After reviewing the post you shared, I believe that we have the correct subnet. Besides, we did not modify anything related to the cloud-init for openstack.
I didn't either. But I found it's a good test of the network! If you are using an image that doesn't rely on it you might not notice (but I would not recommend that).
After launching the instances, we are able to ping between the instances of the same subnet. However, we are not able to receive any internet connection within those instances. From the instance, we are able to ping the router IP addresses 10.42.0.56 and 10.0.0.1.
To make sure I understand:
- 10.42.0.56 is the IP of the router external to OpenStack that provides internet access
- This router is tested and working for devices outside of OpenStack
- OpenStack compute instances can ping this router
- OpenStack compute instances cannot reach the internet
If that is correct, it does not sound like an OpenStack issue necessarily, but perhaps a missing default route on your compute instances. I would check that DHCP is enabled on the internal subnet and that it's providing everything necessary for an internet connection to the instances.
Tobias