What is Linux firewall

The concept of Iptable and usage

iptables [-t table] command [match] [target] 

In reality, for legible, we use this kind of grammar commonly. Major regulation is written by this kind of grammar, accordingly, if see the regulation that others writes, you can discover those who use also is this kind of grammar probably.
If do not want to use standard list, be about to be in [Table] place designates watch name. Not was necessary to appoint used list usually, because Iptables acquiesce uses Filter,the watch executes all orders. Also designate watch name here without necessary have to, can designate watch name in regulation anyplace almost actually. Of course, put watch name in the standard that beginning to be in had been established by usage. Although the command always is put in begin, perhaps put at the back of watch name directly, we also should be put where considering the bottom legible.
"Command " tell a program what to should do, for instance: Insert a regulation, still increase a regulation in the fine of catenary, still delete a regulation. Can careful ground introduces below.
"Match " a certain characteristic that described a package meticulously, in order to make this bag is distinguished at other all bags. Here, we can specify type of interface of the origin IP address of the bag, network, port, agreement, other perhaps what. We will see a lot of different Match below.
The target that finally is data bag is in " Target " . If data bag accords with all Match, the kernel handles it with Target, perhaps say to send the package toward Target. For instance, the other chain that we can let a kernel send the package in present list (the likelihood is ourselves build) , just perhaps discard to this is wrapped and do not do a where to manage, perhaps return to dispatcher a certain special respondent. We come to one by one discuss these option below:

Build firewall regulation with Iptables

The basic idea of Iptables and use introduced in front, we begin to use Iptables formally to found our firewall below. The method that start and stops Iptables depends on uses Linux is issued edition, you can examine the documentation of an use Linux version. In Red Hat, the Iptables that start uses:

#service Iptables Start

Usually, iptables has been included was in Linux is issued in edition, can run Iptables- - Version will examined a system to whether install Iptables. In the Fedora Core 1 that uses in me, the version of installation is Iptables V1.2.8. If your system does not have installation Iptables really, can download from the following address so: Http://www.netfilter.org/
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