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UC-7420/7410 User’s Manual Managing Communication
4-9
OUTPUT: For locally-generated packets.
FORWARD: For packets routed out through the UC-7420/7410.
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
#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.
Append or delete rules:
Usage:
# iptables [-t table] [-AI] [INPUT, OUTPUT, FORWARD] [-io interface] [-p tcp, udp, icmp,
all] [-s IP/network] [--sport ports] [-d IP/network] [--dport ports] –j [ACCEPT. DROP]
-A: Append one or more rules to the end of the selected chain.
-I: Insert one or more rules in the selected chain as the given rule number.
-i: Name of an interface via which a packet is going to be received.
-o: Name of an interface via which a packet is going to be sent.
-p: The protocol of the rule or of the packet to check.
-s: Source address (network name, host name, network IP address, or plain IP address).
--sport: Source port number.
-d: Destination address.
--dport: Destination p ort number.
-j: Jump target. Specifies the target of the rules; i.e., how to handle matched packets.
For example, ACCEPT the packet, DROP the packet, or LOG the packet.
Examples:
Example 1: Accept all packets from lo interface.
# iptables –A INPUT –i lo –j ACCEPT
Example 2: Accept TCP packets from 192.168.0.1.
# iptables –A INPUT –i ixp0 –p tcp –s 192.168.0.1 –j ACCEPT
Example 3: Accept TCP packets from Class C network 192.168.1.0/24.
# iptables –A INPUT –i ixp0 –p tcp –s 192.168.1.0/24 –j ACCEPT
Example 4: Drop TCP packets from 192.168.1.25.
# iptables –A INPUT –i ixp0 –p tcp –s 192.168.1.25 –j DROP
Example 5: Drop TCP packets addressed for port 21.
# iptables –A INPUT –i ixp0 –p tcp --dport 21 –j DROP
Example 6: Accept TCP packets from 192.168.0.24 to UC-7420/7410’s port 137, 138, 139
# iptables –A INPUT –i ixp0 –p tcp –s 192.168.0.24 --dport 137:139 –j ACCEPT
Example 7: Log TCP packets that visit UC-7420/7410’s port 25.
# iptables –A INPUT –i ixp0 –p tcp --dport 25 –j LOG
Example 8: Drop all packets from MAC address 01:02:03:04:05:06.
# iptables –A INPUT –i ixp0 –p all –m mac –mac-source 01:02:03:04:05:06 –j DROP
NOTE: In Example 8, remember to issue the command
#modprobe ipt_mac
first to load module
ipt_mac.