Connection between GNS3 VM and another VM running Tacacs+ on VirtualBox

Scenario:

• Host machine running Ubuntu and VirtualBox
• VM#1 guest Lubuntu and GNS3 v1.3.7
• VM#2 guest Ubuntu server and tacacs+

In order to make VM#1 and VM#2 communicate do the following:

1. Create a new Host-only network by editing VirtualBox preferences
2. Add a new network adapter on each VM using the Host-only network adapter and select the previously created Host-only network
3. Change the Promiscuous mode setting to "Allow all" in both VMs
4. Run GNS3 as an Administrator 
5. In  GNS3 add a new cloud element and configure it using the ethernet interface pointing to the Host-only adapter
6. Connect the cloud element to router in GNS3
7. Configure static IP addresses or use a DHCP server (select respective option in VirtualBox)
8. "No shut" the respective ports on all devices involved
9. You should be able to ping from the router toward the tacacs server and the opposite

Notes

1. Always run GNS3 as Administrator. Otherwise nothing will work.
2. Don't forget to enable Promiscuous mode. Without it I could receive IPs from the DHCP server, but ping wasn't working.
3. You can avoid using the Host-only network and use your normal lan interface where your ADSL router is connected. That way your GNS3 VM will be able to connect to the internet.