Hi
It's difficult to answer your question without knowing your config.
You must have a default route for being able to access internet and build a L2L VPN. You can also have a specific static route for you L2L VPN and tunnel everything from site A to B which means A could access internet through B ISP.
But again, I'm just assuming something I don't know. If you share your config we'll be able to answer with facts.
Thanks
Francesco
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