Connecting to the Internet

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