https://tldp.org/HOWTO/Adv-Routing-HOWTO/lartc.rpdb.multiple-links.html
https://unix.stackexchange.com/questions/23820/what-is-the-routing-behaviour-when-two-or-more-default-routes
https://www.rogerperkin.co.uk/network-automation/python/scripts-for-network-engineers/