Delete iptables rules-how to delete an existing iptables rule

Syntax: iptables-Dchainrulenum [options] Where: chain indicates the chain, that is, the attribute rulenum such as INPUTFORWARD indicates the rule number. Start from 1. You can use iptables-LINPUT -- line-numbers to list... syntax: iptables-D chain rulenum [options] Where: chain indicates the chain, that is, the attribute rulenum such as input forward is the number of the rule. Start from 1. You can use iptables-l input -- line-numbers to list the rule numbers of the specified chain. Therefore, for example, if you want to delete an INPUT chain rule, iptables-d input 3 means to delete 3rd rules. There is also A second method. The second method is-A command ing, but replace-A with-D. This is useful when the rules in your chain are complex and you do not want to calculate their numbers. That is to say, how do you use iptables-.... if A rule is defined in A statement,-D is used to replace-A directly when this rule is deleted. The rest will remain unchanged without any numbers. ==================================== Let's talk about the preceding -- line-numbers option, the following command: iptables-l input -- line-numbers lists all rules of the INPUT chain num target prot opt source destination 1 REJECT tcp -- anywhere tcp dpt: microsoft-ds reject-with icmp-port-unreachable 2 REJECT tcp -- anywhere tcp dpt: 135 reject-with icmp-port-unreachable 3 REJECT tcp -- anywhere tcp dpt: netbios-ssn reject-with icmp-port-unreachable 4 REJECT udp -- anywhere udp dpt: microsoft-ds reject-with icmp-port-unreachable 5 REJECT udp -- anywhere udp dpt: 135 reject-with icmp-port-unreachable ...... delete the specified row 4th rule: iptables-d input 4 [root @ tp ~] # Iptables-F clear the rules of all rule chains in the filter of the preset table [root @ tp ~] # Iptables-X clear the rules in the user-defined chain in the filter of the preset table