Setting up networking on OpenBSD hosted VMs

Quick tutorial on networking OpenBSD VMs

Posted on Sat, 14 Nov 2015 12:00:00 MST by Aaron Bieber

Tags: OpenBSD

With OpenBSD getting a native hypervisor, I figured I would quickly describe my setup for allowing the VMs to access network resources!

This setup is using NAT and IP forwarding.

First thing, enable forwarding:

doas echo "net.inet.ip.forwarding=1" >> /etc/sysctl.conf 
# Only run the above if you want this all to start at boot
sysctl net.inet.ip.forwarding=1

Next we need to configure a tap interface at tap0.

cat /etc/hostname.tap0:

inet 10.10.10.1 255.255.255.0
up

Now tell pf what to do with the packets coming from the tap0 interface:

match out on $ext_if inet from tap0:network nat-to ($ext_if)

At this point, you could just manually assign ips to your VMs when booting / installing.

For a bit more automation, we can run dhcpd on the tap0 interface: cat /etc/dhcpd.conf

option  domain-name "vm.bolddaemon";
option  domain-name-servers 8.8.8.8, 8.8.4.4;

subnet 10.10.10.0 netmask 255.255.255.0 {
	option routers 10.10.10.1;
	range 10.10.10.5 10.10.10.30;
}

Pretty nifty, and all of it is in base (on amd64 and i386)!!

Notes

Setting up networking on OpenBSD hosted VMs