The iptables Rules changes using CLI commands will be lost upon system reboot. For example, if the INPUT policy is DROP or REJECT and the Rules are flushed, all incoming traffic will be dropped or rejected and network communication broken. Specifying a is optional without a chain specification, all chains are flushed.Įxample to flush Rules in the OUTPUT ~]# iptables -F OUTPUTīe aware of the default chain policy. To flush or clear iptables Rules, use the -flush, -F option : Target prot opt source destination Flushing Rules The following replaces this Rule, restricting connections to the standard http port (port 80) only from the network address range ~]# iptables -R INPUT 1 -p tcp -s 192.168.0.0/24 -dport 80 -j ~]# iptables -LĪCCEPT tcp - 192.168.0.0/24 anywhere tcp dpt:http In the example shown previously, the first Rule given allows connections to the http port (port 80) from anywhere. Rules may be specified to replace existing Rules in the chain. Afterward, the existing Rule will then be in the fourth position in the chain. So, for example, if you want to insert a Rule before the third rule you specify the number 3. The number given after the chain name indicates the position before an existing Rule. Target prot opt source destination Inserting RulesĬreate a Rule at the top (first) ~]# iptables -I INPUT 1 -p tcp -dport 80 -j ~]# iptables -L The following example deletes an existing Rule created earlier that is currently in the fifth ~]# iptables -D INPUT ~]# iptables -L To delete a Rule, you must know its position in the chain. The following adds a Rule at the end of the specified chain of ~]# iptables -A INPUT -p tcp -dport 80 -j ~]# iptables -LĪCCEPT tcp - anywhere anywhere tcp dpt:http Therefore, for example, if a Rule rejecting ssh connections is created, and afterward another Rule is specified allowing ssh, the Rule to reject is applied and the later Rule to accept the ssh connection is not. Note that Rules are applied in order of appearance, and the inspection ends immediately when there is a match. To include matching counters, include -v argument.Įxample of iptables Rules allowing any connections already established or related, icmp requests, all local traffic, and ssh ~]# iptables -LĪCCEPT all - anywhere anywhere state RELATED,ESTABLISHEDĪCCEPT tcp - anywhere anywhere state NEW tcp dpt:ssh Rules listed with the -L command option do not include matching counters.
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