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NLB for terminal server not working

Posted on 2011-09-27
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Last Modified: 2012-06-22
I have 3 win 2k3 servers that I want to use NLB  as a terminal server farm. These are all VMs on vsphere, and I know that shouldnt make much of a difference.

I was going to use multicast, as that seemed to be the best way.

I installed NLB on each server, then set the cluster IP and the cluster name on each, set them to multicast, and then set the priority.

The MAC it shows seems to be the same for 2 of the machines, and the 3rd is different.  After I added this to the 3 machines, when I connect to the cluster, only 1 allows connections, when I look at the other 2, it states acquiring network address.  It gives an IP Conflict message,

I did add (as per the insructions I saw) the cluster IP into each server as a 2nd IP after installing the NLB.

I ended up having to turn off the NLB from 2 of the machines, and let just one of them keep the cluster IP so people could still connect to it.  I am not certain of what is going wrong.  I was able to ping each of the servers actual IP address, and could reach each via RDP before the NLB config.

I have a cisco 3750 switch, and I did add an static arp statement, which pointed to what I assume was the cluster MAC, each server showed the same MAC for the most part, but one had 01, and 2 had 02 as the first characters in the MAC.  I used what they gave, but replaced the first 2 characters with 00 for the arp statement.

Any ideas??
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Question by:Wayside_Tech
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noci earned 999 total points
ID: 36713632
Switches are designed with the assumption that MAC addresses are unique world wide.
So having seen on packet from one system, that would indicate wich portshould be used.

Switching between ports can cause a lot of problems with packets ending up in the wrong session.
AFAICT a HUB should be useed for this type of configuraton

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Assisted Solution

by:Kareem_ElBably
Kareem_ElBably earned 501 total points
ID: 36714348
why dont you use Unicast mode with 2 network cards it is much better
also check ARP configuration on the link below

http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a0080a07203.shtml
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by:Wayside_Tech
ID: 36716247
Since these are VMs, it would be challenging to have the ports connected to a hub before the switch.   The problem with unicast is the same, as per Vmware, they should be in multicast mode.  If they were physical machines, I could understand that..
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by:Wayside_Tech
ID: 36716250
One thing I noticed, is that there is an admin tool for NLB, is that a better choice to use to setup the cluster instead of individually on each server?
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by:noci
noci earned 999 total points
ID: 36716537
Then the mac-addresses need to have an odd first byte, that bit signals the presence of multicast traffic.
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Expert Comment

by:noci
ID: 36716539
I meant the effective MAC addresses for the cluster alias.
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by:Wayside_Tech
ID: 36716713
how do I determine what the cluster MAC would be?  I didnt see it anywhere.  I assumed what it was, but not sure.
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by:Wayside_Tech
ID: 36906167
I figured it out.  NLB display gave me all sorts of stats, and I used the NLB manager to get it up and running and it works great.
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Author Closing Comment

by:Wayside_Tech
ID: 36906176
i figured it out on my own, assigning points because they are earned,,...
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Expert Comment

by:noci
ID: 36906248
Thanks.
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