Slow Virtualization Networking

Posted on 1 CommentPosted in error, ip, ipv4, networking, virtualisation

I had a complaint from a customer today that there new virtual server with lots of resources was too slow on copying files and could I take a look.

So I did! The virtual server was connected to a 1GB switch via two different network cables. One was configured in the Hyper-V virtualization software as available for the guest and one for the host. In the host I could copy a test file across the network from a file server at close to the expected speed for the network:


Copying the same file from inside a virtual machine on that same host was considerably slower:


Notice the speeds. 85.3 MB/s compared to 355 KB/s!!!

I tried a tracert to the same file server. From the host I got  1    <1 ms    <1 ms    <1 ms  fileserver.domain.local[] but from the guest I got   1    <200 ms    <201 ms    <38 ms  fileserver.domain.local[]. Every host to file server tracert had a latency in excess of what I expect of some of the internet!

So how to fix…

On the host I checked which physical network card was being used by the Hyper-V guest (Virtual Switch Manager in the Hyper-V tools) and found it was Broadcom NetXtreme Gigabit Network #4 in this case. So in the host I brought up the properties of that same network card (Network and Sharing Center > Change adapter settings > and hover over each NIC to see the hardware description).


Bring up the properties of this network card and click Configure to bring up the configuration of the network card hardware for this specific NIC.

Change to the Advanced tab and select Virtual Machine Queues. Change this to Disabled.


Click OK. The network card will reset and come back online in about 3 to 5 seconds. The guest machine will be offline for this time as well. If you are changing the network card that the host uses as well, you will be disconnected from the host for this time as well (though you will be warned about this in the Hyper-V management tools).

Results when I connected to the guest again:


Now this is half the speed of the host – and I did not find on this machine other network settings to improve this, so I guess this is the impact of using virtualization over physical machines.

IPv6 Routed LAN with Windows

Posted on 2 CommentsPosted in DNS, draytek, exchange, iis, ip, ipv4, ipv6, mcm, mcsm, rras, windows

This blog is written to note down the steps needed to configure IPv6 on the whole of your LAN using Windows Server 2008 R2 as the router, but without installing RRAS.

It also uses Hurricane Electric’s IPv6 tunnel broker service to provide the IPv6 connectivity via an IPv4 tunnel as my internet provider (Virgin Media in the UK) does not provide direct IPv6 connectivity at the time of writing (Dec 2012).

Originally the plan was to do all this with the Draytek 2920 router on my network, but after days of trying I gave up as it was unable to connect to SixXS over AICCU or Freenet6/gogo via TSPC even though I had made accounts and entered the information as shown on various websites and forum. Draytek do not provide a 6in4 tunnel mode, so I needed to move to using Windows or Linux, as I have both on my LAN – though I am way more familiar with Windows!

Configuring Your Internet Router

You will need control over your internet connection as you will need to enable inbound PING responses before you can create an IPv6 tunnel. On a Draytek router this is System Maintenance > Management > untick Disable PING from the internet.

Also to allow a tunnel to traverse a NATed router, you need to allow Protocol 41 to pass the firewall. On a Draytek router this involves creating a new rule in the Default Call Filter rule set and the same under the Default Data Filter set. The settings are Direction: WAN –> LAN/RT/VPN; Source IP: Any; Destination IP: Any; Service Type: Protocol: 41; Filter: Pass Immediately.

Getting a Hurricane Electric Tunnel

Visit and create an account and request a tunnel. Once you have requested a tunnel you will get the following information on the IPv6 Tunnel tab (of which only the important information is shown, and where I have changed the values to be generic):

  • IPv6 Tunnel Endpoints
    • Server IPv4 Address: a.b.c.d (the endpoint of the tunnel at Hurricane Electric)
    • Server IPv6 Address: 2001:xxxx:wwww:65b::1/64 (this has wwww shown in bold and is the Hurricane Electric end of the tunnel they have created for you, and it will end in a 1.)
    • Client IPv4 Address: w.x.y.z (this is your external IP address of your internet connection)
    • Client IPv6 Address: 2001:xxxx:wwww:65b::2/64 (this has wwww shown in bold and is your end of the tunnel they have created for you, and it will end in a 2.)
  • Routed IPv6 Prefixes
    • Routed /64: 2001:xxxx:yyyy:65b::/64 (this has yyyy in bold and yyyy is one number higher than wwww in the IPv6 tunnel endpoints above).

On the Example Configurations tab you will get the choice of operating system to use, and you need to select Windows Vista/2008/7 from the dropdown list. This will present you with some netsh commands as shown (where the values will be your specific values rather than the generic values I show here):

netsh interface teredo set state disabled
netsh interface ipv6 add v6v4tunnel IP6Tunnel w.x.y.z a.b.c.d
netsh interface ipv6 add address IP6Tunnel 2001:xxxx:wwww:65b::2
netsh interface ipv6 add route ::/0 IP6Tunnel 2001:xxxx:wwww:65b::1

If you are behind a NATed router then you need to change the w.x.y.z value which will show your public IP address for the private IP address of the Windows Server you are going to run this set of commands on.

Run these commands from an elevated command prompt. Once complete you should be able to reach the IPv6 internet from that machine. Try ping and you should get back the IPv6 address for Facebook (showing your DNS server is IPv6 aware – Windows DNS will return AAAA, the IPv6 version of the A record, responses if your client has a valid global IPv6 address). Another destination you can attempt to ping is

You now have working IPv6 from a single server on your LAN.

Configuring The Windows Router

The next step is to enable this single server as a router. This will allow the forwarding of packets between the LAN and the IPv6 Tunnel that exists on this server.

NOTE: This series of steps does not use RRAS, and therefore there is no firewall on this router. Therefore these steps should be for lab environments only, as you need to ensure that Windows Firewall on all your endpoints is secure (remote admin [DCOM], RPC Endpoing and 445 have default rules for open to anyone) – these will need securing to a suitably valid range, or implment IPSec on the servers so connections cannot be made from non domain members. A good IPv6 port scanner is available at

Continuing in your elevated command prompt on the tunnel Windows machine enter the following command:

netsh interface ipv6 set route ::/0 IP6Tunnel publish=yes

This adds a route for the entire IPv6 address space to go via this machine, and publishes it so that it can be see by other machines on the LAN. The publish=yes command is the only bit of this that is different from the commands provided by Hurricane Electric.

The next command to enter is:

netsh interface ipv6 add address interface=”Local Area Connection” address=2001:xxxx:yyyy:65b::1

This command adds an IP address from the Routed /64 range to the network card on the machine (called “Local Area Connection” here. If your network card has a different name then change the name, and use the correct address that you want to use rather than the generic one I show here). I have chosen to end my routers IPv6 address with ::1. This means that the full address in my example is 2001:xxxx:yyyy:065b:0000:0000:0000:0001 and therefore I could choose anything for the 0000:0000:0000:0001 bit, remembering that one long list of zero’s can be collapsed to :: and leading zero’s can be removed.

Continue with:

netsh interface ipv6 set interface “Local Area Connection” forwarding=enabled advertise=enabled routerdiscovery=enabled advertisedefaultroute=enabled privacy=disabled

The command (which is long and probably wrapped on your web browser) enables forwarding on the Local Area Connection interface (forwards packets arriving on this interface to others, i.e. makes this box a router) and it will also advertise it’s routes and that it is a router. Router advertisement (both advertise=enabled routerdiscovery=enabled) allow clients on your network to find the router and generate their own IPv6 address. In this example this will therefore turn on IPv6 for your entire LAN. If you wish to do this test on just a few servers then add a valid IPv6 address using DHCPv6 with reservations or add the addresses manually on the machines you want to test IPv6 from (valid addresses are 2001:xxxx:yyyy:065b:z:z:z:z, where z:z:z:z is up to four blocks of four hex digits each). Privacy (see later) is disabled for this NIC as well.

NOTE: For any website that is IPv6 enabled, any computer that gets an IPv6 address will now use the tunnel to get to the internet. If the tunnel is down or slow then internet connectivity on all your machines will suffer. Your tunnel will be slower than your WAN speed and latency is likely to be higher. Consider carefully the advertise and routerdiscovery settings. You can always change them to disabled later if you wish (and reset your client network card to pick up the changes with netsh int ipv6 reset). I managed two days with IPv6 for every client before I changed back to IPv4. There are steps on line to change the prefix policy (netsh int ipv6 show prefix) to put IPv4 above IPv6 as an alternative to turning advertising and router discovery off.

The next command to enter is:

netsh interface ipv6 set route 2001:xxxx:yyyy:65b::/64 “Local Area Connection” publish=yes

This command publishes the route to your LAN so that the IP6Tunnel network that you created earlier can route packets to the correct interface. This is the opposite command the the first publish command you ran previously, as that one published the outbound route, this publishes the inbound route.

Finally you need to run this last command:

netsh int ipv6 set interface “IP6Tunnel” forwarding=enabled

This allows packets arriving on the IP6Tunnel from the internet to be forwarded to other networks on the machine. Again, this is the opposite of the earlier forwarding=enabled command and allows forwarding of packets arriving on the IP6Tunnel adapter to be forwarded into the LAN.

Connecting to the IPv6 Internet

Finally you are ready to go. If you open a command prompt on a Windows Vista or later client on the LAN and run ipconfig you should see an IPv6 address (and maybe a temporary IPv6 address) as well as a default gateway listing your newly configured router (reached via the Link Local address rather than the global IP address of the router if routerdiscovery is enabled on the router).

The IPv6 address you have is calculated from your Routed /64 subnet (the network portion of the address) and your MAC address. This local portion will therefore always be the same for you. This means that you are therefore trackable on the internet, as your local portion does not change. Therefore Windows 7 generates a temporary address which changes every 7 days (netsh int ipv6 show addresses and the Pref. Life column for Preferred Lifetime). After seven days the temporary address is recreated.

Open your web browser and visit to see if you have IPv6 connectivity.

You should now be able to ping or ping and get a response back from the IPv6 internet.

Note that if you reboot your router or your client they will take a short while to pick up a valid IPv6 configuration from the Router Advertisements (RADV) that are running on the router (advertising the Routed /64 range you have – no requirement for DHCPv6 in this example).

Having the IPv6 Internet Connect To You (i.e. Publishing IPv6 Services)

On any machine with a valid global IPv6 address you should be able to enable the File and Printer Sharing (Echo Request – ICMPv6-In) rule in Windows Firewall and then visit (or another IPv6 online ping test tool) and be able to ping your server or client.

Disable the ping firewall rule if needed and enable or create a firewall rule to allow a port of your choice to be published over IPv6. Configure the server to support listening on IPv6 if needed and then attempt to browse that service from another IPv6 enabled client.

Got this far – have a go at the IPv6 certification at Hurricane Electric

IPv6 Certification Badge for brainier