Gre Front

grefront.sh

#!/bin/bash

#
# Install iptables iproute2
# Variables
# 
#

GRE_FRONT_IP=""
GRE_BACK_IP=""

#
# DO NOT CHANGE ANYTHING PAST THIS POINT
#

# make sure iptables isn't blocking FORWARD

iptables -P FORWARD ACCEPT

# enable IP forwarding and proxy ARP so we can forward our DDOS IP

sysctl -w net.ipv4.ip_forward=1
sysctl -w net.ipv4.conf.eth0.proxy_arp=1

# bring up our GRE to our Backend server

ip tunnel add gre1 mode gre local $GRE_FRONT_IP remote $GRE_BACK_IP ttl 255
ip link set gre1 up

# add local IP addresses

ip addr add 192.168.168.1/30 dev gre1

# Setup NAT
iptables -t nat -A POSTROUTING -s 192.168.168.0/30 ! -o gre+ -j SNAT --to-source $GRE_FRONT_IP

# Setup Forwarding
iptables -t nat -A PREROUTING -d $GRE_FRONT_IP -j DNAT --to-destination 192.168.168.2
iptables -A FORWARD -d 192.168.168.2 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT


##!/bin/sh
##A-Server-Front
#apt install iptables iproute2
#lsmod | grep gre
#modprobe ip_gre
#lsmod | grep gre
#echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf
#sysctl -p
#ip tunnel add gre1 mode gre local front-ip remote backend-ip ttl 255
#ip addr add 10.0.0.1/30 dev gre1
#ip link set gre1 up
#iptables -t nat -A POSTROUTING -s 10.0.0.0/30 ! -o gre+ -j SNAT --to-source front-ip
#iptables -A FORWARD -d 10.0.0.2 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
#iptables -A FORWARD -s 10.0.0.2 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
#iptables -t nat -A PREROUTING -d front-ip -j DNAT --to-destination 10.0.0.2
#iptables -A FORWARD -d 10.0.0.2 -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT