+`ndp`: `<boolean>` ('default =' `0`)::
+
+Enable NDP (Neighbor Discovery Protocol).
+
+`nf_conntrack_allow_invalid`: `<boolean>` ('default =' `0`)::
+
+Allow invalid packets on connection tracking.
+
+`nf_conntrack_helpers`: `<string>` ('default =' ``)::
+
+Enable conntrack helpers for specific protocols. Supported protocols: amanda, ftp, irc, netbios-ns, pptp, sane, sip, snmp, tftp
+
+`nf_conntrack_max`: `<integer> (32768 - N)` ('default =' `262144`)::