Nftables on My IT Journal

Linux Firewall & DMX Networking Lab

Wed, 17 Jun 2026 00:00:00 +0000

Objective

The lab focuses on troubleshooting real-world network failures by systematically isolating issues at each layer of the network stack.

Network Topology

LAN (User Network)		DMZ (Service Network)
192.168.10.0/24			192.168.20.0/24
__________________		_____________________

Client VM			Server VM
192.168.10.101			192.168.20.10
	|				|
	|				|
	________ Firewall VM ___________
		(Router + Firewall)

Issue 1: No connectivity between networks

Failure to connect to the webserver

Troubleshooting Workflow

Step 1 - Verify the service exists

From Server:

DMZ Network Lab - Firewall, Routing, and nftables

Tue, 16 Jun 2026 00:00:00 +0000

Objective

The goal of this lab is to design and implement a basic DMZ (Demilitarized Zone) network using Linux virtual machines, understand routing between network segments, and apply nftables as a stateful firewall.

Network Topology

LAN (User Network)		DMZ (Service Network)
192.168.10.0/24			192.168.20.0/24
__________________		_____________________

Client VM			Server VM
192.168.10.101			192.168.20.10
	|				|
	|				|
	________ Firewall VM ___________
		(Router + Firewall)

VM & Routing Configuration

Client VM

sudo netplan try
sudo netplan apply

Firewall VM (Core Router)

Linux nftables Firewall Fundamentals Lab

Mon, 15 Jun 2026 00:00:00 +0000

Objective

Lab Environment

Client VM 1 - 192.168.10.101 Client VM 2 - 192.168.10.102 Server VM - 192.168.10.10

Server Setup

Step 1 - Run web server

python3 -m http.server 8080
ss -tln | grep :8080

Step 2 - Base firewall configuration

sudo nft add table inet filter
sudo nft add chain inet filter input \
'{ type filter hook input priority 0; policy drop; }'
sudo nft add rule inet filter input iif lo accept
sudo nft add rule inet filter input ct state established,related accept