Total newbie issue

Sounds like you don't have the switchport configured to accept 802.1q tags.

If it's a cisco switch (e..g IOS or NX-OS), the switchport needs to be in trunk mode and have the allowed vlans including your VLAN. e.g.

interface eth4/18
  description my bigip
  switchport
  switchport mode trunk
  switchport trunk native vlan 1000
  switchport trunk allowed vlan 105,108,1024-1255,2005,2015-2016
  switchport trunk allowed vlan add 2080,2088,4048-4051,4080,4086-4087

Which puts an NX-OS switchport into trunk (tagged in cisco terms) mode and allows certain VLANs. The native (untagged) vlan is set to 1000 in this case (Which we like to keep not created so that any untagged traffic is just dropped by the switch.