# iptables -A INPUT -s 65.55.44.100 -j DROP
# service iptables save
unblock :
# iptables -D INPUT -s xx.xxx.xx.xx -j DROP
# iptables -D INPUT -s 65.55.44.100 -j DROP
# service iptables save
cek config :
nano /etc/sysconfig/iptables
If you just want to block access to one port from an ip 65.55.44.100 to port 25 then type command:
# iptables -A INPUT -s 65.55.44.100 -p tcp --destination-port 25 -j DROP