Ubunt 17 at start up does not connect on lan

[SandroSys]

Good evening to all of you, first of all i hope to ask my question in the exact topic (first time, sorry).
My problem is: i start Vb with ubuntu 17 and does not connect on lan but only at start. I disable/enable (in ubuntu) the connection and it works properly ... the clients connect to the VM , ubuntu browse internet etc etc ... until i power off the server and next day the issue repeats.
Ubuntu and the host has fixed IP adress and so all devices of the lan, lan of vm bridged set.
There are two lan (CABLED not wifi):

The first (here is the server host with VM Ubuntu guest and other device)
10.71.x.0
255.255.255.0
gateway (cisco fastweb NOT ACCESIBLE) 10.x.x.x

and the second (here are the clients and printer)

192.168.x.0
255,255,255,0
2 ° gateway (technicolor TIM accessible) 192.168.x.x
In VM ubuntu i insert two ethernet cards because i've to connect with the two lan , otherwise the client can not connect with VM.

Perhaps the gateway has rpoblems?
Any idea to suggest ?

Many thanks
Sandro

[SandroSys]

Goodmorning everyone! I solved the problem (alone)!
This type of problem depends on the host drivers and consequently their virtualization in the virtual box. if drivers are generic and not proprietary, or are not up-to-date or ruined or simply are not properly developed by the manufacturer (yes, it also happens, and not infrequently), even their virtualization is not right. They work but they are not his. The process does not start (as it is excluded from other operating system processes) and the guest does not connect to the network. Restarting the process (disable / enable network functionality) works properly. then upgrade drivers forever!
I hope this solution is useful for those who read ... greetings to everyone