Updating routing tables is necessary when changes occur on networks, such as disconnections, or when new subnets are added. The methods for updating routing tables include static updates (in which administrators write in the routing table configuration manually) and dynamic updates, which involve the use of routing protocols on the routers in a network that detect changes, notify neighboring routers of the changes, and determine the best route to configure for the change then write the change to the routers involved. If I was the administrator of a small network that had no more than three routers I would enable the RIPv2 routing protocol so that routing updates would occur dynamically rather having to manage them statically for each device. The advantage in enabling RIPv2 is that the protocol is very simple to configure and require little or no management and yet provides dynamic updates on networks that even include VLSM and subnets. The disadvantage is that the protocol is limited in scope (up to 15 router hops) so is not useful if the network grows beyond the RIPv2 limitations. RIPv2 also adds additional traffic to the network and can also introduce security issues if not configured correctly.

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On networks with over three network devices (routers and layer 3 switches) routing protocols make configuration easier. Routing protocols also perform a lot of work automatically such as changing routes when it is detected that a link has failed. Routing protocols also make convergence (updating routing tables) much faster by performing the updates automatically vs. having to update static routes manually when a failure occurs. So routing protocols help to keep the network available but they also have a cost. Routing protocols require indepth planning and configuration and this becomes more involved as the networks get larger and more complex when integrating networks (especially if more than one routing protocol is involved).

Static routes still have their place. On servers for example that have more than one network interface, you need to configure static routes to tell the server which interface to send through for some destiinations. Static routes are quite common on routers that are configured to connect to an ISP because there are only two devices on the network (in that case the router and the network device for the ISP (usually a router of some sort). Essentially static routes should be used when you want full control over the routes entered on a device, you do not want the routes to change, the routes do not change often, or when the administrative cost is higher with a routing protocol than a static route.