I have a mixed environment; Windows and Linux. Linux is made up of a number of distros and flavours; Vanilla Ubuntu server, ElementaryOS, Vanilla Arch and some network devices that run BusyBox (Ubiquity).
On my ElementaryOS PC, I am wirelessly connected. When I try to contact a local Ubuntu server, I am given my external IP address (both of these servers have an externally available FQDN DNS entry with the same name).
But, if I disconnect from the network and then reconnect, I have about 10 seconds where I can ping the local name and am presented with the INTERNAL IP address. After this ten seconds or so, any further pings return the external IP address.
This does not happen from any of the other Linux boxes... so, I have to assume that it is something to do with the services on this ElementaryOS PC.
I have added DNS entries to systemd/resolved.conf as advised elsewhere. I have added a defined entry for DNS in NetworkManager (which I do no want to do... I want to use the DHCP settings) amongst other things...
I am not looking for a work around, am looking for a fix. I am happy to change network managers if that can solve things.
The thing I don't get is what is the process that is changing the results- it works correctly for ten seconds then goes haywire...
Any thoughts gratefully received.