I have a Debian 8 machine, where I've configured two VLAN interfaces in /etc/network/interfaces. Now I've deconfigured it (deleted information from interfaces file), restarted networking, and now it does not work at all. /etc/init.d/networking restarts correctly, I see the IP addresses on interfaces from console, but I can't reach them anymore. Furthermore, I still see my VLAN interfaces in ip addr show command (and in /proc/net/vlan/config file). If I try stopping VLAN interfaces by ifdown script, it says that interface is not configured. All 4 interfaces are configured as DHCP with allow-hotplug. Routing is correct.
Seems that the problem is somewhere in VLANs, because if I try pinging default gateway, destination host unreachable answer comes back from VLAN IP, and if I ping it via eth0, all works correct. Where did it become stuck?
Try and see if your vlan interfaces are still removable via vconfig:
Also, sometimes when "ifdown" gives that error using ifconfig still works:
One option to try: