DA-681 Linux
Managing Communications
3-13
--sport: Source port number.
-d: Destination address.
--dport: Destination port 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 the lo interface.
# iptables –A INPUT –i lo –j ACCEPT
Example 2: Accept TCP packets from 192.168.0.1.
# iptables –A INPUT –i eth0 –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 eth0 –p tcp –s 192.168.1.0/24 –j ACCEPT
Example 4: Drop TCP packets from 192.168.1.25.
# iptables –A INPUT –i eth0 –p tcp –s 192.168.1.25 –j DROP
Example 5: Drop TCP packets addressed for port 21.
# iptables –A INPUT –i eth0 –p tcp --dport 21 –j DROP
Example 6: Accept TCP packets from 192.168.0.24 to DA-681-I-LX’s port 137, 138, 139
# iptables –A INPUT –i eth0 –p tcp –s 192.168.0.24 --dport 137:139 –j ACCEPT
Example 7: Log TCP packets that visit DA-681-I-LX’s port 25.
# iptables –A INPUT –i eth0 –p tcp --dport 25 –j LOG
Example 8: Drop all packets from MAC address 01:02:03:04:05:06.
# iptables –A INPUT –i eth0 –p all –m mac --mac-source 01:02:03:04:05:06 –j DROP
ATTENTION
In Example 8, remember to issue the command # modprobe ipt_mac first to load the module ipt_mac.
NAT (Network Address Translation)
The NAT (Network Address Translation) protocol translates IP addresses used on one network into IP addresses
used on a connecting network. One network is designated the inside network and the other is the outside
network. Typically, the DA-681-LX connects several devices on a network and maps local inside network
addresses to one or more global outside IP addresses, and un-maps the global IP addresses on incoming
packets back into local IP addresses.
ATTENTION
Click on the following links for more information about NAT.
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http://www.netfilter.org/documentation/HOWTO//packet-filtering-HOWTO.html
