If I understood it right, your web server must access the files (use DocumentRoot of your httpd.conf) from another server (file) situated in a vlan environment. I think this can help; make it sure that the web server can connect to the file server. Second, you must be able to mount a remote filesystem on the file server. There are plenty of ways, but the easiest and fastest would be the NFS (Network File System).
Just Do It!