ok,first you should add at least 2 vlan on AP420.
for example:
vlan 1 untagged , assign to SSID 1 (vlan 1 as the management vlan )
vlan 2 taggied, assign to SSID 2 ( vlan 2 for application)
then, you should config the swith port which connected with AP420.
vlan 1
untagged 25
vlan 2
tagged 25
that's all, when you use SSID two , you can connect the LAN as vlan 2 clients.
i hopt it's helpful.
ray