RETURN: the packet is returned to the previous chain if it is a user-defined chain.QUEUE: moves the packet into the user processes requires a queue handler that forwards the packet to an application.The actions that can occur when a rule applies to the particular data packet are: These packets are handed down from rule to rule within a chain, whereby each rule can cause an action (jump target) or a change to another chain (goto chain). The tables, which are loaded with the program and previously generated by the kernel, contain chains and rules that specify how incoming and outgoing data packets should be dealt with. Iptables requires extended system privileges and can therefore be executed only as root or with appropriate administrator rights. Webmin, while operating the program via command lines is relatively uncomplicated and quick to learn. There are various graphic interfaces for iptables, e.g. We then explain the configuration of the tables by using different examples. In the following iptables tutorial, we present the basic functions and options of the packet filter software. iptables is limited to the protocol IPv4, while for other protocols there are corresponding variants, such as ip6tables for IPv6, or ebtables for Ethernet packets, which are also contained in the kernel module. With a so-called init script this is done automatically even during the boot process. The program’s tools, iptables-save and iptables-restore, are used to save and restore rule sets that have previously been set up. For the Linux kernels 2.4 and 2.6, the free software iptables is required, which was also developed by the Netfilter project team.Īs an administrator, iptables is used to set up, modify, or delete rules, while settings will be lost during the system reboot. However, an additional program is needed to configure it. In a Linux kernel, a packet filter is integrated by default, since it’s provided by modules of the software packet, Netfilter. Controlling and managing incoming and outgoing traffic – often as part of a firewall – is designed to ensure that only data packets free of malware and spam are sent and received. Packet filtering is a critical component in the security concept of all computer systems on a network.
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