Upgrading and Repairing Networks

Building Redundancy into the Network

It doesn't matter what kind of support maintenance contract you have with your vendor if it takes the vendor hours or days to get the parts necessary to replace a failed system. For this reason, it's a good idea to build redundant paths in your network from the design phase so that, for example, if a router goes down, another path through the network will allow users to keep accessing the data they need. Providing for fault-tolerant servers using clustering technology also can be used to ensure maximum uptime for critical systems.

	In Chapter 2, "Overview of Network Topologies," you will find a good discussion of using partial-mesh topologies to build redundancy into your network. See "Mesh Topology" (p. 17) and as they pertain to redundancy, "Building and Campus Topologies" (p. 23) and "Multi-Tiered Network Topology" (p. 26).

If the time needed to get replacements is excessive (when compared to the cost of paying idle users, the overhead involved in office space, and so on), it might be wise to keep a duplicate device on-site so that you can swap it into service to replace a failed device in an emergency. In the case of a router or switch, it's easy to replace the failed device, follow a carefully written plan to reconfigure it, and put the network path back in service.