{"id":1903,"date":"2018-10-28T14:45:00","date_gmt":"2018-10-28T14:45:00","guid":{"rendered":"https:\/\/www.appservgrid.com\/paw92\/?p=1903"},"modified":"2018-10-31T03:09:39","modified_gmt":"2018-10-31T03:09:39","slug":"iptables-introduction-and-examples-linuxadmin-io","status":"publish","type":"post","link":"https:\/\/www.appservgrid.com\/paw92\/index.php\/2018\/10\/28\/iptables-introduction-and-examples-linuxadmin-io\/","title":{"rendered":"Iptables Introduction and Examples – LinuxAdmin.io"},"content":{"rendered":"

Iptables is a firewall service included in CentOS, in CentOS 7 its offered as a alternative firewalld is offered as well. Iptables uses netfilter to filter chains. Essentially you create a chain of filter rules to process how incoming and outgoing data is handled. You can view more about iptables on Netfilter<\/a><\/p>\n

Iptables rule format<\/h2>\n

The iptables rules format is pretty simplistic when using basic rules to allow or deny traffic.<\/p>\n

iptables -t <type> <direction> <pattern> -j <action><\/p>\n

Type<\/h3>\n

for -t <type> there are two basic type options filter and nat<\/p>\n

filter \u2013 creates a rule for filtering traffic.
\nnat \u2013 this creates a nat(network address translation) rule.<\/p>\n

Direction<\/h3>\n

\u2013append \u2013 Adds a rule to the end of the chain. You also want to specify INPUT (incoming packets) or OUTPUT (outgoing packets) when appending rules.
\n\u2013delete \u2013 Deletes a rule from the chain. You also want to specify INPUT (incoming packets) or OUTPUT (outgoing packets) when deleting rules.
\n\u2013list \u2013 lists the current rules
\n\u2013flush \u2013 flushes all the rules<\/p>\n

Pattern<\/h3>\n

\u2013source <ip_address> \u2013 Rule only applies to packets coming from this source IP address.
\n\u2013destination <ip_address> \u2013 Rule only applies for packets going to this destination IP address.<\/p>\n

Action<\/h3>\n

DROP \u2013 packets are dropped
\nREJECT \u2013 packets are dropped and a error message sent back
\nACCEPT \u2013 packets are allowed<\/p>\n

Iptables Service Management<\/h2>\n

How to manage the IPtables service itself.<\/p>\n

To start iptables:<\/h4>\n

service iptables start<\/p>\n

To stop iptables:<\/h4>\n

service iptables stop<\/p>\n

To ensure iptables starts on reboot:<\/h4>\n

CentOS 6:<\/p>\n

chkconfig –add iptableschkconfig iptables on<\/p>\n

Centos 7:<\/p>\n

systemctl enable iptables<\/p>\n

Restore saved ruleset:<\/h4>\n

iptables-restore < \/etc\/sysconfig\/iptables<\/p>\n

Save new rules permamently:<\/h4>\n

iptables-save > \/etc\/sysconfig\/iptables<\/p>\n

Example rules:<\/h3>\n

Samples of different functions you can perform to block or accept traffic based on IP addresses and Ports.<\/p>\n

Block a IP with Iptables:<\/p>\n

iptables -A INPUT -s 1.2.3.4 -j DROP<\/p>\n

Allow a IP<\/p>\n

iptables -A INPUT -s 1.2.3.4 -j ACCEPT<\/p>\n

Block a PORT:<\/p>\n

iptables -A INPUT -p tcp –dport 21 -j DROP<\/p>\n

Allow a IP to a specific port:<\/p>\n

iptables -A INPUT -s 1.2.3.4 -p tcp –dport 21 -j ACCEPT<\/p>\n

There is much more that you can do with iptables this is just a basic introduction.<\/p>\n

Source<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Iptables is a firewall service included in CentOS, in CentOS 7 its offered as a alternative firewalld is offered as well. Iptables uses netfilter to filter chains. Essentially you create a chain of filter rules to process how incoming and outgoing data is handled. You can view more about iptables on Netfilter Iptables rule format … <\/p>\n

Continue reading “Iptables Introduction and Examples – LinuxAdmin.io”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1903","post","type-post","status-publish","format-standard","hentry","category-linux"],"_links":{"self":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/1903","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/comments?post=1903"}],"version-history":[{"count":1,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/1903\/revisions"}],"predecessor-version":[{"id":2026,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/1903\/revisions\/2026"}],"wp:attachment":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/media?parent=1903"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/categories?post=1903"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/tags?post=1903"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}