Comment 53 for bug 1434986

I think I am experiencing the same issue.

This is a brand new desktop PC with 16.04 LTS installed from scratch i.e. not an upgrade from a previous version.

This is wired ethernet (GbE) i.e. not WiFi.

Immediately after a boot, the user logs in and attempts to access a computer on the local network (so no possibility of internet problems and most likely no possibility of DNS problems). The attempt to use the network fails.

ifconfig appears to show everything normal - ethernet is UP and an IP address is assigned. Icon at top right of screen appears to show everything normal (up-arrow-down-arrow icon is present). (IPv4 has an IP address assigned manually but the same malfunction was occurred when, initially, it was using DHCP, I think.)

ping of a host on the local network fails.

Wait about 25 seconds though and suddenly it's working.

This is not good user interface because the user has no way of seeing when the network starts to work. It's not a good user experience either as the computer is working significantly before the network is usable.

syslog from boot doesn't show anything obviously wrong - NetworkManager sees the ethernet and appears to bring it up - but then about a minute after the first message of the boot I see that NetworkManager reports that the link is disconnected and then connected.

Don't know whether it matters but both IPv4 and IPv6 are in use. IPv6 uses DHCP. Once all the weirdness has finished, both IPv4 and IPv6 work correctly.