add sysctl net.ipv4.conf.all.rp_filter = 1 #41
Description
We do not want to route packets from one route to another.
https://www.theurbanpenguin.com/rp_filter-and-lpic-3-linux-security/
https://wiki.archlinux.org/title/simple_stateful_firewall#Protection_against_spoofing_attacks