Painting Road Signs and Other Long-Lasting Directions


It takes a long time to build a highway and even longer to build a new town or city. But whenever a new road is finally finished, some old road signs might need to be updated because there might be a better way to drive to some nearby town. Thankfully, because it takes a long time to build a road, the road signs do not have to be repainted very often.

With routers, the network engineer can do the equivalent of painting the road signs. To do so, the engineer can configure a static IP route, which is configuration for a router that tells the router to add a particular entry to its routing table. For instance, in Figure 12-2, R1 didn't have a route to subnet 150.1.3.0, meaning it couldn't forward a packet that was destined for IP address 150.1.3.3. In Figure 12-3, the engineer solved the problem by configuring a static route on R1 for subnet 150.1.3.0, with outgoing interface Ethernet2, and next-hop router of 150.1.2.2.

Figure 12-3. Painting a Routing Table with a Static Route


Before adding the static route, R1 did not know how to forward packets whose destinations were in subnet 150.1.3.0. Now R1 knows to forward those packets to R2 next.

Static routes work, but they can be a pain in the neck to maintain. Network topologies tend to change a lot more frequently than roads do, and static routes make it difficult to use all the possible routes to the same part of the network when you have multiple possible physical paths. As a result, most companies do not use static routes throughout their networks; instead, they use routing protocols, as described in the next section.




Computer Networking first-step
Computer Networking First-Step
ISBN: 1587201011
EAN: 2147483647
Year: 2004
Pages: 173
Authors: Wendell Odom

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