VPN site to site issue

hello,

i am working on connecting my two main company sites.

But i'm starting to have no idea, i would like to get some help :)

Site A with a cyberoam CR35wiNG and site B with a Sophos XG125W.

Both are behind a modem router, with port forwarding for the VPN communication.

( i am wondering if it's the problem : both has the same private address to go to the modem router (WAN port ) 192.168.10.1)

I have created my IPsec VPN by following : https://community.sophos.com/kb/en-us/123600

i am able to active them, but when i try to connect i get an error message.

(i think the configuration of the VPN are OK, cause i have tested with an IP Public directly on the router  , and the VPN works great, i could had access to my server on the other site.

unfortunately, i am not allowed to keep this configuration.)

actually, i have configured NAT only on the modem router, and nothing the Sophos and Cyberoam.

Did i missed somethig somewhere ?

this is the log i get when i try to connect :

Maybe the other problem is linked.

I have configure L2TP VPN for remote user.

I am able to connect and access to the LAN only on a private WIFI or using the IPhone as router.

When i on site A, and i want to use my remote access to access on site B (and vice versa) i always have a error :

so i guess i have an error somewhere but i have no clue where to check.

Thanks for your help and your time,

Best regards,

Thomas,