Block an IP using iptables

To block an IP using iptables, use

iptables -A INPUT -s IPADDR -j DROP

Replace IPADDR with IP address you need to block.

To block an IP range

iptables -A INPUT -s IP_IN_CIDR_FORMAT -j DROP

Example, bock IP range 159.138.0.0/16

iptables -A INPUT -s 159.138.0.0/16 -j DROP

Unblock an IP address

To unblock an IP address, first find the rule number, you can do it with the command

iptables --list  INPUT -n --line-number | grep IP_ADDR_HERE

Once you find the number of rule to be removed, you can run

iptables --delete INPUT RULE_NUMBER_HERE

Example

iptables delete a rule