Do I need two network cards for a Network Load Balancing (NLB) cluster?

A. Unlike Microsoft Cluster service clusters, in which you should have separate NIC's to separate regular traffic from the cluster heartbeat traffic, NLB members don't need multiple NIC's. However, many people still recommend two NICs in NLB servers, given the low cost of quality NIC's. Additionally, multiple network cards are desirable in the following situations:

  • For inter-host communication between NLB cluster members when operating in uni-cast mode. With only one NIC NLB members are unable to communicate directly with each other.
  • If the NLB members connect to back end services, for example a Microsoft SQL Server database, it might be desirable to use separate NICs to separate the front and back end traffic.
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