i86bi-linux-l2-adventerprisek9-15.1a.bin on Cisco IOU via GNS3

I set up the following topology in GNS3: enter image description here

All I did was power on the devices, connect them and do a 'no shut'-command on their connected interfaces.

I thought spanning tree was enabled by default but when I do a show spanning-tree on any of the switches it says "No spanning tree instances exist".

The FastEthernet1/0 ports of ESW2 and ESW3 both show a status of UP/Down.

Do I have to enable the port as trunks before spanning-tree gets enabled? Why is the fa1/0 of those two switches UP/Down? It looks almost like it might be blocking?

  • What is the status on the interfaces on ESW1? run the command "show VLAN" and post the response.
    – Ron Trunk
    Sep 14, 2015 at 12:51
  • If someone has provided an answer that resolves your question, please consider marking it as the accepted answer. This will reward both the person who provided the answer and yourself with additional reputation. If you do not do so, your question will periodically get refreshed back to the main page, possibly distracting community members from other questions they may be able to help answer for other users. Thank you.
    – YLearn
    Sep 14, 2015 at 20:43

1 Answer 1


I looked again and found I was using the wrong ports.

The switches were configured with a GT96100-FE (2 ports) and a NM-16ESW module.

I was using the GT9600 ports (fa0/0 -fa0/1) which don't even support switchport mode commands.

I plugged everything into the NM module and it worked as expected. Sorry my bad!

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.