Volete usare nginx come frontend per transmission? Niente di più semplice:
server {
listen 80;
server_name frontend;
root /srv/www/htdocs;
location /transmission {
proxy_pass http://localhost:9091/transmission;
proxy_redirect http://localhost:9091/transmission http://frontend/transmission;
proxy_set_header X-Real-IP $remote_addr;
}
}