configure-linux-as-nat-rhel

configure-linux-as-nat-rhel

# This script configures a linux box as a NAT router (PAT), suitable for use
# for AWS instances in a VPC Private Subnet to communicate with the Internet
#
# To setup a NAT:
#     # Create an AWS instance in Public Subnet
#     # Disable src./dest. check (networking menu in UI)
#
# To install, login to instance:
#     sudo su -
#     curl http://gist.github.com/.../raw/... | bash -s
#

cd /root
yum -y update
yum -y update aws*

echo 1 > /proc/sys/net/ipv4/ip_forward
echo 0 > /proc/sys/net/ipv4/conf/eth0/send_redirects

/sbin/iptables -t nat -A POSTROUTING -o eth0 -s 0.0.0.0/0 -j MASQUERADE
/sbin/iptables-save > /etc/sysconfig/iptables

mkdir -p /etc/sysctl.d/

cat <<EOF > /etc/sysctl.d/nat.conf
net.ipv4.ip_forward = 1
net.ipv4.conf.eth0.send_redirects = 0
EOF