I am unable to get  a  "virtual external network" on a Hyper-v on a Windows 2008 Server Core SP2  operating system with 2 NICs to work without packet loss. . I am hosted by and strongly suspect that my Hoster/Provider does not accept "virtual" MAC addresses like those used by Hyper V 00-15-5d..nn nn mm.

Basically, I hae set up a system with 2 child VMs (Virtual machines with WK 2008 server) in a parent system.

Setting up a external virtual network, under Hyper-v, I have good quality links (as shown by ping) between the child VMs and child to parent.

Communication to IPs on Internet and to the router works from the parent but with suffers 10% loss . Also TTL to internet IPs experience a surprising decrease in TTL value, 59 instead on a expected 122,.

If I give a valid Mac (one from my Hoster/Provider) to child VM, I can connect to Internet but experience the same loss of packets.

When set up of the external Virtual Netwok, in the Microsoft-Windows-Hyper-V-Network-Admin log I noticed the message::

Event[3]:
  Log Name: Microsoft-Windows-Hyper-V-Network-Admin
  Source: Microsoft-Windows-Hyper-V-Network
  Date: 2009-09-21T23:28:27.602
  Event ID: 14106
  Task: N/A
  Level: Information
  Opcode: Info
  Keyword: N/A
  User: S-1-5-18
  User Name: NT AUTHORITY\SYSTEM
  Computer: SD-16090
  Description:
Static MAC address '00 15 17 27 9F A8' for 'Intel(R) PRO/1000 MT Network Connect
ion - Virtual Network' (Intel(R) PRO/1000 MT Network Connection - Virtual Networ
k) conflicts with another adapter.

I have the impression that packets are "looping" in the virtual switch and finally finds the way out.?
I have just had the same problem when using   "Windows Server 2008 Standard Full En-US (64BITS)" SP2 on the same server.

Avenues explored but proved not to be the solution.:
  -I have the correct integration services
 -bridging is not acceptable to my hoster/provider
-  I have just had the same problem when using   "Windows Server 2008 Standard Full En-US (64BITS)" SP2 on the same server.
 -Dedicated virtual networks have the same problem
- internal networks are ok