netstart
script reads each of these hostname files at boot-time and runs the
dhclient(8)
program for each interface that is to be configured via DHCP.
[Optional] To tweak settings, edit
/etc/dhclient.conf.
This file is shipped with the system.
See
dhclient.conf(5)
and
dhclient(8)
for details.
To set up
OpenBSD
as a DHCP server:
Edit
/etc/dhcpd.conf.
This file is shipped with the system.
See
dhcpd.conf(5)
and
dhcpd(8)
for details.
Edit
/etc/rc.conf.local
and set
-dhcpd_flags="".
This will cause
OpenBSD
to start the
dhcpd(8)
daemon at boot-time and listen for DHCP requests on the local network.
To start it manually, execute the following command:
# /usr/sbin/dhcpd [netif1 netif2 ...]
The DHCP client and server use the Berkeley Packet Filter (BPF).
Ensure the kernel has been compiled with BPF support
and at least one
/dev/bpf*
file exists per broadcast network interface that is attached to the system.
This is almost always the case and should only be considered if all other
troubleshooting options have failed.
See
dhcpd(8)
for information on other available options.
Note, however, that most of the flags are useful only for debugging purposes.