Orbi Setup different gateway on each LAN

Hi,

I am setting up my Orbi6 SXR80 wiah an additon gateway/router on which I have a VPN client running.

I would like to setup this second gateway on my VLAN20.

all my devices connect to LAN1 (and Wireless1) will directly connect to internet

All my devices connected to LAN2 (and Wireless2) on VLAN20 will connect to internet through my VPN client.

The setup is as below.

SXR80

   |---- port1 ---- internet modem

   |

   |---- port2 (VLAN1) ---- 192.168.1.4 /Gateway router2

   |                                                              | port2

   |---- port2 (VLAN20) ----192.168.20.2---|

currently, my router2 is the DHCP server for the devices connected to VLAN20.

I would like to have my SXR80 to be DHCP server on LAN2. But in this case, how do I define my router2 as Gateway ?

Shall I create a static route to route all traffic on VLAN2 to router2 ?

Thanks for your help