Static, Default, and Floating Static Routes

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Plain-English explanation

Static routes are manually configured — predictable, low overhead, no protocol chatter. Use them for small networks, default routes to ISP, or specific summary paths.

A default route (0.0.0.0/0) matches everything not matched elsewhere — the "gateway of last resort."

A floating static is a backup static route with higher administrative distance (AD) than the primary. It sits idle until the primary (lower AD) disappears from the routing table.

Deep dive

Static route syntax:

ip route [network] [mask] [next-hop-IP | exit-interface] [distance]

Default static:

ip route 0.0.0.0 0.0.0.0 203.0.113.1

Floating static example: Primary OSPF route AD 110 active. Backup:

ip route 10.0.0.0 255.0.0.0 192.0.2.2 200

AD 200 > 110 — used only if OSPF route lost.

| Use case | Static fit | |----------|------------| | Stub remote site | Default to HQ | | Internet edge | Default to ISP | | Backup link | Floating static | | Full mesh enterprise | Usually dynamic instead |

Step-by-step — stub site default route

Branch router BR1: LAN 10.50.0.0/24 on Gi0/0, WAN to HQ 198.51.100.2/30 on Gi0/1.

interface GigabitEthernet0/0
 ip address 10.50.0.1 255.255.255.0
!
interface GigabitEthernet0/1
 ip address 198.51.100.1 255.255.255.252
!
ip route 0.0.0.0 0.0.0.0 198.51.100.2

HQ advertises internal routes via OSPF; BR1 only needs default for reachability.

Commands to know

Static and default routes

ip route 172.16.0.0 255.255.0.0 10.1.1.2 ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0 203.0.113.1 ip route 10.20.0.0 255.255.0.0 192.0.2.2 200

Verify

show ip route static show ip route 0.0.0.0

Troubleshooting

| Issue | Cause | |-------|-------| | Static not in table | Wrong next-hop unreachable, interface down | | Default route loops | Missing specific routes upstream | | Floating never activates | Primary never truly removed — track objects beyond CCNA | | Host can't reach Internet | Missing default on edge or host gateway wrong |

Static routes do not fix wrong next-hop reachability — verify L2/L3 to next-hop first.

Exam relevance

Exam trap

Lower AD wins. Floating static must have higher AD than the primary route to act as backup only.

Next-hop on multi-access

On Ethernet, static route via exit interface alone can cause issues — prefer next-hop IP when ARP is required.

Practice checklist

Configure static route and verify in routing table
Add default route on stub router lab
Configure floating static with AD 200 and test failover conceptually
Explain when static beats dynamic for a two-router lab
Complete Week 4 static routing lab

What destination and mask define a default route?

A floating static route uses administrative distance 250. The primary OSPF route uses AD 110. When is the static used?