Category Archives: RD Gateway

In place upgrade of RD Gateway farm nodes to Windows Server 2016 removes the Loopback adapter for UDP load balancing

Posted on by
Reply

Here’s a quick heads up to anyone who’s involved in upgrading existing Windows Server 2012 (R2) RD Gateway farms to Windows Server 2016.

In my recent experiences the in place upgrade (VMs) works rather well. Just make sure the netlogon service is set to automatic (a know issue and a fix is coming) after you upgrade and install all updates. Also make sure that you don’t have this issue

Windows Time Service settings are not preserved during an in-place upgrade to Windows Server 2016 or Windows 10 Version 1607

There is however one networks specific issue specific you’ll need to deal with when leveraging UDP with a load balancer via Direct Server Return.

When you have a RD Gateway farm you load balance it with a (preferably high available) load balancer like a Kemp Loadmaster. I have described this in these blogs/videos Load balancing Hyper-V Workloads With High To Continuous Availability With a KEMP Loadmaster and Quick Demo Video Of Site Failover With KEMP Loadmaster Global Balancing

What you also do is load balance both HTTPS (TCP, port 443) and UDP (port 3391). For UDP we use Direct Server Return ((DSR) as described in my blog post Load balancing UDP for a RD Gateway farm with a KEMP Loadmaster. This requires a properly configured loopback adapter.

image

During the in place upgrade to Windows Server 2016 this loopback adapter is removed form the nodes. So you need to add it back just a described in my original blog post. Normally it will find the settings for it in the registry but it’s bets you check it all out as I’ve found that the loopback adapter did have “Register this connection”s address in DNS” enabled as well as NETBIOS over TCP/IP. So, per my blog post, check it all to make sure. Other than that, after installing all the Windows Server 2016 updates all works smoothly after an in place upgrade.

Hope this helps someone out there!

RD Gateway Management Console crashes with .NET framework 4.6.1 update (KB3102467)

Posted on by
16

 

UPDATE: KB – the June 2016 update rollup KB 3161606  June 2016 update rollup for Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2  contains the fix for this. See KB3162871 RD Gateway Manager console crashes with the latest .NET Framework 4.6.1 update on Windows Server 2012 R2 

Apparently the Exchange console and Skype for Business Server  2015 is not the only victim of Microsoft pushing out the .NET framework 4.6.1 update (KB3102467) to servers via Windows updates and WSUS. A colleague of mine described Windows updates as a game of Russian roulette, indicating there’s al least a QA concern …

The most recent victim I found was the RD Gateway management console on Windows Server 2012 R2. You might have the same issue on older Windows Versions but I’m only running W2K12R2 (it’s 2016 after all).

The result is that when you’re editing a Connection Authorization Policies or Resource Authorization Policies their membership settings (adding/removing groups) the MMC just crashes. Creating new ones is equally problematic!

image

You see the following errors logged in the event viewer:

Faulting application name: mmc.exe, version: 6.3.9600.17415, time stamp: 0x54504e26
Faulting module name: clr.dll, version: 4.6.1055.0, time stamp: 0x563c12de
Exception code: 0xc0000409
Fault offset: 0x00000000002fdbd8
Faulting process id: 0x12ec
Faulting application start time: 0x01d166820b2de977
Faulting application path: C:\Windows\system32\mmc.exe
Faulting module path: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\clr.dll
Report Id: 57bbb59c-d275-11e5-9440-00155dd2ca06
Faulting package full name:
Faulting package-relative application ID:

image

Followed by

image

The culprit once again is the .NET Framework  4.6.1 update (KB3102467)  for Microsoft Windows.

image

Get rid of that update to restore functionality. Come on Microsoft, Quality assurance! You need people to update ever faster for both security reasons and in order to keep up with technologies and the cloud cadence. You need to make sure they can do so without worrying all the time!

Load balancing UDP for a RD Gateway farm with a KEMP Loadmaster

Posted on by
5

When implementing load balancing for RD Gateway we must take care not to forget load balancing the UDP traffic. Now your RDP Connection will still work over HTTPS alone if you forget this, but you’ll miss out on the benefits.

  • Better experience of bad, unreliable network connections with high packet loss
  • Better experience with high end graphics and in general a better graphical experience over WAN links.

As many people have load balanced their gateways since Windows Server 2008 (R2) when UDP was not into play yet and as things work without people might forget. The most important thing you need to know is that when leveraging UDP for RDP 8/8.1 the UDP session traffic has to leverage Direct Server Return (DSR) for the real servers configuration when we configure load balancing for a RD gateway farm with a KEMP Loadmaster. I’m focusing on the UDP part here, not the HTTPS part. That’s been done enough and the Kemp info on that is sufficient. The UDP part could do with some extra info.

The reason for this is that when UDP is leveraged for high end graphics we want to avoid sending all that graphical network traffic the load balancer. There is no real added value being performed there in this UDP use case but the load might get quite high. This is where DSR is leveraged wen configuring the Loadmaster. That means we also need to configure our real servers to uses Direct Return as the forwarding method. When you forget this you’ll lose UDP with RDP 8.1 but you might not notice immediately. If you’re not looking for it as the HTTP connection alone will let you connect and work, albeit with a reduced experience.

To read more on why it’s done this way (even if it seems complex and has drawbacks) see http://kemptechnologies.com/ca/white-papers/direct-server-return-it-you/ you’ll notice that for graphics it is great idea. By selecting Direct Server Return as the  forwarding method (see later) changes the destination MAC address of the incoming packet on the fly (very fast) to the MAC address of one of the real servers. When the packet reaches the real server it must think it owns the VS IP address, which it doesn’t. So we use the loopback adapter to let the real server reply as if it does but we don’t respond to ARPs as that would cause issues with the load balancer who has the real IP of the virtual service. That’s where the 254 metric we configure in the demo below comes into play.  Note that  the real server responds over it normal NIC. Which is great and it helps with firewall rules not ruining the party. That’s why with DSR which leverages the the loopback adapter on the RD Gateway servers also requires you to configure the weak host / strong host behavior for the network configuration on those servers, it’s not answering itself! I’ll not go into details on this here but basically since Windows Vista and Windows Server 2008 the security model has change from weak host to strong host. This means that a system (that is not acting as a router) cannot send or receive any packets on a given interface unless the destination/source IP in the packet is assigned to the interface. In the “weak host” model, this restriction does not apply. Read more about this here. Let’s walk through this UDP/DSR/weak host setup & configuration.

On your Loadmaster you’ll create a virtual service for UDP traffic.

  • Select Virtual Services > Add New.
  • Enter the IP address of your RD Gateway Farm
  • Set 3391 as the Port.
  • Select udp for the Protocol.
  • Click Add this Virtual Service.

Open up the Standard Options to configure those

image

  • We don’t need layer 7 as the UDP connections are tied to the HTPP connection and they will spawn and die with that one.
  • We select Source IP Address as the Persistence Mode as the RD Gateway needs persistence to guarantee the connection stay together on the same RD Gateway server. Set the time out value no to high so it isn’t remembered to long.
  • We select least connections as that’s the best option in most cases, let the farm node with the least load take on new connections. This is handy after down time for example.

Now head over to the Real Servers section

image

  • Make sure the Real Server Check parameters is set to ICMP ping, which is what the LoadMaster uses to check if the RD Gateway servers are alive.
  • Click Add New to add an  RD Gateway server, you’ll do this for each farm member.

image

  • Enter the Real Server Address for each RD Gateway.
  • Enter 3391 as the Port.
  • Select Direct return as the Forwarding method.
  • Click Add This Real Server.

When you’re done it looks like this:

image

So now we need to check if the real servers are seen as on line and healthy …

image

If one RD Gateway server is down or has an issue you see this … no worries the LoadMaster sends all clients to the other farm member server.

image

Configure the  RD Gateway farm servers to work with DSR

We’re not done yet, we need to configure our RD Gateway servers in the farm to work with DSR.

Go to Device Manager, right-click on the computer name and select Add legacy hardware

image

Click next on the welcome part of the wizard …

image

Select “Install the hardware that I manually select from a list (Advanced)” and click Next …image

Scroll down to network adapters, select it and click Next …image

Under Manufacturer choose Microsoft and as Network Adapter scroll down to Microsoft KM-TEST Loopback Adapter, select it and click Next.

image

Click Next to install it …image

image

Click next to close the Wizard.image

 

Now go to  and change the name so you can easily identify the loopback adapter …imageimage

In the properties of the loopback adapter we disable everything we don’t need. In this case, we only need IPV4 and nothing else. We also need to configure the TCP/IP settings for the loopback adapter. So open up the TCP/IP v4 properties of that NIC …image

Enter the IP address of the Virtual Service for UDP on the load master and, very important enter a subnet mask of 255.255.255.255 for the loopback address. It’s a subnet of 1 host, the VIP IP address. Do not enter a gateway!

image

Now go to the advanced setting and deselect Automatic metric and fill out 254. This step prevents the server to respond to ARP requests for the MAC of the VIP with the MAC of the loop back adapter.

image

Also uncheck “Register this connection”s address in DNS” to avoid any name resolution problems for the real servers.

image

Finally disable NETBIOS over TCP/IP.

image

What we are doing with all the above is preventing any issues with normal network traffic to this real servers being affected by the loopback adapter who’s one and only function is to enable DSR and nothing else. It’s a bit “paranoid” but it pays to be and prevent problems.

Dealing with Strong Host / Weak Host setting in W2K8 and higher

We now still need to deal with the strong host security model and allow the LAN interface to receive traffic from the KEMP and allow the KEMP to receive and send traffic form/to the LAN interface. This is done by executing the following commands:

netsh interface ipv4 set interface LAN weakhostreceive=enabled
netsh interface ipv4 set interface KEMP-DSR-LOOPBACK weakhostreceive=enabled
netsh interface ipv4 set interface KEMP-DSR-LOOPBACK weakhostsend=enabled

That’s it. You should now have HTTP/UDP connections in your RD Gateway monitoring when using a load balancer and set it up correctly.  Remember if this isn’t configured correctly you’ll still connect but you lose the benefits the UDP connections offer.

Now another thing you need to be aware of in your RD Gateway configuration is that for UDP  to work with DSR is that the UDP Transport Settings need to be configured for “all unassigned” IP addresses. Other wise DRS won’t work and you’ll lose UDP. This make sense, you’ll receive traffic on the VIP on your real servers. It’s just like DSR with a web server where in IIS you’ll bind both the LAN and the loopback adapter to port 80 or 443 for the site.

image

We can see that one client is connected via RDSGW01 to two servers (Viking and Spartan) leveraging HTTP and UDP. The load balancing is done via the KEMP Loadmasters in  geo-redundant fashion.

image

Yes, my geo load balanced RD Gateway Server farms are providing UDP support for the servers and clients we  RDP in to.

image

Combined with those servers and clients being spread amongst the sites provides for enough business continuity to keep the shop running when a site fails, so it’s more than just connectivity!

Load balancing Hyper-V Workloads With High To Continuous Availability With a KEMP Loadmaster

Posted on by
1

I’m working on some labs and projects with KEMP Loadmaster load balancing appliances (LM 2400, LM-R320) That will lead to some blog post on  load balancing several workloads, which are all on Windows Server 2012 R2  Hyper-V or integrate in to Azure. The load balancers used in the labs are the virtual appliances, depending on the needs and environment these are a very good, cost effective option for production as well and depending on the version you get they scale very well. Hence their use in cloud environments, they will not hold you back at all!

To stimulate your interest in load balancing and high availability I’ve put up a video on load balancing RD Gateway services. Consider it a teaser or introduction to more about the subject.

Why use an appliance (hardware/virtual)? Well let’s look at the 2 alternatives:

  • Round robin DNS, which is also sometimes used is just to low tech for most real life scenarios and sometimes can’t be used or is less efficient which impacts scalability and performance. On top of that it doesn’t provide health checking for failover purposes.
  • I’ve also said  before that while Windows NLB  provides layer 4 load balancing out of the box it’s pretty basic. It also often causes a lot of network grief and the implementation can be tedious. This has not improved in an ever more virtualized & cloud based world. On top of that, when network virtualization comes into play you might paint yourself into a corner as those two don’t mix. But if that’s not a concern and you’re on a budget, I’ve used it with success in the past as well.