Single network interface card limitations with WLBS

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If you disable multicast support and are only using unicast, you should install a dedicated network interface card (NIC) to handle cluster traffic to achieve optimum performance and the full range of networking functionality. Although it is possible to have a successful cluster installation with only one NIC, there are two limitations to this approach:

• Computers within the cluster will not be able to communicate among themselves with any networking protocol, not just TCP/IP. This can be a special problem if one or more of the clustered servers also act as primary and backup domain controllers.
• Networking traffic destined to individual servers within the cluster will generate additional networking overhead for all computers in the cluster.

These limitations may not be important for many installations. If the computers within the cluster are only accessed from outside the cluster (that is, there are no intracluster communications) and noncluster communications are infrequent (for example, short nightly updates of the Web server content to individual computers in the cluster), the use of a single networking card should be sufficient. Also, it is always possible to test and demo Windows NT Load Balancing Service (WLBS) using a single network card prior to installing additional cards for operational purposes.