I need to use a VPN which was suffering packet fragmentation due to the overhead involved (actually I use a VPN to connect to a network which then has another VPN connection to a third network).

To determine the largest MTU size which didn’t lead to fragmentation I just ran variations on

I had a centos VM that I hadn’t used in a while, I think I cloned it from another version.

When I came to use it again I had no network andtrying to start the network I got the error message in the title.

There seem to be a few issues