Novell BUSINESS CONTINUITY CLUSTERING FOR NETWARE 1.1 - ADMINISTRATION Manual page 75

The following figure illustrates a multihomed server with all nodes running a dynamic routing
protocol.
Multihomed Server Running a Dynamic Routing Protocol
Figure 5-1
1.1.1.1
1.1.1.2
Router 1
3.3.3.1
In this network, the server is a multihomed server hosting a critical network service. For simplicity,
assume that all nodes are running some dynamic routing protocol.
If the client attempts to communicate with the server with the 1.1.1.1 IP address, it will try to reach
the server through the nearest router, which is Router 1. If the 1.1.1.1 interface were to fail, Router 1
would continue to advertise reachability to the 1.0.0.0/FF.0.0.0 network and the client would
continue to forward packets to Router 1. Being undeliverable, these packets would ultimately be
dropped by Router 1. Therefore, in spite of the fact that the service is still up and running and can be
reached through the other active interface, it is rendered unreachable. In this scenario, a recovery
would involve the ability of the client application to retry the alternate IP address 2.2.2.1 returned by
the name server.
Now consider the same scenario but with the server configured with a virtual IP address and the
client communicating with the virtual IP address instead of one of the server's real IP addresses, as
shown in the following figure.
Server
X 2.2.2.1
Router 2
3.3.3.3
Client
2.2.2.2
3.3.3.2
Virtual IP Addresses 75