Connecting 2 routers to ER605

Connecting 2 routers to ER605

Connecting 2 routers to ER605
Connecting 2 routers to ER605
2023-05-03 11:23:58
Model: ER605 (TL-R605)  
Hardware Version: V2
Firmware Version: 2.1.2



I have a peculiar solution that I need resolved. I have 2 routers configured with two different ISPs - Airtel & ACT. 

Airtel ISP comes with PPPoE through the SEROCOMM router and ACT ISP comes with PPPoE through a TPLINK Deco M5 router. ACT is my primary ISP and Airtel is secondary ISP.


I bought the ER605 as I wanted link-backup. I'm not really interested in load balancing since the speed difference between both is massive - ACT (300mbps) vs Airtel (50mbps).


Now, I wanted to know if there's a way to leave both on router mode (as opposed to bridge/access point mode). The reason is the Deco comes with Antivirus feature and is easily configurable on the Deco app - turning this to access point mode disables most of the  settings.


from what I understand, I need to setup the WAN connections directly on the ER605 but I am trying to avoid that.


If this situation is possible, I am not sure how to configure the DHCP on either the router or ER605 as I would like to avoid double NAT. There is a DHCP Relay feature on the latest ER605 firmware but I am yet to figure out how it works.


I am a novice at networking so additional explaination would be appreciated.