Lesson Overview and Learning Objectives

Static routing is the manual installation of routes in a router routing table. It is predictable, simple, and extremely important for small networks, default routes, backup paths, and special routing requirements. This lesson uses the same logic for both IPv4 and IPv6 so students can see exactly what is common and what changes between the protocols.

By the end of this lesson, you should be able to:

  • Explain how a router uses longest-prefix match, administrative distance, and metric when choosing routes.
  • Configure and verify IPv4 and IPv6 default static routes.
  • Configure and verify IPv4 and IPv6 network static routes.
  • Configure and verify IPv4 /32 and IPv6 /128 host routes.
  • Build floating static routes that operate as backup routes using a higher administrative distance.
  • Distinguish recursive, directly attached, and fully specified static routes.
  • Use Cisco IOS/IOS XE verification and troubleshooting commands to isolate static-routing failures.

CCNA focus - Do not memorize only the syntax. Be able to read a routing table and determine why a particular static route is installed, ignored, preferred, or used as a backup.

 

1. Static Routing Fundamentals

1.1 What is a Static Route?

A static route is a route that an administrator manually configures. Unlike a dynamic routing protocol, the router does not learn the destination from OSPF, EIGRP, RIP, or BGP. The route remains configured until it is removed, changed, or becomes unusable because its next hop cannot be resolved.

A static route tells the router three basic things:

Which destination prefix should match the packet.

Where the packet should be sent next - a next-hop address, an exit interface, or both.

Optionally, what administrative distance should be associated with the route.


1.2 Why Use Static Routing?

A static route is a route that is manually configured by a network administrator rather than learned automatically through a dynamic routing protocol such as OSPF, EIGRP, or BGP.

Static routing gives the administrator direct control over the path used to reach a destination network.

Use case

Why static routing fits

Small/stub networks

Few destinations and little topology change.

Default route

Send all unknown destinations toward an ISP or upstream router.

Backup path

Floating static route can take over if a preferred route disappears.

Management / host route

Force a very specific destination to use a controlled path.

Lab / troubleshooting

Predictable behavior makes path analysis easier.


1.3 Static Route Advantages and Limitations

Advantages

Limitations

Simple and deterministic

Does not automatically discover topology changes.

No routing-protocol CPU/bandwidth overhead

Configuration effort grows with network size.

Easy to control exact path

Human error can create black holes or loops.

Useful for backup routes

Return routes must also be considered.


2. How a Router Chooses a Route

2.1 Longest Prefix Match Comes First

When more than one routing-table entry matches a destination, the router chooses the route with the longest matching prefix. A /32 host route is more specific than a /24 network route, and a /24 network route is more specific than a /0 default route.

Candidate route

Specificity

Example result

0.0.0.0/0

Least specific

Used only when no more-specific IPv4 route matches.

192.168.30.0/24

Network route

Preferred for all addresses in 192.168.30.0/24 over the default.

192.168.30.50/32

Host route

Preferred only for 192.168.30.50.


2.2 Administrative Distance

Administrative distance (AD) ranks different sources of routing information for the same destination prefix. Lower is preferred. A normal Cisco static route has a default AD of 1. A floating static route deliberately uses a larger AD so another route is preferred while it exists.

 


2.3 Metric

Dynamic routing protocols use metrics to choose between routes learned by the same routing protocol. Traditional…