For most users, who only have IPv4 at home, it's often sufficient to setup DHCP.

For example, if you have an Intel gigabit NIC, placing the following in /etc/rc.conf is sufficient.

ifconfig_em0="DHCP"

Static IP Address with hostname

defaultrouter="70.91.226.206"
hostname="[stargazer.midnightbsd.org](http://stargazer.midnightbsd.org/)"
ifconfig_ix0="70.91.226.201  netmask 255.255.255.248"

IPv6

ipv6_enable="YES"
ipv6_defaultrouter="2001:470:1f10:1c7::1"
ifconfig_em1_ipv6="inet6 2001:470:1f11:1c7::2/64"
or 
ifconfig_em1_ipv6="inet6 2001:470:1f11:1c7::2 prefixlen 64"

Some providers will give you a prefixlen 64 but a default router outside of the range. You may need to use a prefixlen 56 in this scenario. (OVH is a good example)

if you need to do a static route in IPv6:

ipv6_static_routes="ovh1"
ipv6_route_ovh1="<ip address here> -iface ix0"

Static IP alias

Add a second IP address to the same server. This can be useful for web servers, or systems with jails.

ifconfig_ix0_alias0="inet 70.91.226.202 netmask 255.255.255.255"

Stability issues

Some wired network adapters have issues with their hardware offload capabilities. Trying the following settings individually or as a group can often help.

-lro -tso -rxcsum -txcsum -txcsum6

Add these to the end of your ifconfig_em0 line...

e.g.

ifconfig_em0="DHCP -lro -tso -rxcsum -txcsum -txcsum6"

This is more likely to come up when your system is acting as a router or firewall.

Link Aggregation

For instance, you have two intel gigabit NIC ports em0 and em1

cloned_interfaces="lagg0"

ifconfig_lagg0="laggproto lacp laggport em0 laggport em1 70.91.226.201 netmask 255.255.255.248"

Add an ipv6 alias

ifconfig_lagg0_alias1="inet6 2001:4978:1fc::1/64"

WiFi

This example uses a realtek usb device

in /etc/rc.conf:

ifconfig_wlan0="WPA SYNCDHCP"

wlans_urtwn0="wlan0"

in /etc/wpa_supplicant.conf

network={
    ssid="NetworkName"
    psk="ThePassword"
}

Dual Stack

There are a few configuration options for using IPv4 and IPv6 together.

Building on the previous example,

ifconfig_em0="DHCP"
ifconfig_em0_ipv6="inet6 accept_rtadv"
rtsold_enable="YES"

This will allow anything advertising router solicitations to work. Sometimes, IPv6 uses DHCP also. This configuration will work with many setups including AWS and VMWare esxi.

Install the dual-dhclient package

mport install dual-dhclient

In /etc/rc.conf,

rtsold_enable="YES"

ifconfig_DEFAULT="SYNCDHCP accept_rtadv"

dhclient_program="/usr/local/sbin/dual-dhclient"