Cisco Certified Network Associate (CCNA) 200-301 · Free study guide

Objective 3.3 — Configure IPv4 and IPv6 static routes

Static routes express deliberate reachability without a dynamic routing exchange. Their simplicity makes intent visible, but the operator owns next-hop correctness, failover design, and change maintenance.

Default routes

An IPv4 default uses 0.0.0.0/0; an IPv6 default uses ::/0. It matches only after no more-specific route does. A branch commonly points default traffic toward an upstream router, while that upstream still needs a return route for branch prefixes. One default is not bidirectional design.

Network and host routes

A network static covers a supplied prefix such as 192.0.2.0/24 or 2001:db8:20::/64. A host static uses /32 for one IPv4 address or /128 for one IPv6 address. Host routes can create surgical exceptions, but too many specific entries increase operational burden.

Next-hop and interface forms

A route can specify a next hop, an exit interface, or both, depending on platform and media. On multiaccess Ethernet, a next-hop address gives the router a specific neighbor to resolve. On point-to-point links, an exit interface can be sufficient. A fully specified route can make both explicit.

For an IPv6 link-local next hop, include the exit interface because link-local addresses repeat across links. Ensure the next hop itself is on-link and reachable.

Floating static routes

A floating static uses an administrative distance higher than the primary route's source. It remains absent or less preferred while the primary is installed and becomes active after primary withdrawal, if its own next hop is usable. Setting a higher metric inside unrelated syntax does not create the intended preference.

IOS command map

An IPv4 network route follows the form ip route 203.0.113.0 255.255.255.0 192.0.2.2; append an administrative distance, such as 220, only when the design intentionally makes it float behind a better route. An IPv4 default is ip route 0.0.0.0 0.0.0.0 192.0.2.2. For IPv6, use ipv6 route 2001:db8:20::/64 2001:db8:10::2 or ipv6 route ::/0 2001:db8:10::2. A route whose next hop is link-local also needs the intended exit interface.

Use show ip route static and show ipv6 route static to confirm installed routes, then inspect the exact destination with show ip route 203.0.113.0 or the corresponding IPv6 lookup. Verify next-hop resolution and forwarding in both normal and backup states; a line visible in running configuration may be absent from the active routing table.

Worked scenario

R1 learns 203.0.113.0/24 through OSPF at distance 110 and has a backup WAN next hop 192.0.2.2. Configure the same prefix statically with a distance greater than

1. Verify OSPF wins normally, then in an authorized lab remove the primary path

and confirm the static enters and forwards. Restore the path and confirm preference returns.

Verification

Inspect configuration and the active IPv4 or IPv6 table. Confirm route prefix, distance, next hop, and resolution. Test a destination inside the route, not only the next hop. For floating behavior, validate both steady states and convergence under controlled conditions. Check the reverse route and security policy.

Common traps

• Writing the destination host address with a network prefix incorrectly.
• Assuming a configured route must enter the table.
• Forgetting exit-interface context for an IPv6 link-local next hop.
• Giving a backup static a lower distance than the primary.
• Testing only one direction.

Readiness checklist

• I can configure default, network, host, and floating routes.
• I can use IPv4 and IPv6 forms accurately.
• I can explain next-hop recursion.
• I verify normal, failure, and recovery states.