Understanding the network.pdf - Back to Home

Weaknesses of Static Routing
Static routing, sadly, has two weaknesses that are difficult to
overcome, the first of which becomes evident to most network
administrators when their networks start to grow. Static routing does
not scale. If you have 20 hosts connected to an Ethernet hub and a
1.544Mbps Internet link, static routing is just fine. If you have 30
high-speed routers and 128 IP subnets, static routing is not going to
work. Building 30 different routing tables to route traffic to 128
different subnets will not work in a clean and efficient manner.
The second weakness is rather ironic: What makes static routing so
reliable in small static networks is what makes them impractical to
use in large networks. Static routes are static! Static routing is not
adaptable. When a link fails, there is no means to redirect the traffic
being forwarded to the link. The absolute nature of static routes is
why most routers have a default gateway or route of last resort. In the
event that the dynamic routing protocol fails, it forwards the traffic to
the default gateway.
When static routes are used improperly, they can, at the very least,
affect network performance and, at worst, they can cause routing
loops or data loss due to traffic hemorrhages. With that in mind, use
of static routes in complex networks should be looked at in terms of
growth of the network and what effects will result if they are lost or
removed from the routing table.
NOTE
Do not underestimate the amount of bandwidth used by routing
protocols! In older shared segment networks, bandwidth is precious.
Protocols, like RIP, constantly send routing updates, even after the
network has achieved convergence.
NOTE
If you plan to use static routes in your network design, be sure to
document on your network map which routers contain which routes
and to what devices. This will be a large asset when you or someone
else (who did not design the network) is troubleshooting network
problems.