UC-8100-LX Software Manual
General Debian Package Usage
5-10
-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
97B
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-8100-LX series.
OUTPUT:
For locally-generated packets.
FORWARD:
For packets routed out through the UC-8100-LX series.
PREROUTING:
To alter packets as soon as they come in.
POSTROUTING: To alter packets as they are about to be sent out.
Examples:
#iptables –P INPUT DROP
#iptables –P OUTPUT ACCEPT
#iptables –P FORWARD ACCEPT
# modprobe iptable_nat
#iptables –t nat –P PREROUTING ACCEPT
#iptables –t nat –P OUTPUT ACCEPT
#iptables -t nat –P POSTROUTING ACCEPT
In this example, the policy accepts outgoing packets and denies incoming packets.