Introduction
It is sometimes useful to connect the experiment network to the Internet to install software or access external resources. This article describes the simple case of connecting a single VM to the Internet. With minor changes, this technique can also be used to connect an entire experiment to the Internet if the single VM acts as a router.
Single VM
The VM must be configured with at least one network interface:
vm config net LAN
To connect this interface to the Internet, we setup a NAT on the host machine by creating a tap:
tap create LAN ip 10.0.0.1/24 nat0
Enabling IP forwarding on the host machine:
bash$ sysctl -w net.ipv4.ip_forward=1
And configuring iptables to enable the NAT on the host machine:
bash$ iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE bash$ iptables -A INPUT -i nat0 -j ACCEPT bash$ iptables -A INPUT -i eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT bash$ iptables -A OUTPUT -j ACCEPT
You may need to change eth0 to match the interface on the host machine with Internet access.
On the VM, we would then configure a static IP of 10.0.0.2/24, using 10.0.0.1 as the default gateway. On Linux this can be achieved with the following:
ip addr add 10.0.0.2/24 dev eth0 ip route add default via 10.0.0.1
You may also need to configure DNS on the VM.
Authors
The minimega authors
3 July 2018