IPTables In Linux Explained
IPtables (Netfilter) :IPtables is the default firewall for Linux. Its a vast subject which can not be covered in one post. I will try to give as much info as possible at the same time not to make it complex. Lets start with basics. What is a firewall?Ans : A firewall is a part of a computer system or network that is designed to block unauthorized access while permitting authorized communications –Wikipedia.orgA IPtables firewall contains tables which in tern contains rules to block or unblock a perticular communication.A table can be a1.Filter table — Used to filter packets.2.NAT(Network Adress Translator) table — Used for NATing of source and destination ip address(Used for sharing internet)3.Mangale table — Its a combination of Filter and NAT tables4.RAW table — Used to for marking packets not to track. 1.Filter table : This is the default table which contaions three chains.a.INPUT Chain : To apply a rule on packets which are coming into the system.b.FORWARD Chain : For packets being routed through the systemc.OUTPUT Chain : For packets locally generated which are going out from the system.2.NAT table : This table is having three chains.a.PREROUTING Chain : For altering the packets as soon as they come in to the systemb.OUTPUT Chain : For packets locally generated which are going out from the system.c.POSTROUTING Chain : For altering the packets which are about to go...
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