Guys,
I was facing a Linux BUG that was fixed only in 3.18.
Here it is:
So, with Linux 3.16, it will not be possible to use Jessie to create a "VLAN tagged Virtual Network" within a KVM hypervisor itself.
It will not route VLAN tagged packets.
I manually backported Linux 3.18 from Ubuntu Vivid, into Trusty:
Then, the problem solved!
I tested the Linux versions from 3.13, to 3.16, all have the same problem... Linux 3.18 is okay.
I must say that I did not tested Jessie this days but, I know that Linux 3.16 doesn't work.
Basically, Jessie can not be used in a production environment on a Corporate Network, for example... All my firewalls, VPN servers, proxies are KVM Virtual Machines. The VLAN tagged packets does not get routed, it started to work only when with Linux 3.18.
Please, pay attention into this problem before Debian Jessie release!
Best!
Thiago