@Jcckmc 

Unfortunately IPsec VPN cannot meet your requirements. Because it's based on local subnet and remote subnet. Only the data whose destination is remote subnet will be forwarded to VPN tunnel.

You need to use L2TP VPN, and set up dialup way as L2TP to connect L2TP VPN. Then the router will become L2TP VPN client. But unfortunately this way doesn't support encryption on TP-Link router. Cannot make sure the security.

@Andone thank you for the reply!  I was suspecting this was the case.

@Andone Wow! I wish the TP-Link support guys were this smart enough to answer my question. Wasted almost a week time trying to see how I can route all the traffic from site-b to site-a over

Andone wrote

@Jcckmc 

 

Unfortunately IPsec VPN cannot meet your requirements. Because it's based on local subnet and remote subnet. Only the data whose destination is remote subnet will be forwarded to VPN tunnel.

 

You need to use L2TP VPN, and set up dialup way as L2TP to connect L2TP VPN. Then the router will become L2TP VPN client. But unfortunately this way doesn't support encryption on TP-Link router. Cannot make sure the security.

IPSec VPN to access internet from the site-a ISP. I wish I knew this before that this is not possible in IPSec. Thanks for your help