Where should I load iptables modules, for example ip_conntrack and ip_conntrack_ftp.

Places I have found that might be candidates, but are they?

  • The IPTABLES_MODULES variable in /etc/init.d/iptables
  • In /etc/modprobe.conf
  • In /etc/modprobe.d/xxxx.conf

None of them.

/etc/rc.d/rc.sysinit looking for two locations to load modules:

# Load other user-defined modules
for file in /etc/sysconfig/modules/*.modules ; do
  [ -x $file ] && $file

# Load modules (for backward compatibility with VARs)
if [ -f /etc/rc.modules ]; then

So, you should put the loading command into /etc/sysconfig/modules/*.modules or /etc/rc.modules:

# echo "modprobe ip_conntrack" >> /etc/sysconfig/modules/iptables.modules
# chmod +x /etc/sysconfig/modules/iptables.modules
  • Looks like you are answering all my questions. This was the general answer to my question, and @Iain had the answer to the problem I actually tried to solve.
    – Arlukin
    Nov 1 '11 at 15:01
  • For ubuntu, how can I do the same ? I need to load ip_nat_pptp module here. Jun 17 '19 at 8:17

For iptables on CentOS there is an additional location which is where I have those particular modules configured to load and that's the /etc/sysconfig/iptables-config file. The start of the file looks like this

# Load additional iptables modules (nat helpers)
#   Default: -none-
# Space separated list of nat helpers (e.g. 'ip_nat_ftp ip_nat_irc'), which
# are loaded after the firewall rules are applied. Options for the helpers are
# stored in /etc/modprobe.conf.
IPTABLES_MODULES="nf_conntrack_ftp nf_conntrack"

When I run service iptables restart I get this line

Loading additional iptables modules: nf_conntrack_ftp nf_co[  OK  ]

If I play with the contents of the

IPTABLES_MODULES="nf_conntrack_ftp nf_conntrack"

above it changes the output of the Loading additional modules line when I restart the service.

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