Description of problem:
I tried and configured vlan interface with sat6.1 beta snap6 compose2. vlan interface configured successfully when i defined the vlan id for selected subnet.

Let's say user forgot to set the vlan id on a selected subnet and configured the vlan interface while creating new host. The new host form was submitted successfully and when host is provisioned successfully, user got to know that interface was not configured. So UI should raise an error/warning on new host form submit, if no vlan id is set on selected subnet. 

Version-Release number of selected component (if applicable):
sat6.1 beta snap6 compose2 (Satellite-6.1.0-RHEL-6-20150311.1).

How reproducible:
always

Steps to Reproduce:
1.
2.
3.

Actual results:
user forgot to set the vlan id on a selected subnet and configured the vlan interface while creating new host. The new host form was submitted successfully and when host is provisioned successfully, user got to know that interface was not configured.

Expected results:
 So UI should raise an error/warning on new host form submit, if no vlan id is set on selected subnet. 

Additional info:

here is the out of config file when when vlan id is not set on selected subnet.

# eth0.1 interface
real=`ip -o link | grep 52:54:00:81:0d:2c | awk '{print $2;}' | sed s/:$//`
  real=`echo eth0.1 | sed s/eth0/$real/`

cat << EOF > /etc/sysconfig/network-scripts/ifcfg-$real
BOOTPROTO="none"
IPADDR="192.168.100.121"
NETMASK="255.255.255.248"
DEVICE="$real"
ONBOOT=yes
PEERDNS=no
PEERROUTES=no
EOF

please note that in this case VLAN=yes is missing. This will be only set when valn id is set on selected subnet.