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When configuring NLB, you choose the cluster IP. This removes any other secondary IP addresses for the network adapter.

How can I have one cluster IP shared by NLB while still having multiple dedicated IPs to single machines, ie for the mail server?

EDIT more info:

Currently have Web1 serving the following: -> -> -> ->

Want to add Web2 to load balance/provide redundancy just for ->, while keeping and at Web1.

Reason for this is you only want your emails going to one inbox and the support website uses a MySQL db on Web1 which I don't want to mirror to Web2.

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A server using NLB will always have two ip addresses: the cluster ip address and a dedicated ip address. I'm not following what you are stating\asking. Can you clarify? – joeqwerty Nov 10 '10 at 0:02
Thanks @joeqwerty, added more info – user59135 Nov 10 '10 at 0:21
you have to configure the hosts with a unique IP, say and; then assign as the "nlb cluster" IP. Both hosts will then use both IPs. (This of course is the really simplified version). This MS Article describes it better: – Chris S Nov 10 '10 at 1:41
Thanks @Chris but how would I still have dedicated IPs just going to Web1 for mail, support and ns? – user59135 Nov 10 '10 at 9:55
up vote 1 down vote accepted

I've never seen your scenario with NLB but I'm thinking that you'll need to use multiple network adapters in the server. One for NLB traffic and one for everything else. I'm thinking that you'll need to set the non-NLB adapter to have a default gateway and not the NLB adapter, or you'll need to set a different metric on each adapter. This snippet from an MS TechNet article seems to address this, but I'm not completely sure:

Q. I Have Two Network Adapters on Each Server in My NLB Cluster. How Do I Ensure That All Outbound Traffic Goes Through Non-Load-Balanced Network Adapters?

A. Sometimes it is desirable for performance or other reasons to direct all outgoing traffic through a different network adapter that the one that is being load balanced with NLB. This implies that there is more than one network adapter on each host in a cluster: NLB is bound to one network adapter called cluster network interface card, and the other network adapter does not have NLB bound to it. To make sure that the outbound traffic leaves each host through the non-cluster network adapter, do the following:

Set the metric on the cluster network adapter to a higher value than the non-cluster network adapter. For example, if you have two network adapters on each host, set the non-cluster network adapter metric to 1 and cluster network adapter metric to 2. The network adapter with a higher metric means it is more expensive to use than the other one with a lower metric. That will ensure that the outbound traffic will be routed out of the non-cluster network adapter.

If you want to use default gateways on both cluster and non-cluster network adapters, make sure the metric of the default gateway on the cluster network adapter has a higher value than the one on the non-cluster network adapter. If you do not want to route any outgoing traffic out of the cluster network adapter, you should not specify the default gateway for it at all.

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