Authored Comments

If you want to edit the rp_filter value, you should find the /etc/sysctl.conf file and add the referenced variable to that file:

echo "net.ipv4.conf.all.rp_filter = 1" >> /etc/sysctl.conf

then tell the system to reload that configuration file

sysctl -p

Once the system configuration file has the proper configuration value this setting will persist after a reboot.

While you're at it, you might want to make sure to disable source routes:
net.ipv4.conf.eth0.accept_source_route = 0
net.ipv4.conf.all.accept_source_route = 0net.ipv4.conf.default.accept_source_route = 0

the command 'sysctl -a' will give you a list of a bunch of tunable parameters and their current value.