No Internet access on Windows Phone 8 emulator (despite working connection in Windows 8)

The Windows Phone 8 emulator runs in it's own (Hyper-V) VM with it's own networking and MAC addresses.

Using the Hyper-V Manager --> Actions --> Virtual Switch Manager, check the setup of the virtual switch; I believe that by default it's set to "Internal network" which mean no outside access.

"An internal virtual network is not bound to a physical network adapter. As a result, an internal virtual network is isolated from all external network traffic."

Since you say you have no router and just plug the host directly into the ISP's network to get Internet, you'll need to figure out a way to share the network connection. Either by changing the virtual switch setup to bind to an actual (extra) physical adapter in the host, which is then hooked into a router or alike (to split the network connection from the ISP), or by keeping it as "Internal Network" and then enabling Internet Connection Sharing on the host (so it acts as a router).

More info on setting up Hyper-V's networking from MS here: Configuring Virtual Networks

WP8 emulator troubleshooting covers it as well: Troubleshooting the Windows Phone 8 Emulator

Here's some instruction on how to setup ICS for Hyper-V VMs on Windows 8: Share Internet Connection with Hyper-V Guests (NAT) on Windows 8