changing Kernal parameters for security reasons.

Disable Source Routing:

The kernel parameter net.ipv4.conf.all.accept_source_route must be set to "0" (zero) to disallow source routing.

IP Forwarding:

The kernel parameter net.ipv4.ip_forward must be set to "0" (zero) to disallow IP Forwarding.

ICMP Broadcast Response:

The kernel parameter icmp_echo_ignore_broadcasts must be set to "1" (one).

Syn Flood Protection:

The kernel parameter net.ipv4.tcp_syncookies must be set to "1" (one) in order to defend against Syn Flood attacks .

Reverse Path Filter:

The kernel parameter net.ipv4.conf.all.rp_filter must be set to “1” so that the network subsystem will validate source addresses against the Routing Table.

Accepting ICMP redirects:

The kernel parameter net.ipv4.conf.default.accept_redirects must be set to “0” so that the network subsystem will not accept ICMP redirects.

Sending ICMP Redirects

The kernel parameters net.ipv4.conf.all.send_redirects and net.ipv4.conf.default.send_redirects must both be set to “0” so that the network subsystem will not send out ICMP redirects.