Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Works great for VoIP but VPN is extremely slow

I bought this router to replace a desktop that I use as an internet router (cable internet) and to use to to put a Cisco VoIP gateway behind the router. For VoIP and general internet use, it works great but if you use VPN (L2TP in my case), the speed is excrutiatingly slow through this router. This is consistent with other users' experiences. When I put my desktop (which is an old and slow machine) back as the router, VPN speed is at least 20 times faster. This is after all my troubleshooting and I'm a networks engineer. If you need VPN, don't get this router.