IPv6 configuration on OpenBSD
2023-04-13T12:57:57.804Z.
This document describes the configuration of IPv6 address on OpenBSD 7.3.
IPv6 configuration via SLAAC
OpenBSD 7.3 base system comes with slaacd(8) and is enabled
by default. Add the following to the interface configuration file (e.g.
/etc/hostname.vio0):
inet6 autoconf
To apply the configurations, run:
# Change the interface name accordingly. sh /etc/netstart vio0
IPv6 static address configuration
Some ISPs or VPS service providers (e.g. OpenBSD Amsterdam, ConoHa) assign
a /64 address to the computer with information like gateway. Assume your
ISP or VPS service provider assign the IPv6 address
2606:2800:220:1::1946/64 and gateway at
2606:2800:220:1::1, add the following to the interface
configuration file (e.g. /etc/hostname.vio0):
inet6 2606:2800:220:1::1946 64
!route add -inet6 default 2606:2800:220:1::1
To apply the configurations, run:
# Change the interface name accordingly. sh /etc/netstart vio0
IPv6 configuration via DHCPv6
Some ISPs or VPS service providers assign a /64 address to the computer
using DHCPv6. OpenBSD 7.3 does not have DHCPv6 client in base system. A
third-party package dhcpcd(8) can be installed to configure
IPv6 address:
pkg_add dhcpcd
Configure dhcpcd(8) by putting a configuration file at
/etc/dhcpcd.conf. Assume only IPv6 address has to be
configured on the interface vio0, add the configuration file:
# Inform the DHCP server of our hostname for DDNS.
hostname
# Use the same DUID + IAID as set in DHCPv6 for DHCPv4 ClientID as per RFC4361.
# Some non-RFC compliant DHCP servers do not reply with this set.
# In this case, comment out duid and enable clientid above.
duid
# Persist interface configuration when dhcpcd exits.
persistent
# vendorclassid is set to blank to avoid sending the default of
# dhcpcd-<version>:<os>:<machine>:<platform>
vendorclassid
# Respect the network MTU. This is applied to DHCP routes.
option interface_mtu
# Rapid commit support.
# Safe to enable by default because it requires the equivalent option set
# on the server to actually work.
option rapid_commit
# A ServerID is required by RFC2131.
require dhcp_server_identifier
# generate Stable Private IPv6 Addresses based from the DUID
slaac private
# Apply IPv6 configurations only.
ipv6only
# Configuure specific interfaces only.
allowinterfaces vio0
Enable and start dhcpcd(8):
rcctl enable dhcpcd rcctl start dhcpcd
Verification
Use ifconfig(8) to check the IPv6 address assigned to the
network interface and route(8) to check the routing tables.
To check if the computer can reach the Internet over IPv6, run:
ping6 -c 3 example.com
The output should be similar to the following:
PING example.com (2606:2800:220:1:248:1893:25c8:1946): 56 data bytes 64 bytes from 2606:2800:220:1:248:1893:25c8:1946: icmp_seq=0 hlim=57 time=103.895 ms 64 bytes from 2606:2800:220:1:248:1893:25c8:1946: icmp_seq=1 hlim=57 time=103.952 ms 64 bytes from 2606:2800:220:1:248:1893:25c8:1946: icmp_seq=2 hlim=57 time=103.922 ms --- example.com ping statistics --- 3 packets transmitted, 3 packets received, 0.0% packet loss round-trip min/avg/max/std-dev = 103.895/103.923/103.952/0.024 ms