What are static routes, and when would you use them instead of a dynamic routing protocol?

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A static route is a manually configured routing entry that tells a router how to reach a specific destination network. Unlike dynamic routes that are automatically learned from other routers, static routes are explicitly defined by a network administrator and do not change unless someone modifies or removes them.

The syntax for configuring a static route on a Cisco router is ip route followed by the destination network, subnet mask, and either the next-hop IP address or the exit interface. For example, ip route 192.168.2.0 255.255.255.0 10.0.0.2 tells the router to send traffic destined for the 192.168.2.0/24 network to the next-hop router at 10.0.0.2. A default route is a special static route that matches all traffic: ip route 0.0.0.0 0.0.0.0 10.0.0.1 sends all traffic without a more specific route to 10.0.0.1.

Static routes have several advantages. They are simple to configure and understand. They consume no bandwidth for routing protocol updates. They are completely predictable since the path never changes unexpectedly. And they have the lowest administrative distance (AD 1) of any configured route, so they are preferred over dynamic routes to the same destination.

Static routes are ideal in several scenarios. Small networks with only two or three routers where the overhead of a routing protocol is unnecessary. Stub networks that have only one path in and out, such as a branch office with a single WAN link. Default routes pointing to an ISP, since you typically do not need to learn the entire internet routing table. Backup routes (floating static routes) with a higher AD configured to activate only if the primary dynamic route fails. And specific policy routes where you want to guarantee that traffic to a particular destination always follows a specific path.

However, static routes have significant limitations. They do not adapt to network changes. If a link fails, the static route continues to point to the unreachable path until an administrator manually updates it. In large networks with many routes and frequent topology changes, managing static routes becomes impractical and error-prone. There is also no built-in redundancy or failover unless you configure multiple static routes or floating static routes.

A floating static route is a static route configured with a higher administrative distance than the primary dynamic route. For example, if OSPF (AD 110) provides the primary path to a destination, you can configure a static route with AD 130 as a backup. Under normal conditions, the OSPF route is preferred. If the OSPF route disappears, the static route activates automatically.

The general recommendation is to use static routes for simple, stable paths and default routes, and to use dynamic routing protocols for larger networks where automatic convergence and redundancy are needed.