If packets are leaking from a host-only network on a Linux host system, packet forwarding might be mistakenly enabled on the host system. If packet forwarding is enabled, you must disable it.

How you disable packet forwarding depends on your Linux distribution. For example, you might be able to use a control panel, specify a setting at the time you compile your kernel, or enter a specification when you boot your system. See the operating system documentation for more information.

As root, write a 0 (zero) to the special file /proc/sys/net/ipv4/ip_forward.

echo "0" > /proc/sys/net/ipv4/ip_forward