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Configure Network on OpenBSD

Introduction

I won't go into too much detail, as that's what the OpenBSD website is for. This is just a quick reference for recalling how to rapidly configure networking.

Basic Configuration

ifconfig

To list available network cards and view defined IP addresses:

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$ ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 33224
        inet 127.0.0.1 netmask 0xff000000
        inet6 ::1 prefixlen 128
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x5
lo1: flags=8008<LOOPBACK,MULTICAST> mtu 33224
fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        address: 00:04:ac:dd:39:6a
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        inet 10.0.0.38 netmask 0xffffff00 broadcast 10.0.0.255
        inet6 fe80::204:acff:fedd:396a%fxp0 prefixlen 64 scopeid 0x1
pflog0: flags=0<> mtu 33224
pfsync0: flags=0<> mtu 2020
sl0: flags=c010<POINTOPOINT,LINK2,MULTICAST> mtu 296
sl1: flags=c010<POINTOPOINT,LINK2,MULTICAST> mtu 296
ppp0: flags=8010<POINTOPOINT,MULTICAST> mtu 1500
ppp1: flags=8010<POINTOPOINT,MULTICAST> mtu 1500
tun0: flags=10<POINTOPOINT> mtu 3000
tun1: flags=10<POINTOPOINT> mtu 3000
enc0: flags=0<> mtu 1536
bridge0: flags=0<> mtu 1500
bridge1: flags=0<> mtu 1500
vlan0: flags=0<> mtu 1500
        address: 00:00:00:00:00:00
vlan1: flags=0<> mtu 1500
        address: 00:00:00:00:00:00
gre0: flags=9010<POINTOPOINT,LINK0,MULTICAST> mtu 1450
carp0: flags=0<> mtu 1500
carp1: flags=0<> mtu 1500
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
gif1: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
gif2: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
gif3: flags=8010<POINTOPOINT,MULTICAST> mtu 1280

Here's a listing of available interfaces with their explanations:

  • lo - Loopback Interface
  • pflog - Packet Filter Logging Interface
  • sl - SLIP Network Interface
  • ppp - Point to Point Protocol
  • tun - Tunnel Network Interface
  • enc - Encapsulating Interface
  • bridge - Ethernet Bridge Interface
  • vlan - IEEE 802.1Q Encapsulation Interface
  • gre - GRE/MobileIP Encapsulation Interface
  • gif - Generic IPv4/IPv6 Tunnel Interface
  • carp - Common Address Redundancy Protocol Interface

Setting a Permanent IP

Simply create a file /etc/hostname.interface_name and insert the IP and subnet mask:

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echo "inet 172.16.1.100 255.255.255.0 NONE" > /etc/hostname.fxp0

Default Gateway

To set your default gateway (or default route), create the file /etc/mygate and specify the desired IP:

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echo "172.16.1.254" > /etc/mygate

DNS

To set DNS servers, it's quite simple, as in all Unix-like systems, edit the resolv.conf file:

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search example.com
nameserver 125.2.3.4
nameserver 125.2.3.5

Hostname

To define a machine's hostname, simply insert the desired name in the /etc/myname file:

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echo "server" > /etc/myname

Applying Changes Without Rebooting

Obviously, you don't need to restart the machine, but you do need to restart the network services! To restart network services:

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$ sh /etc/netstart
writing to routing socket: File exists
add net 127: gateway 127.0.0.1: File exists
writing to routing socket: File exists
add net 224.0.0.0: gateway 127.0.0.1: File exists

Routes

To display routes:

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route show

or

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netstat -rn

Finally, to add static routes, here's an example of an /etc/hostname.if file (adapt to your needs):

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inet 192.168.254.254 255.255.255.0 NONE !
route add 10.0.0.0 192.168.254.1

Network Tuning

Improving Performance on High Bandwidth

If you want to increase bandwidth performance, you can activate it via sysctl. To test temporarily:

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sysctl net.inet.tcp.recvspace=65536
sysctl net.inet.tcp.sendspace=65536

To make it permanent, add these lines to /etc/sysctl.conf:

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echo "# Increase performance" >> /etc/sysctl.conf
echo "net.inet.tcp.recvspace=65536" >> /etc/sysctl.conf
echo "net.inet.tcp.sendspace=65536" >> /etc/sysctl.conf

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