Moxa Technologies UC-7420/7410 Observe and erase chain rules, Define policy for chain rules

UC-7420/7410 User’s Manual Managing Communication

The basic syntax to enable and load an IPTABLES module is as follows:

#lsmod

#modprobe ip_tables #modprobe iptable_filter

Use lsmod to check if the ip_tables module has already been loaded in the UC-7420/7410. Use modprobe to insert and enable the module.

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

#modprobe iptable_filter

Use iptables, iptables-restore, iptables-save to maintain the database.

NOTE IPTABLES plays the role of packet filtering 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

Since the IPTABLES command is very complex, 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]: List List 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

Define policy for chain rules

Usage:

#iptables [-t tables] [-P] [INPUT, OUTPUT, FORWARD, PREROUTING, OUTPUT, POSTROUTING] [ACCEPT, DROP]

-P:	Set the policy for the chain to the given target.
INPUT:	For packets coming into the UC-7420/7410.

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