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Windows 2003 NLB, not accessible from other subnet.

Posted on 2009-05-19
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Last Modified: 2012-05-07
Hi All,
Ive setup 2 web servers (each with 2 NICs) into one Windows NLB cluster.
Im able to access this cluster very well from same subnet front-end IP are, but not from other subnet.
Details-
ServerA-
Front-end-
IP 192.168.40.217
Subnet mask: 255.255.255.0
Gateway: 192.168.40.1

Backend
IP 192.168.13.49
Subnetmask 255.255.255.0
Gateway: Null

ServerB-
Front-end-
IP 192.168.40.218
Subnet mask: 255.255.255.0
Gateway: 192.168.40.1

Backend
IP 192.168.13.50
Subnet mask 255.255.255.0
Gateway: Null

NLB IP  192.168.40.219
Subnet mask 255.255.255.0

I need to load balance only Front-end NIC and back-end is only for SQL access.

Im able to access this NLB IP within 192.168.40.x subnet without any issues, and also able to see the NLB Manager showing all servers Converged. All settings default.
Cluster Operation Mode  Multicast
Defined Port rules: 0-65535
      Both,
      Multiple Host
      Affinity : Single


Please help me in this, not sure what am I missing.
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Comment
Question by:sandeepkulkarnib
3 Comments
 
LVL 17

Expert Comment

by:Andres Perales
ID: 24423896
Do you have a router any where in your network to do this type of routing?
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Accepted Solution

by:
oBdA earned 500 total points
ID: 24423903
Since you have two NICs in the nodes anyway, simply change the cluster mode to Unicast instead of Multicast. Most routers don't publish multicast addresses, so you'd have to manually create ARP entries for your NLB address.
Since you have two NICs, you'll still have inter-host communication even with the cluster in multicast.
Some links that might be of interest:

Unicast NLB nodes cannot communicate over an NLB-enabled network adaptor in Windows Server 2003
http://support.microsoft.com/kb/898867

Network Load Balancing: Configuration Best Practices for Windows 2000 and Windows Server 2003
http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/clustering/nlbbp.mspx

Network Load Balancing Frequently Asked Questions
http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/clustering/nlbfaq.mspx

How Network Load Balancing works
http://technet2.microsoft.com/windowsserver/en/library/3b98db33-e748-4a75-a0af-e445569655be1033.mspx?mfr=true

Network Load Balancing clusters
http://technet2.microsoft.com/windowsserver/en/library/98d46a24-96d8-412c-87d8-28ace62323d21033.mspx?mfr=true

Network Load Balancing Best practices
http://technet2.microsoft.com/windowsserver/en/library/fa6ef832-1aa7-472f-b492-0dd3c60bd46d1033.mspx?mfr=true

Using NLB with ISA Server - Part 2: Layer 2 Fun with Unicast and Multicast Modes
http://www.isaserver.org/articles/basicnlbpart2.html

Catalyst Switches for Microsoft Network Load Balancing Configuration Example
http://www.cisco.com/en/US/products/hw/switches/ps708/products_configuration_example09186a0080a07203.shtml
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