GNS3 Cannot Connect Network Interfaces when running on VMware vSphere

KB ID 0000671 


I have plenty of real ASA firewalls to play with, but it’s getting round to re-certification time, so for ease I thought I’d run up a Virtual ASA on my vSphere 5 box just for testing and breaking.

However no matter what type of Virtual Network adaptor I used (vmxnet3, e1000, etc) I could not connect to the virtual firewall.


1. Firstly make sure you actually have an IP address in the correct range set on the ASA, and the interface is up.

Virtual ASA GNS3 Connected

Note: To connect a virtual ASA to the outside world you need to have a ‘Cloud’, then assign your machines NIC to the cloud. Finally you join the cloud to the ASA with a switch.

2. From my laptop (out on the network), I could not connect to, or ping the ASA 🙁

Cant Ping Virtual ASA

3. However if you log into your ESX/vCenter Server and change the settings on the virtual switch that the parent VM is attached to. Configuration > Networking > Switch > Properties > vSwitch > Edit > Security Tab > Change Promiscuous Mode to Accept > OK.

vSphere Enable Promiscuous Mode

4. Now it works!

Can Ping GNS3 Device

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Author: Migrated

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