OP network design is silly and probably unjustified. No wonder he's having problems. Setting rp_filter=1 is very standard for linux routers and almost all dist

OP network design is silly and probably unjustified. No wonder he's having problems. Setting rp_filter=1 is very standard for linux routers and almost all distros set it by default. Both Debian and Red Hat set it by default. I am not sure if OP accidentally disabled this or if he is using some silly distro.