Using VPCS in Gns3 to replicate host devices in the network topology

The latest version on Gns3 comes with the Virtual PC Simulator that can be used to simulate end host in the network topology in Gns3 and to do simple reachability tests like ping and traceroute. Thought there are other alternatives available as well like, Qemu and Virtual box guest however these are cpu intensive. VPCS is integrated with windows and linux machine and are very light on CPU

The latest version of the GNS3 can be downloaded from here:

http://www.gns3.net/download/

In this post we'll see how we can configured and use VPCS in our small network topology we'll be using. We'll be using as simple L2 (Ethernet Switch) and connecting two PCs in the same vlan and we'll do a simple ping test from one PC to the other.

Lets start building up the topology:

If you don't like Cloud representing the PC you can change the symbol by right clicking on the Cloud.

Let me change the symbols in my topology.

Lets see what configuration is needed to use VPCS. Right click the PC-1 and click on configured. In the node configurator click on the C node and goto NOI UDP.

Use local port as 30000 and remote port as 20000 > click on Add and Apply. Similarly configure the other PC-2 accordingly with local port as 30001 and remote port as 20001.

Once both the PCs are configured, connect them to the Switch using the NOI UDP ports.

In this situation, both the switchport 1 and 2 are configured in the Vlan 1. Lets start the VPCS configure and assign ip address to the two PCs accordingly.

I would be assigning both the devices ip address in the same subnet (192.168.10.0/24).

Lets start up the VPCS. Goto Tools on the Gns3 window and click on VPCS.

This should automatically bring up the windows command prompt, with the VPCS prompt.

Following are the options available:

The VPCS prompt is the terminal for the PCs. You can type 1 to get to the VPCS 1 or 2 to get to the VPCS 2.

Lets assign ip address to both the virtual PCs. Following is the ip address assignment format for the VPCS:

VPCS[1]> ip ?

ip [arguments]
  Configure the current VPC's IP settings
  arguments:
    <address> [/<mask>] [<gateway>]
    <address> [<gateway>] [/<mask>]
                   Set the VPC's ip, default gateway ip and network mask
                   Default IPv4 mask is /24, IPv6 is /64. In the ether mode,
                   the ip of the tapx is the maximum host ID of the subnet.
                   ip 10.1.1.70 /26 10.1.1.65 set the VPC's ip to 10.1.1.70,
                   the gateway to 10.1.1.65, the netmask to 255.255.255.192,
                   the tapx ip to 10.1.1.126 in the ether mode.
                   </mask> may be written as /26, 26 or 255.255.255.192
    auto           Attempt to obtain IPv6 address, mask and gateway using SLAAC
    dhcp -[d|r|x]  Attempt to obtain IPv4 address, mask, gateway, DNS via DHCP
          -d         Show DHCP packet decode
          -r         Renew DHCP lease
          -x         Release DHCP lease
    dns <ip>       Set DNS server <ip>, delete if <ip> is '0'
    domain <name>  set local domain name
    mtu <value>    Set IPv4 MTU to <value>, at least 576.

Assigning ip address to the second PC.

Now lets test a Ping from one PC to the other.

As you can see we can use this tool for simple reachability/connectivity test.


Using windows loopback adapter for the connectivity test:
=============================================

We can also use the windows loopback adapter for the similar purpose. Please find my other post on how to create a loopback adapter on windows machine:

http://lets-start-to-learn.blogspot.in/2014/10/creating-loopback-adapter-on-windows.html

You can create multiple loopback adapters on the windows machine and use it likewise. In the below snapshot you would see that I have created two loopback adapters Local Area Connection 3 and 5.

You can use the NOI Ethernet Tab on the Cloud to map the loopback adapter to the PCs. In our setup I have used the loopback adapter 3 and loopback adapter 5 to the two PCs accordingly.

Make the ethernet connectivity accordingly from these PCs to the ethernet switch.

You can assign ip addresses to the loopback adapter accordingly and do a ping test.

Hope this would be helpful. :)