Any solution for NLB clusters and unknown unicast flooding...

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Nov 6th, 2005
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I think you might be already aware about unknown unicast flooding issue with NLB clusters. In brief, the issue is as follows...

L-3 Router - L-2 switch - cluster nodes

L-3 router learns only NLB cluster MAC address and whereas L-2 switch learns individual cluster nodes MAC address but not NLB cluster MAC address. Due to this, if any input packet comes destined to a cluster node IP, then L-3 router encapsulates final frame with dest MAC address as Cluster MAC address and send to L-2 switch.

As L-2 switch can neither learn nor have NLB cluster MAC address, it treats all those packets as unknown unicast packets and sends to all ports in that particular VLAN. This is really a big issue if you have multiple clusters in single VLAN and scalability issue if you would like to have one VLAN per cluster (Imagine 100 clusters).

Is there any solution found for this? I saw in several articles that this is known issue and apply segregate into VLAN/cluster is the solution. Do you have any other ideas?

Thank you in advance...



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