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Providing Fault Tolerance to Multiple NICs with Different Addresses

Novell Cool Solutions: Tip
By N Subramanian

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Posted: 14 Jan 2004

Providing fault tolerance to multiple NICs bound to different network addresses is not possible in NetWare. Currently providing fault tolerance to multiple NIC bound to the same IP address and same Net/subnet is possible.

Solution: In NetWare 6.5, Virtual IP Address is an IP Address that is bound to a ?Virtual NIC? ( i.e., a NIC that has no real physical existence.) To the TCP/IP Stack, the ?Virtual NIC? behaves as any other real NIC. Conceptually, ?Virtual NIC? and ?Virtual IP Addresses? can be thought of as a logical extension to the conventional ?Loopback Interface? and ?Loopback Addresses?. But functionally they are used for providing Fault Tolerant host access to Multi-homed hosts with more than one physical NIC in case of Host Interface Failures. Virtual IP address provides fault tolerance to multiple NICs bound to different NICs.

For example, configure VNIC board through inetcfg and assign a virtual IP address (which is on different network from the IP address provided to the physical interface) to the configured VNIC board. The media type for the board will be VNIC. From there on communication happens to the machine through the Virtual IP address. Thus, despite physical interface failures, a virtual IP address on a multihomed server acts as an always-reachable IP address of the server.

In general, it can be said that if a connection between two machines is established using a virtual IP address as the end-point address at either end, the connection will be resilient to interface failures at either end.

For more info, look here in the documentation.

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