Is this the designed behaviour for NetworkManager

[Tim Coote <tim+gnome org coote org>]

Hullo

I’m starting to migrate my fedora stock to NetworkManager. In one particular test scenario, I tried to create 
a direct copy of the final machine configuration using NM and the old "systemctl start network” approach. The 
VMs are temporally separated (ie I spin up the old one save interrogation results about configuration; kill 
it and repeat with the new one).  The only differences between the two machines should be the hostnames (so 
that the puppet configuration knows them as different machines) and the mac addresses.

One inconsistency that I’ve found is that the NetworkManager cannot seem to spin up a tunnel unless the ipv4 
addresses differ between the VMs. For the NM controlled VM, pulling apart the actual command run, I see:
[code]
nmcli con up uuid 4a341ad1-3e31-7ee8-82ee-2019bf995ad8
<response>
Error: Connection activation failed: No suitable device found for this connection.
[/code]

where the uuid represents the sit1 device. However, on the same VM (either directly invoked or by turning off 
NM and running ifup sit1):
[code]
/etc/sysconfig/network-scripts/ifup-sit sit1
[/code]

spins up the tunnel.

If I put the ‘copy’ VM on different IP address(es). NM seems happy to spin up the tunnel. Note that in both 
cases there are no conflicting computers/ip addresses on the network at the same time.

Am I (probabably) seeing the intended behaviour for NM - in which case I need to modify my testing approach - 
or do I need to dig further to confirm a bug?

tia

Tim