Linux – Why doesn’t the linux hyper-v guest display its ipaddress in hyper-v manager

If the VMs can't ping even between themselves, then something is definitely broken here, and it's not related to the RRAS service running on the host; regardless of their default gateway's behaviour, machines placed on the same network and with proper IP configuration should be able to talk at least between themselves.

Did you try disabling Windows Firewall on the guests?

Also, as per Greg Askew's suggestion, I'd try removing RRAS on the host; maybe it's messing up something with Hyper-V networking.

Microsoft, like any company, responds to pressure from customers. Unfortunately, for a while there they were in a big fight with Red Hat during which they weren't even responding to customer demands for Red Hat support but that has been resolved. Microsoft claims that SUSE and Red Hat are the primary distros that people are asking for and indeed the two of them make up a huge chunk of the distros in large companies (the ones that most easily get Microsoft's attention). Given how long it took and how painful it was to get Microsoft to support these two, I wouldn't hold my breathe waiting for another distro.

Technically, the issue is performance. You can build a VM on Hyper-V and run any distro you want and it will work if you use the legacy NIC and normal IDE storage controller. The problem you'll find is that the performance of the VM with the legacy NIC and the IDE controller without better drivers is poor. With the release of Hyper-V R2 (and Windows 2008 R2), Microsoft released the Linux Integration Components Version 2. Once installed, you can use the synthetic NIC which is much better and you'll find that the IDE controller performs on par with a Windows VM. Microsoft's testing and documentation for the integration components was done only with SUSE and Red Hat but many people have been able to get them succesfully installed in other linux distros and they are working fine. You just can't call Microsoft for help if something breaks or acts strange. The Integration Components were also released under GPL so other distros might themselves choose to integrate them to make things even easier.

The Integration Components are here: http://www.microsoft.com/downloads/details.aspx?FamilyID=c299d675-bb9f-41cf-b5eb-74d0595ccc5c&displaylang=en

Here's a howto for Ubuntu: http://blog.allanglesit.com/Blog/tabid/66/EntryId/22/Hyper-V-Guests-Linux-Integration-Components-Ubuntu-and-Debian.aspx