Hello, I'm having the same problem

I'm doing PCC load balance with a cablemodem and a wimax connection. In wimax I have static IP, but in cablemodem I have dynamic IP, so the gateway may change.

I wonder if it is possible creating a small router in the same port with VLAN, for example.

ether3= 190.192.0.100 (public IP given by DHCP)
vlan-ether3= 192.168.1.254 (static IP)

Nat > Masquerade > Out Interface=ether3
Default Gateway= 192.168.11.254

I can set the IP on VLAN, but how should I do the Masquerade?

Does anyone understand my problem? I need VLAN to be the gateway for my lan and look for Internet access on ether3(which is the same port where the wire is plugged)

It's my first time with VLANs, I hope anyone can help me, thank you.