# flush rules
iptables -F INPUT
iptables -P INPUT DROP
# allow loopback traffic
iptables -A INPUT -s lo -j ACCEPT
# allow established connections
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# allow ssh
iptables -A INPUT -s 10.15.10.0/24 -p tcp --dport 22 -j ACCEPT