2. Before installation

The ISP-Go server can be installed on Debian Jessie/Stretch/Buster, choose the amd64 packet. 32bit computers are not supported, arm64, i386, and other packets are not supported.

Please make sure that the standard repositories are added to the /etc/apt/sources.list, as this will be required for installing additional ISP Go components (nginx, redis, etc.).

After you installed the Debian amd64 OS please run the following commands. All commands must be executed by the root user.

• Install SSH and iptables if they are not installed yet

apt-get install ssh iptables

• Using iptables, block access to port 53 (both UDP and TCP) from networks that do not belong to the provider. A minimal example for an ISP with a 192.168.5.0/24 network:

iptables -A INPUT -p udp --dport 53 ! --src 192.168.5.0/24 -j DROP 
iptables -A INPUT -p tcp --dport 53 ! --src 192.168.5.0/24 -j DROP

It is impossible to automate this step, because the provider may have some ready-made script for configuring the firewall, and it is a bad idea to add rules blindly on top of it.

• You need to make iptables rules automatically apply after a server reboot. One way to achieve this is to install the package iptables-persistent:

apt-get install iptables-persistent

• Save the rules:

service netfilter-persistent save