Moxa RM-1050-T — основы работы с iptables: управление правилами фильтрации [30/52]

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Use the following command to load the modules (iptable_filter, iptable_mangle, iptable_nat):

#modprobe iptable_filter

NOTE

iptables

plays the role of packet filter or NAT. Take care when setting up the iptables

rules. If the rules are

not correct, remote hosts that connect via a LAN or PPP may be denied access. We recommend using the serial

console to

set up the iptables.

Click on the following links for

more information about iptables:

http://www.linuxguruz.com/iptables/

http://www.netfilter.org/documentation/HOWTO//packet

-filtering-HOWTO.html

To illustrate the iptables syntax, we have divided our discussion of the various rules into three categories:

observe and erase chain rules, define policy rules, and append or delete rules.

Observe and Erase Chain Rules

Usage:

# iptables [-t tables] [-L] [-n]

-t tables: Table to manipulate (default: ‘filter’); example: nat or filter.

-L [chain]: Lists all rules in selected chains. If no chain is selected, all chains are listed.

-n: Numeric output of addresses and ports.

# iptables [-t tables] [-FXZ]

-F: Flush the selected chain (all the chains in the table if none is listed).

-X: Delete the specified user-defined chain.

-Z: Set the packet and byte counters in all chains to zero.

Examples:

# iptables -L -n

In this example, since we do not use the -t parameter, the system uses the default ‘filter’ table. Three

chains are included: INPUT, OUTPUT, and FORWARD. INPUT chains are accepted automatically, and all

connections are accepted without being filtered.

#iptables –F

#iptables –X

#iptables –Z