@AnnusKhan 

SFP+ WAN1 is WAN by default and can not be changed to LAN port.

which VPN are you using, can you show a screenshot of the VPN configuration?

and you should upgrade the firmware on the router, the version you are using is old.

  @MR.S 

We are using ER8411 v1.0 TP Link VPN router with OC300 Hardware Controller

I have already attempted to upgrade the VPN firmware, but I encountered the same problem. The main reason for not upgrading the VPN router is that, after the firmware upgrade, I faced another issue with dropped WAN connectivity. As a result, clients experienced internet connectivity problems. Consequently, we decided to downgrade the firmware of the VPN router, and after the downgrade, the WAN connectivity of the VPN became stable I have attached pictures of the VPN Configuration for your reference.

  @AnnusKhan 

ok, but what I don't understand is why you're having problems with SFP+ WAN1 when you haven't connected anything to this port.

I don't see any VPN screenshot, can you show me how VPN_RT is configured?

  @MR.S 

Yes, that it my question that why the VPN trying connect network from SPF/WAN1 

its already unplugged, sorry what configuration you want can you share me demo any thing 

  @AnnusKhan 

May I ask why you have 5 WAN configured? is it not enough with 1 max 2 for failover?

can you show me a screenshot of VPN_RT, isn't it a VPN tunnel to a remote site?

  @MR.S 

We have renamed our TP-Link VPN router as "VPN_RT," but we are not using it for VPN protocols. Instead, we are using it to manage and connect multiple WAN sources (5G routers) together. The WAN port of the TP-Link router is configured to use DHCP protocol, and the internet source is obtained from the five 5G routers connected to the WAN port of the VPN router.

@MR.S

If you want to remotely connect to my computer to check the configuration, I will provide you access of our hardware controller using Any Desk.

  @AnnusKhan 

ok, yes it sounds like a complicated solution, it's not that easy to help without having access to your system, you can contact support, maybe they can do a remote session to your network.
there are so many things that can go wrong when you stack 5 routers to the internet.

AnnusKhan wrote

@MR.S

If you want to remotely connect to my computer to check the configuration, I will provide you access of our hardware controller using Any Desk.

  @AnnusKhan 

No I dont do that, You have to contact support mybe they can do.

Can we disable the VPN SFP-WAN-1 port from the Remote Control Terminal?

If possible, could someone share the command?