#!/bin/sh
# Assuming you want to make a random private /120 prefix in IP and have all of
# those addresses assigned to the loopback interface (dev lo), and you're root,
# and have https://gitlab.com/ipcalc/ipcalc installed, and aren't in a network
# namespace other than global, run:
#
# If you also want to be able to bind to those IP addresses, run the following command:
# sysctl -w net.ipv6.ip_nonlocal_bind = 1
#
#
# IPv4 is obsolete, so IP in this document means IPv6
#
# ~jmjl

# Sets NETWORK and PREFIX with the random network
# and 120, which is the prefix we have hardcoded in this line.
eval "$(ipcalc -r 120 -np)"

# Making it such that netpref is the network + prefix so we can give it to ip
netpref="${NETWORK}/${PREFIX}"

# Adds the address to the loopback interface lo, and sets scope to host as this
# IP will only be valid inside this host
ip addr add "$netpref" dev lo scope host

# Adds a route so that traffic going to the IP range will go to the local
# machine
ip route add local "$netpref" dev lo