Changes

[[Image:iptable-imagechains.png|thumb|600px|right|When using iptables packets must pass-through "a chain of policy rules" in order to handle packets. If a packet matches a rule, then an action is taken (some examples include: '''ACCEPT''', '''DROP'''iptables, '''REJECT''' is the one of the firewall utilities that can be used with Linux. One of the main purposes (for this course) is to use iptables for , or '''packet filteringLOG'''); otherwise, the packet will be directed to the default policy chain. ]]

Since Linux servers may be connected to the Internet, it is very important to run a firewall to control what comes into the computer system, what goes out of the computer system, and what may be forwarded to another computer. Linux uses the command A utility called '''iptables''' can be used to set the firewall ruleson a Linux server. Although graphical programs can be used  Basically, there is a list ('''chain''') of policy rules that packets must pass-through in order to configure iptableshandle packets. If a packet matches a rule, it then an action is important for students taken (some examples include: '''ACCEPT''', '''DROP''', '''REJECT''', or '''LOG'''). If the packet passes through the chain of Linux Administration to learn how rules without a match, then the packet is directed to use the iptables command default policy chain (for more complex and automated configuration via shell scriptingexample: ACCEPT, REJECT, or DROP). You can create your own customized chains (which you will learn in OPS335 course) but to keep thing simple, we only deal with 3 common predefined chains: :*'''INPUT''': Packets coming into current Linux server:*'''OUTPUT''': Packets leaving current Linux server:*'''FORWARD''': Packets being routed between Linux servers