manage-iptables.sh

A script which flushes all rules from Iptables and applies a new custom setup with basic examples in the script.

####Note: This script by default allows SSH on port 22 in and ICMP (ping) in to any interface for safety.

Examples:

• DNAT
• SNAT
• Blocking/Dropping
• Port forwarding
• Inbound ports (such as port 22)
• Outbound NAT (Masquerade)
• TCP/UDP/ICMP rules
• Established & Related connection tracking

Use this script to setup initial Linux Iptables routers/firewalls that either pass traffic to an internal network or initially configure a server/host firewall.

Ubuntu users

Ubuntu users will need to add the iptables-load & iptables-save scripts to /etc/network/if-pre-up.d/ & /etc/network/if-post-down.d/ respectively.

sudo cp iptables-load /etc/network/if-pre-up.d/

sudo cp iptables-save /etc/network/if-post-down.d/

Linux routing requirements

/proc/sys/net/ipv4/ip_forward must be set to 1

Linux will not forward packets through its interfaces unless this option is set to 1. Be sure to make it persistent.

Check if its enabled

cat /proc/sys/net/ipv4/ip_forward

or

sysctl net.ipv4.ip_forward

Enable without a reboot

echo 1 > /proc/sys/net/ipv4/ip_forward

or

sysctl -w net.ipv4.ip_forward=1

Persistently enable

Edit /etc/sysctl.conf and set;

net.ipv4.ip_forward = 1