How-To: Configure Network Load Balancing (NLB) with Two Network Adapters

1. Assign appropriate IP addresses to each NIC, placing the NICs in separate
subnets. Rename the first NIC “Public“ and the second to “Admin“, do this for each machine.

* Node1 –

o “Public” NIC
* IP address: 10.10.10.11
* Subnet: 255.255.255.0
* Gateway: 10.10.10.1
* DNS: as appropriate

o “Admin” NIC
* IP address: 192.168.1.1
* Subnet: 255.255.255.0
* Gateway: N/A
* DNS: N/A


* Node2 –

o “Public” NIC
* IP address: 10.10.10.12
* Subnet: 255.255.255.0
* Gateway: 10.10.10.1
* DNS: as appropriate

o “Admin” NIC
* IP address: 192.168.1.2
* Subnet: 255.255.255.0
* Gateway: N/A
* DNS: N/A

2. On the “Public” NICs, click “Advanced” and add an additional IP address
as the Virtual IP Address which clients will connect to from the Public
network (i.e. – 10.10.10.169)

3. Install “Network Load Balancing” as an additional service from the
“Public” adapter properties.
* Click “Install..” and then select “Service” in the upper-window and
click “Add.”
* Select “Network Load Balancing” in the upper-window and click “OK”
* Answer any prompts and provide the correct path to installation media (Windows 2000 installs only).

4. Once NLB is installed, return to the Properties page for the “Public”
NIC and select the check-box next to “Network Load Balancing.”  This
enables the service globally.

5. Next, select the item “Network Load Balancing” and click “Properties”

6. Configure the NLB Cluster properties according to your parameters,
using the following example steps as a guide.

* Node1 –

o “Public” NLB Cluster Parameters tab
* Primary IP address: 10.10.10.169
* Subnet: 255.255.255.0
* Full Internet Name mail.clusterhelp.com

o “Public” NLB Host Parameters tab
* Priority: 1
* Dedicated IP address: 10.10.10.11
* Subnet: 255.255.255.0


* Node2 –

o “Public” NLB Cluster Parameters tab
* Primary IP address: 10.10.10.169
* Subnet: 255.255.255.0
* Full Internet Name mail.clusterhelp.com

o “Public” NLB Host Parameters tab
* Priority: 2
* Dedicated IP address: 10.10.10.12
* Subnet: 255.255.255.0

7. MultiCast support can be optional in this configuration, though I would not recommend it.

8. You can also now take time to create a static Host record (A record) in
your scenario’s DNS infrastructure to provide appropriate name resolution
to the NLB cluster name (i.e. – mail.clusterhelp.com or just mail).

9. Your NLB cluster should be up and running after the nodes converge.

10. An external client should now be able to ping the IP address of the
NLB cluster (i.e. – 10.10.10.169) as well as each of the individual node
addresses (i.e. – 10.10.10.11 & 10.10.10.12).

11. Many good diagnostic commands can be found by typing “wlbs /?” in a
command window.  For example, “wlbs query” shows the status and
convergence state of the cluster. If you are running Windows Server 2003 (any version expect SBS) you can use the graphical Network Load Balancing Manager – I love this tool.

12. IMPORTANT NOTE: In this configuration, each individual node is NOT
able to ping the other node’s Public physical IP address (i.e – 10.10.10.11
cannot ping 10.10.10.12 and vice-versa).  I believe this is expected
behavior, as the NLB cluster is now responding to requests on the Virtual
Cluster address (i.e. – 10.10.10.169).

Written by Ryan Sokolowski (blogged with permission) – with minor changes and tweaks

24 thoughts on “How-To: Configure Network Load Balancing (NLB) with Two Network Adapters

  1. I did exactly as the article stated, even used the same IP address range. Before activating NLB every machine in a 3 node cluster could ping all NICs on all machines.

    Once I enabled NLB on each of the public NICs, none of the machines coudl ping each other. This is in an isolated lab environment with only the three nodes connected together via a giga switch.

    Good old Windows 2003 server huh!

  2. I don’t understand then how NLB knows to use the 192.168.100 adapters for inter-array communications. The reason this is important is:

    a) I want to make sure that I am not hitting my subnet with multicast traffic from NLB

    b) Even more importantly I have another application using a 3rd nic on each machine that is 192.168.101 and its traffic must be seperate from the NLB traffic. So how will NLB pick which nic to use for the back end traffic?

    Thanks

  3. The 192.168.100 adapters are not used for inter-array communications – only the NLBed 10 NICs are.

    Only the 10 network has NLB on it.

    Anything 192 will be seperate.

  4. Hi all!
    I’m novice here and that’s why I need some help.
    Can you give me some info and some links where I can find general help on using forum.
    I think that this info can be usefull not only for me.
    Thanks a lot!

    P.S. Pardon me for my making this topic in wrong section
    ____
    Dallas…I’m lovin’ it 🙂

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  10. I didnt understood how the NLB is identifies the private IP. and how the Virtual IP recognizes the hearbeat of the nodes.

  11. I have one more doubt whether i need to configure cable between two servers for heartbeat or cable between switch to servers

  12. Hello,

    I really like the clarity of your example. I have one question though, what is the purpose of having the 192.x.x.x.x card setup? Is this just for Administrative tasks (ping, vpn)? Or does it also take part in serving HTTP requests?

    Thanks.

  13. Can i configure network load balancing with 2 differance public IP addresses in the same gateway says:

    Dear all IT experts

    I belived that some one may know about this, so please help…

    Thanks in advance

  14. sir
    i required to config xp pc as router when three nw are connected which is two wired nw is internet having fix ip add and one is private nw so whenever any nw is down next nw is automatic connected.
    regards
    msc

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