To prevent arps from other interface to appear on the Internet network:
Linux will send traffic for any of it's addresses through any interface. This is allowed in rfc 1122 section 3.3.4.2. You can change this behavior by doing this:
echo 1 > /proc/sys/net/ipv4/conf/all/hidden echo 1 > /proc/sys/net/ipv4/conf/eth0/hidden echo 1 > /proc/sys/net/ipv4/conf/eth1/hidden