{"id":40,"date":"2017-10-10T02:51:00","date_gmt":"2017-10-10T02:51:00","guid":{"rendered":"https:\/\/linuxadmin.melberi.com\/uncategorized\/iptables-for-fedora-linux"},"modified":"2017-10-10T05:31:36","modified_gmt":"2017-10-10T05:31:36","slug":"iptables-basic-linux","status":"publish","type":"post","link":"https:\/\/www.melberi.com\/linuxadmin\/iptables\/iptables-basic-linux","title":{"rendered":"Basic Iptables Configuration for Linux"},"content":{"rendered":"

IPTABLES Basics for CentOS Fedora Linux Redhat Ubuntu Debian Linux<\/p>\n

iptables Basics<\/span><\/h3>\n
#iptables -L<\/b><\/div>\n

will list your current iptables configuration.<\/p>\n

To allow established sessions to receive traffic<\/p>\n

# iptables -A INPUT -m conntrack –ctstate ESTABLISHED,RELATED -j ACCEPT <\/b><\/p>\n

You could start by blocking traffic, but you might be working over SSH, where you would need to allow SSH before blocking everything else.<\/p>\n

To allow incoming traffic on the default SSH port (22), you could tell iptables to allow all TCP traffic on that port to come in.<\/b><\/p>\n

# iptables -A INPUT -p tcp –dport ssh -j ACCEPT<\/b><\/p>\n

Now check the current configuration<\/p>\n

# iptables -L<\/b>
\nChain INPUT (policy ACCEPT)<\/b>
\ntarget\u00a0\u00a0\u00a0\u00a0 prot opt source\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 destination<\/b>
\nACCEPT\u00a0\u00a0\u00a0\u00a0 all\u00a0 —\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 state RELATED,ESTABLISHED<\/b>
\nACCEPT\u00a0\u00a0\u00a0\u00a0 tcp\u00a0 —\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 tcp dpt:ssh <\/b><\/div>\n

For Interface based access for eth0 specify -i eth0
\nOnce we enabled the ssh port.we can drop all other incoming ports.<\/p>\n

# iptables -A INPUT -j DROP<\/b><\/p>\n

Now check the rule<\/p>\n

# iptables -L<\/b>
\nChain INPUT (policy ACCEPT)<\/b>
\ntarget\u00a0\u00a0\u00a0\u00a0 prot opt source\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 destination<\/b>
\nACCEPT\u00a0\u00a0\u00a0\u00a0 all\u00a0 —\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 state RELATED,ESTABLISHED<\/b>
\nACCEPT\u00a0\u00a0\u00a0\u00a0 tcp\u00a0 —\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 tcp dpt:ssh<\/b>
\nDROP\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 all\u00a0 —\u00a0 anywhere\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 anywhere<\/b><\/div>\n

In the final step we have to enable loopback interface. After all the traffic has been dropped. We need to insert this rule before that. Since this is a lot of traffic, we’ll insert it as the first rule so it’s processed first.<\/p>\n

#iptables -I INPUT 1 -i lo -j ACCEPT<\/b><\/p>\n

To enabling logging<\/p>\n

# iptables -I INPUT 5 -m limit –limit 5\/min -j LOG –log-prefix “iptables denied: ” –log-level 7<\/b><\/p>\n

To save this configuration<\/p>\n

# iptables-save > \/etc\/sysconfig\/iptables<\/b>
\nor<\/b>
\n#service iptables save <\/b><\/div>\n
#service iptables start<\/b><\/div>\n

This configuration will enable ssh port and disable all other incoming ports.<\/p>\n

For interface based configuration <\/a><\/p>\n

Also you can manual edit\u00a0 \/etc\/sysconfig\/iptables<\/p>\n

For Detailed Configuration<\/b><\/h4>\n","protected":false},"excerpt":{"rendered":"

IPTABLES Basics for CentOS Fedora Linux Redhat Ubuntu Debian Linux iptables Basics #iptables -L will list your current iptables configuration. To allow established sessions to receive traffic # iptables -A… Read more »<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[104],"tags":[],"class_list":["post-40","post","type-post","status-publish","format-standard","hentry","category-iptables"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t