OK, I just did a limited port scan for basic common TCP ports to the IP address you posted as being used by your router R1, and I did not get a ping reply, or responses on ports 80 or 443. In fact, i can get no ping or traceroute to the entire 188.8.131.52/29 subnet, and a whois query returns "IANA-RESERVED".
EDIT: Oops, I just noticed that you said that you modified your IP information before posting.
Do you have your SMC firewall settings like the image below?
While the SMC firewall for the static IP addresses does work (I have used it myself in the past), it might be best to temporarily disable it for testing.
Just for grins, you might want to browse from your S1 server to my »portscan.dcsenterprises.net
and do the port scan test to see if you get a response on ports 80 and 443. (and to also see if my server sees the correct IP address for your R1/S1.--
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