How To: Whitelist An IP Address In IPTables

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Most Linux distributions will use IPTables as the default firewall.

Here are the commands to whitelist an IP address on your Linux server, both incoming and outgoing.

Example: How to whitelist IP address 192.168.0.1

Step 1: Log into the server via SSH.

Step 2: Allow incoming connections from 192.168.0.1

# iptables -A INPUT -s 192.168.0.1 -j ACCEPT

Step 3: Allow outgoing connections to 192.168.0.1

# iptables -A OUTPUT -d 192.168.0.1 -j ACCEPT

 

Additional Options:

You can specify the destination port using the --dport option.

You can specify the protocol using the -p option

You can specify the interface using the -i option for input, and the -o option for output

i.e. 

# iptables -A INPUT -s 192.168.0.1 -p tcp --dport 80 -i eth0 -j ACCEPT

This will allow connections from source 192.168.0.1 only on port 80, only on any IP address associated with
eth0, only using TCP protocol.

# iptables -A OUTPUT -d 192.168.0.1 -p tcp --dport 443 -o eth0 -j ACCEPT

This will allow outgoing connections to destination IP 192.168.0.1 using protocol TCP,
only on destination port 443, only from the interface eth0.

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