Perhaps I'm not comprehending your question..
But a router doesn't filter LAN activity.. all client systems can communicate with each other unconditionally.
Are you saying they cannot contact this host via private addresses (rfc1918) or your ISP assigned public IP address?
- If the former, tell the host to configure the server properly.. either the host is running a firewall of it's own (like pf), or the actual daemon is disallowing connections.
- Or the latter.. forward port 80 using the "Virtual Server" feature of that router.
I must ask though; why did you decide to use an embedded device like that.. when BSD can do the job quite nicely?
Good luck..