I apologize for the delay in posting the next tutorial in the virtual voice lab but I ran into a problem communicating from the HQ router to the host Ubuntu server. I thought I was able to communicate from the HQ router to the host during the Headquarters build tutorial….but I was wrong.

 



 

I discovered that I was able to communicate with every device on the LAN except the actual host machine. While troubleshooting, I finally read the GNS3 FAQ. Then I learned how to solve the problem with Josh Atterbury’s posts: ‘Dynamips External Cloud Interface on Linux – Part1 and Part2.

I have altered Josh’s setup a bit but the theory is the same. If you are running Ubuntu, you just need to install ‘uml-utilities’ and ‘bridge-utils’. Once the tap interface has been activated, you will need to change the GNS3 cloud object to use the tap0 interface instead of generic NIO and eth0.

 

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Here are the steps to manually create a bridge group.
======================================

  1. Create a tap interface
    sudo tunctl -t tap0
  2. Remove ip addressing and set eth0 and tap0 to promiscuous mode
    sudo ifconfig tap0 0.0.0.0 promisc up
    sudo ifconfig eth0 0.0.0.0 promisc up
  3. Create a new bridge interface
    sudo brctl addbr br0
  4. Add tap0 and eth0 to the bridge group
    sudo brctl addif br0 tap0
    sudo brctl addif br0 eth0
  5. Enable the bridge interface and give it an ip address
    sudo ifconfig br0 up
    sudo ifconfig br0 10.10.10.99/24
  6. Configure the default route
    sudo route add default gw 10.10.10.254

 

 

Here are the steps to reverse the changes (these can be copied and pasted in)
======================================

sudo ifconfig br0 down

sudo brctl delif br0 eth0
sudo brctl delif br0 tap0

sudo brctl delbr br0

sudo tunctl -d tap0

sudo ifconfig eth0 up
sudo ifconfig eth0 10.10.10.99/24

sudo route add default gw 10.10.10.254

 

 

Add the following to your /etc/network/interfaces config file if you are using static addressing.
======================================
auto br0
iface br0 inet static
address 10.10.10.99
netmask 255.255.255.0
gateway 10.10.10.254
bridge-ports eth0 tap0
pre-up ifconfig eth0 0.0.0.0 promisc up
pre-up ifconfig tap0 0.0.0.0 promisc up

 

 

Add the following to your /etc/network/interfaces config file if you are using dhcp.
======================================

auto br0
iface br0 inet dhcp
bridge-ports eth0 tap0
pre-up ifconfig eth0 0.0.0.0 promisc up
pre-up ifconfig tap0 0.0.0.0 promisc up

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