dhcp - configuring OpenBSD for DHCP
The Dynamic Host Configuration Protocol (DHCP) allows hosts
on a TCP/IP
network to configure one or more network interfaces based on
collected from a DHCP server in response to a DHCP request.
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,
listing, domain name server listing, and the interface's
To set up OpenBSD as a DHCP client:
1. 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
followed by additional interface options. See
for more information on the format of these
The /etc/netstart script reads each of these
hostname files at
boot-time and runs the dhclient(8) program for
that is to be configured via DHCP.
2. [Optional] To tweak settings, edit
file is shipped with the system. See
dhclient(8) for details.
To set up OpenBSD as a DHCP server:
1. Edit /etc/dhcpd.conf. This file is shipped with
See dhcpd.conf(5) and dhcpd(8) for details.
2. Edit /etc/dhcpd.interfaces. This file should
contain a list
of interfaces you wish to serve by dhcpd(8). If
you have only
one broadcast network interface or you wish to
serve all interfaces,
this step is not required. Be sure to
file empty (or even delete it) if this is the
3. Edit /etc/rc.conf.local and set dhcpd_flags="-q".
cause OpenBSD to start the dhcpd(8) daemon at
listen for DHCP requests on the local network.
To start it
manually, execute the following commands:
# touch /var/db/dhcpd.leases
# /usr/sbin/dhcpd -q [netif1 netif2 ...]
4. Ensure the kernel has been compiled with BPF
Filter) support and at least one /dev/bpf* file
broadcast network interface that is attached to
This is almost always the case and should only be
if all other troubleshooting options have failed.
See dhcpd(8) for information on other available options.
that most of the flags are useful only for debugging purposes.
/etc/dhcpd.conf DHCP server configuration file
/etc/dhcpd.interfaces list of network interfaces served by
/etc/rc.conf.local configuration file where dhcpd_flags
must be set
/etc/dhclient.conf DHCP client configuration file
/etc/hostname.XXX interface-specific configuration
dhclient.conf(5), dhcpd.conf(5), hostname.if(5),
OpenBSD 3.6 July 8, 1999
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