[ubuntu] A start job is ruing for raise network interfaces (5 mins 1 sec) in ubuntu16.04

i have installed ubuntu 16.04 in my laptop.
starting ubuntu is fast when i have LAN cabled coected.

when LAN cable discoected then it is taking around 5 minutes to get login screen.
it was showing this message with timer on screen at that long time.
"A start job is ruing for raise network interfaces (2 minutes of 5 mins 1 sec)"

1) how can i skip this delay (5 mins for waiting network).
like if there are some shortcut keys which i typed then the startup script should not wait for 5 mins, it should directly skip the network interface checking and go to login screen.

or
2) how can i permanently stop network interface check only when LAN cable not coected.

Thanks
Thani