How do the Hyper-V machines get identical IPs even the physical machine has only 1 Network interface

hyper-vnetworkingvirtual-machines

In windows 2008 we can have multiple Hyper-V instances on the same physical machine. Generally that machine has only 1 network interface. (I assume 1 card with 1 MAC Address). Then how do the Hyper-V machines get identical IP Addresses? Does the Network adapter need to support any special features?

Best Answer

If your virtual machines are getting the same IP, it is probably an RFC1918 private address, which is being NAT'ed by the Hyper-V software hosting the guest OSs.

If your virtual machines have independent IPs on the same VLAN as the host, then Hyper-V is probably using a bridging virtual network adapter. This virtual adapter programs the network card to respond to several IP's at Layer 2 and forwards the correct packets to the guest OSs.

Related Solutions

Virtual Machines – Safe Range of MAC Addresses for Virtual Machines

There are actually 4 sets of Locally Administered Address Ranges that can be used on your network without fear of conflict, assuming no one else has assigned these on your network:

x2-xx-xx-xx-xx-xx
x6-xx-xx-xx-xx-xx
xA-xx-xx-xx-xx-xx
xE-xx-xx-xx-xx-xx

Replacing x with any hex value.

How to create a Hyper-V Internal network

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.

Best Answer

Related Solutions

Virtual Machines – Safe Range of MAC Addresses for Virtual Machines

How to create a Hyper-V Internal network

Related Topic