Moxa RM-2600-T [31/52] Define policy for chain rules

Moxa RM-2600-T [31/52] Define policy for chain rules
ioPAC RTU Software RTU Communications
4-6
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 ioPAC RTU.
OUTPUT: For locally-generated packets.
FORWARD: For packets routed out through the ioPAC RTU.
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 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 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 W341’s port 137, 138, 139
# iptables A INPUT i eth0 p tcp s 192.168.0.24 --dport 137:139 j ACCEPT

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