Se­cu­rity ta­ble

OpenSource For You - - ADMIN -

In­put: Ap­plies to net­work pack­ets tar­geted for the host. Out­put: Ap­plies to lo­cally-gen­er­ated net­work pack­ets be­fore they are sent out. For­ward: Ap­plies to net­work pack­ets routed through the host. Ev­ery net­work packet re­ceived by or sent from a Linux sys­tem is sub­ject to at least one ta­ble. How­ever, a packet may be sub­jected to mul­ti­ple rules within each ta­ble be­fore emerg­ing at the end of the chain. The struc­ture and pur­pose of these rules may vary, but they usu­ally seek to iden­tify a packet com­ing from or go­ing to a par­tic­u­lar IP ad­dress, or set of ad­dresses, when us­ing a par­tic­u­lar pro­to­col and net­work service. Fig­ure 1 out­lines how the flow of pack­ets is

In this ex­am­ple, we changed the name of the chain from al­lowed to dis­al­lowed.

-F: Flushes the se­lected chain, which ef­fec­tively deletes ev­ery rule in the chain. If no chain is spec­i­fied, this com­mand flushes ev­ery rule from ev­ery chain.


-h: Pro­vides a list of com­mand struc­tures, as well as a quick sum­mary of com­mand pa­ram­e­ters and op­tions.

-I [<in­te­ger>]: Inserts the rule in the spec­i­fied chain at a point spec­i­fied by a user-de­fined in­te­ger ar­gu­ment. If no ar­gu­ment is spec­i­fied, the rule is in­serted at the top of the chain.

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