A client is attempting to use multiple SSIDs on access points connected to our Cisco switches.

The switches are configured with 802.1Q trunks tagging the required VLANs (in this case 110 and 116).

The TP-LInk access point is configured with two SSIDs , one assigned to each VLAN (110 and 116)

Both SSIDs can be connected to successfully by clients, however clients on the second SSID (116) do not get an IP address from DHCP. Setting a static IP works fine which along with other indicators seems to confirm that the VLAN trunking between the switch and the access point is working ok.

The DHCP server is hosted on a router connected to both VLANs. It recieves dhcp discovers from clients on both SSIDs and sends back appropriate offers. When sniffing the trunk port on the switch that the access point is connected to we see that the dhcp offers are making it this far. The offers however, do not appear to be forwarded to the client by the access point.

With further research we have found that whichever of the two VLANs is set as the native VLAN on the switchport trunk works fine, the other exhibits the problem. If neither VLAN is set as native on the switch trunk, both SSIDs exhibit the problem. In short it seems the problem only occurs with tagged VLANs.

Access points from other manufacturers (Draytek and Cisco have been tested) do not seem to have this problem when connected to the same trunk port and configured with the same SSIDs and VLANs.

Could this be a firmware issue or is there some subtle configuration option we are missing?

Thanks