I do not have your model but, for those that I have, I would expect the following to apply: Your AP connects users to the VLAN. It does not provide clients with IP and/or gateway addresses - that is the job of your DHCP server which should be present on each VLAN unless you use fixed IPs. Clients should not need gateways to reach the DHCP server. In other words, you have to configure the DHCP server on each VLAN to give clients the gateway address for that particular each VLAN. The gateway configured under AP management is used by the AP so that you can connect to and manage it. It is not used by clients. I hope this explains why there is only one gateway address and where you may need to configure the required gateways instead.