1、First you have to make sure your NanoPi M3 can work access to the Internet；
2、And you need to install iptables in nanopi m3：
#apt-get install iptables
3、Check the current Iptables information of NanoPi M3 configuration：
#iptables -L
4、Configure /etc/iptables.test.rules：
#vi /etc/iptables.test.rules
<br>*filter
# Allows all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
-A INPUT -i lo -j ACCEPT
-A INPUT ! -i lo -d 127.0.0.0/8 -j REJECT
# Accepts all established inbound connections
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# Allows all outbound traffic
# You could modify this to only allow certain traffic -A OUTPUT -j ACCEPT
# Allows HTTP and HTTPS connections from anywhere (the normal ports for websites)
-A INPUT -p tcp --dport 80 -j ACCEPT
-A INPUT -p tcp --dport 443 -j ACCEPT
# Allows SSH connections
# The --dport number is the same as in /etc/ssh/sshd_config
-A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT
# Now you should read up on iptables rules and consider whether ssh access
# for everyone is really desired. Most likely you will only allow access from certain IPs.
# Allow ping
# note that blocking other types of icmp packets is considered a bad idea by some
# remove -m icmp --icmp-type 8 from this line to allow all kinds of icmp:
#
https://security.stackexchange.com/questions/22711
-A INPUT -p icmp -m icmp --icmp-type 8 -j ACCEPT
# log iptables denied calls (access via 'dmesg' command)
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7
# Reject all other inbound - default deny unless explicitly allowed policy:
-A INPUT -j REJECT
-A FORWARD -j REJECT COMMIT
5、After configuring file，that you can type following commands to use these rules：
（iptables provides function which saves current running rule）
#iptables-save > /etc/iptables.up.rules
#iptables-restore < /etc/iptables.test.rules
Configure the Firewalls with NanoPi M3
