How to Connect GNS3 to a Physical Network | A Step by Step Guide

This article How to Connect GNS3 to a Physical Network is a no nonsense step by step guide to setting up a full hands on GNS3 lab for the serious network engineer or student. This How to Connect GNS3 to a Physical Network lab is what it says on the tin. Routing, Switching, Firewall Security, Infrastructure, Virtualisation and Internet all made possible by this advanced lab created by some of the smartest network engineers of today.

How to Connect GNS3 to a Physical Network | Connecting Switch Uplink Interfaces (Introduction)

Trust me, we understand your frustration. You really want a handson lab but GNS3 has some gotcha’s, and it’s no longer economically efficient to have a lot of kit so what do you do? Thank God, we have the answer in the steps below. It will cost you next to nothing but guaranteed to give you the full blown hands-on experience without any compromises.

You will be able to create a myriad of labs, change network topologies without much effort and extra configuration. This lab is suitable for a business, university or individuals. It’s vendor agnostic and so can support your Next-Generation ASA Firewall, Sonic Wall, Juniper, Palo Alto, HP Aruba Switch, Cisco Catalyst Switches, Windows Servers and to make it even more interesting, if it has an interface, you can lab it.

The advantage here is that you can practice full switching and routing protocols like HSRP | GLBP | VRRP, STP, OSPF, EIGRP to name but a few.

Let us put together our kit list (Some of these you may already have at your disposal)

Hardware Kit

1 x Desktop Computer or Workstation with Expansion Slots (If you own a laptop, you will need USB C to Ethernet Adapters) – Not truly reliable hence the workstation preference.
2 x 4 Port PCI-E 1Gbps Network Interface Card | 2 Access Buildings
2 x Access Switches | Cisco Catalyst Switches or HPE Aruba Switches | Vendor Agnostic

Software and Operating System

Figure 1.0 – Connect Network Device to Ethernet Adapter

Figure 1.1 – 4 Port Ethernet Adapter

Figure 1.2 – Connect Switch Uplink Interfaces

Interface 47 and 48 are our respective uplinks to Core Routers R1 and R2 respectively. To make the interface layer 3 or routed, the following configuration converts them to routed interfaces.

Example of Configuration

switch(config)# interface Fa0/47 
switch(config-if)# no switchport 
switch(config-if)#

switch(config)# interface Fa0/48
switch(config-if)# no switchport 
switch(config-if)#

Figure 1.3 – Uplinks of Switches 1 and 2

Access Switch 1

switch(config)# interface 47 
switch(config-if)# untagged vlan 1008
switch(config-if)# ip address 172.16.254.10

switch(config)# interface 48
switch(config-if)# untagged vlan 1012
switch(config-if)# ip address 172.16.254.14

Access Switch 2

switch(config)# interface 47 
switch(config-if)# untagged vlan 1016
switch(config-if)# ip address 172.16.254.18

switch(config)# interface 48
switch(config-if)# untagged vlan 1020
switch(config-if)# ip address 172.16.254.22

Figure 1.4 – Switches Uplinks at back of Desktop connected to Physical Interfaces

Step 1 – Connect Ethernet Interfaces to Desktop Network Adapters

How to Connect GNS3 to a Physical Network | Configuring Physical Network Interfaces (Part 1)

Identify Interfaces on your computer

Command: nmcli dev status

# nmcli dev status
DEVICE  TYPE      STATE         CONNECTION
eth1    ethernet  connected     eth1
eth0    ethernet  connected     eth0
eth2    ethernet  disconnected  --
lo      loopback  unmanaged     --

Command: ifconfig

eno1: flags=4099  mtu 1500
        ether 40:a8:f0:49:7b:0a  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 20  memory 0xf7c00000-f7c20000  

lo: flags=73  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 24697  bytes 24138502 (24.1 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 24697  bytes 24138502 (24.1 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Step 2 – Configure IP Addresses for Uplink Interfaces

How to Connect GNS3 to a Physical Network | Configuring IP Addresses for Network Interfaces (Part 2)

Step 3 – Connect Uplinks to Core Routers

How to Connect GNS3 to a Physical Network | Connecting Switch Uplinks to Core Routers (Part 3)

Step 4 – Test Connectivity with Pings

How to Connect GNS3 to a Physical Network | Test Connectivity with ICMP Pings (Part 4)

Download the full lab here: Connecting GNS3 to Physical Network – Multilayer Network Access Design