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2008 R2 RDP NLB setup

Posted on 2013-12-02
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I have two 2008 R2 Remote Desktop servers. Both have dual NICs.
Server 1 - NIC 1: 10.33.1.110  NIC 2: 10.33.1.91
Server 2 - NIC 1: 10.33.1.111  NIC 2: 10.33.1.92
At this point I can ping all these addresses from another client. I can RDP into any of these addresses as well.
I add the NIC 2 IPs to an NLB cluster and assign the cluster 10.33.1.90.
The moment I do this, from any client I can no longer ping the NIC 2 addresses or the cluster address and RDP only works on NIC 1.

I can ping .90 .91 and .92 from Server 1 or Server 2 but not from any client.
What am I missing?
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Question by:scarpenter104
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by:scarpenter104
ID: 39691745
I changed the cluster from unicast to multicast and it started working, so I'll modify my question: why does this not work in unicast?
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by:Mahesh
ID: 39691966
For that you need to understand difference between unicast and multicast NLB

In unicast actual network card MAC is getting overlapped with original MAC address
When you add two servers in unicast mode, both network cards MAC is replaced by virtual MAC
Technically you can't communicate within nodes having same MAC address
Thats why you need to use two network cards in case of unicast NLB

As opposed, in Multicast, virtual MAC is appended to original MAC address of members
So, you have two MAC addresses on network card. One is its own and another is virtual MAC
obviously two servers can communicate with eath other even if you have single network card
You can check ipconfig /all properties of unicast nlb servers and multicast nlb servers for proof

http://technet.microsoft.com/en-us/library/cc782694(v=ws.10).aspx
http://social.technet.microsoft.com/Forums/forefront/en-US/969f37a0-6838-4d1d-a56a-e35aa9a780f5/when-to-use-nlb-unicast-or-multicast?forum=Forefrontedgegeneral
http://ptgmedia.pearsoncmg.com/images/0789728494/webresources/A011203.html

Mahesh
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by:scarpenter104
ID: 39693391
Your information is a little dated as 2008 R2 does not require two network cards any more to do unicast. That is also irrelevant since I am using two NICs.

Unfortunately, this doesn't address the question of why unicast does not work in this situation while multicast does. I'm starting to think it may be related to the fact that the servers are running in a Virtualbox environment (something I neglected to add).
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Mahesh earned 500 total points
ID: 39693888
There are enhencement in windows 2008 R2 NLB but basic principle remains the same.
You can use 1 adapter in unicast with limitations.
Its not changed.
Unicast with Single Network Adapter - The MAC address of network adapter is disabled and the cluster MAC address is used. Traffic is received by all nodes in the cluster and filtered by the NLB driver. Nodes in the cluster are able to communicate with addresses outside the cluster subnet, but node to node communication within cluster subnet is not possible.
Unicast with Multiple Network Adapters - The MAC address of the network adapter is disabled and the cluster MAC address is used. Traffic is received by all nodes in the cluster and filtered by the NLB driver. Nodes within the cluster are able to communicate with each other within the cluster subnet and also with addresses outside the subnet.


http://www.techotopia.com/index.php/Building_a_Windows_Server_2008_Network_Load_Balancing_Cluster
http://technet.microsoft.com/en-us/library/cc725691.aspx - new features in 2008 R2

I have also seen that Unicast NLB is running with one adapter properly without limitations, but only in Vmware \ Hyper-V virtual machines, because virtualization change the original concept somehow
Since you have physical adapter intact on physical host, it is able to manage virtual guest with 1 NIC in NLB without limitations.

You already have 2 NICs per server, in that case ur unicasting must work technically.
Like you said try to toggle virtual box network settings, it might help.

Mahesh
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by:scarpenter104
ID: 39791119
This issue was never actually resolved, although I believe the unicast problem is due to a failure in VirtualBox to handle things properly. I have left  this open for quite some time hoping that I or someone else could shed more light on the issue, but at this point I think I will just close it and reward Mahesh for his efforts.
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by:scarpenter104
ID: 39791120
Not a solution, but a lot of research and information.
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by:Mahesh
ID: 39791156
Yes, you are absolutely right
Practically on physical servers having NLB you can't communicate between Unicast NLB members as there MAC address is same, but with NLB VIP external systems can communicate with them and then requests get routed to NLB members.

when virtualization is came to picture as weather you do unicast with one NIC, those are fake \ virtual network cards only and hyper-v \ VMware \ other virtualization software  will manage to work with them somehow (because hypervisor host network adapter is intact) but its actually workaround and some times you might face issues.

In case of VMware virtual machines, they recommends multicast NLB with single NIC
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1556
http://social.technet.microsoft.com/Forums/exchange/en-US/d231d1e0-30f0-4a1e-8226-18a705b715c1/windows-nlb-vmware-e2k10-cas-array?forum=exchangesvravailabilityandisasterrecoverylegacy
http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006580

In case of Hyper-V, there is known issue exists with Unicast NLB
http://blogs.technet.com/b/networking/archive/2010/02/12/cannot-access-the-virtual-or-dedicated-ip-address-of-an-nlb-node-guest-running-in-unicast-mode-on-windows-server-2008-r2-hyper-v.aspx

The purpose of above articles, there may be bug having with Virtual Box as well
You can check with there support blog as i have not worked with Virtual Box

Mahesh
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