GNS3 - VitualBox Part 1: Creating an Internet Gateway and Private Network

Configuring a basic GNS3-VirualBox system (one Linux Gateway router, two Cisco 7206 routers connected over OC-3 and a Windows Domain Controller).  The Linux gateway provides a simple connection to the host operating system (Ubuntu 14.04) using Quagga routing software; it also communicates with Cisco routers, providing the host operating system full visibility of the virtual Cisco network.

Introduction

The illustration above depicts what will be configured:  a shared wireless adapter for the host operating system (Ubuntu 14.04) and Debian Linux Gateway (in a virtual data center Coudersport).  A wireless router running DD-WRT provides DHCP addresses to the shared wireless adapter.  The virtual Cisco network consists of two 7206 routers.  One router is in the Coudersport data center and the other is in the Philadelphia data center.  There is a Windows 2012 R2 server in the Philadelphia data center; Fast Ethernet adapters are connected to GNS3 virtual Layer 2 switches.  Ultimately, the test of the network's configuration is the Windows server connecting to the Internet.

Adding the Debian Linux Gateway

The Debian Linux Gateway requires two Ethernet adapters:  one is bridged (through VirtualBox) to the host laptop's wireless adapter.  The second is a linked to the GNS3 software using a "Generic Driver."

The host laptop and Debian Gateway use Quagga to communicate with other routers -- and themselves.  Wireless routers frequently provide addresses in the 192.168.0.0 - 192.168.254.0 range; the host laptop and Debian Gateway are configured to communicate over these DHCP addresses using the command:

network 192.168.1.0/24 area 192.168.0.0

as the router most frequently used assigns an address in the 192.168.1.0/24 range.

The host laptop is assigned the router-id 192.168.1.1 and the Debian Gateway VirtualBox server the router-id 192.168.1.2.

The Debian Gateway is also the starting point of the Backbone OSPF area 0.0.0.0 with the command:

area 0.0.0.0 range 172.16.0.0/12

The equivalent Cisco IOS command is:

area 0.0.0.0 range 172.16.0.0 255.240.0.0

This defines the private network range 172.16.0.0 - 172.16.25.255 as belonging to the Backbone Area.  Properly configured, the Debian Gateway will be adjacent to the host laptop in the 192.168.0.0 area.

Adding the Coudersport 7206 Router

The Coudersport Cisco 7206 router is connected to the Debian Gateway over Ethernet and a GNS3 virtual Layer 2 switch.  The interface FastEthernet0/0 is configured with the commands:

ip address 172.16.254.1 255.255.255.0
duplex full
no shutdown

The OSPF process is configured with the commands:

router-id 10.0.0.1
area 0.0.0.0 range 172.16.0.0 255.240.0.0
network 172.16.254.0 255.255.255.0 area 0.0.0.0

These commands set the interface IP address, the router-id, define the backbone network address range and add the local network to the backbone area.  Upon configuration, the router will be adjacent to the Debian Gateway (running Quagga) in the backbone area (0.0.0.0).

Adding the Philadelphia 7206 Router

The Philadelphia 7206 router is connected to the Coudersport 7206 router over a point-to-point OC-3 line.  In addition to the Fast Ethernet cards in slot 0, we must also add PA-POS-3 cards to slot 6 in each router chassis.


On the Coudersport router, the P6/0 interface is configured with:

ip address 172.16.0.1 255.255.255.252
no shutdown

On the Philadelphia router, the P6/0 interface is configured with:

ip address 172.16.0.2 255.255.255.252
no shutdown

This defines a point-to-point network (172.16.0.0, broadcast address 172.16.0.4).  The Philadelphia router also needs a private network to host the Windows Domain Controller (see below). The Fast Ethernet interface is configured with the commands:

ip address 10.64.0.1 255.255.255.0
duplex full
no shutdown

The Philadelphia router's OSPF process is configured with the commands: 

router-id 10.64.0.1
area 0.0.0.0 range 172.16.0.0 255.240.0.0
area 10.64.0.0 range 10.64.0.0 255.255.0.0
network 172.16.0.0 255.255.255.252 area 0.0.0.0
network 10.64.0.0 255.255.255.0 area 10.64.0.0

The Coudersport router requires adding network 172.16.0.0 255.255.255.252 to area 0.0.0.0 as well.  Upon completion, the two routers will form an adjacency in area 0.0.0.0.  The Philadelphia router's connectivity to the Internet may be tested by pinging a public IP address (e.g. 8.8.8.8).

Adding the Windows Domain Controller

Finally, add the Windows Domain Controller to the Philadelphia network.  Set the server's IP address to 10.64.0.2.  At that point, it will connect to the Internet through the virtual routers.

The video below illustrates the entire configuration process.