The default installation of, for example, a Linux Virtual Machine (VM) in Parallels on, say, a Mac uses a shared network mode that prevents incoming log in attempts (ssh). There is a simple fix.
Recently, I ran across an interesting situation with Parallels. As you know, I'm a regular user and reviewer of the Parallels Desktop. For example, "Parallels Desktop 9 for Mac: Faster, Better Windows Experience." So when my wife told me that she couldn't log in (ssh) from her Windows 7 PC to her copy of Fedora 19, a Virtual Machine running inside Parallels Desktop 9 on her iMac, I was intrigued.
Her problem arose from the fact that the default installation of a VM uses a Shared Internet connection. The VM and the host ride along on the same DHCP address issued by a local router. This setting is in Parallels > Configuration (for a specific VM) > Hardware > Network 1.
From the Parallels forum: "If you've chosen the (default) shared network option, the Parallels [Network Address Translation] NAT service acts as the DHCP server to the VM. The address [space] is 10.211.55.1 to 10.211.55.254.... As a result, the VM doesn't appear in your network and you can't see behind the NAT 'firewall'."
The ifconfig command verified that hidden address is in Shared mode with an address of 10.211.55.20.
As a result, if you try to, say, log in via ssh from a different computer on your LAN to that VM, it won't work. The VM will be invisible, and that might be a good thing if you want it — or not if you don't. (Of course, nothing keeps the VM from going outbound to the Internet, say, with a browser.)
The way to fix this is to go to the configuration for your VM when it's halted. Configure with Configuration > Hardware > Network 1. Then select "Bridged to Default Adapter." Then reboot your VM.
When you do that, Parallels acts as a simple IP bridge. The Fedora VM, in this case, now gets its IP address directly from the LAN's local router, naked so to speak. The way to confirm this, again, isto open a terminal window and enter the ifconfig command.
In this case, my host iMac had an IP address of 10.1.10.27 and the Fedora VM's was 10.1.10.30. That made both equally visible to all the other computers on my LAN, behind the router.
Here's what the login session looked like from yet another Mac (10.1.10.29) on my network. Voila!
This configuration change is subtle but has significant consequences for the visibility of your VM on the LAN. I enjoyed exploring it, and I hope it comes in handy for Parallels Desktop users.