Cisco CCNA CCNP Certification Exam Tutorial Floating Static Routes
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Cisco CCNA/CCNP Certification Exam Tutorial: Understanding Floating Static Routes
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Overview
Mastering the configuration of floating static routes is crucial for both Cisco certification exams and practical networking. Let’s delve into how these routes work, using an example with R1 and R2 networks.
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Introduction to Floating Static Routes
Floating static routes are a smart solution for network redundancy. If you're curious about how they "float," keep reading!
Network Setup
In our scenario, R1 and R2 operate under OSPF on a Frame Relay network (172.12.123.0/24) and are connected via a BRI ISDN link (172.12.12.0/24). R1 advertises a loopback network, 1.1.1.1/32, through OSPF. The goal is to ensure R2 maintains a route to this loopback, even if the Frame Relay link fails. Enter the floating static route.
How It Works
R2 can successfully ping the loopback interface via OSPF:
```plaintext
R2
show ip route ospf
1.0.0.0/32 is subnetted, 1 subnetsO 1.1.1.1 [110/65] via 172.12.123.1, Serial0
```
Pinging confirms connectivity:
```plaintext
R2
ping 1.1.1.1
Success rate is 100 percent```
Administrative Distances (AD)
Understanding the AD is crucial. OSPF has an AD of 110. We can configure a static route with an AD higher than 110. Thus, it will activate only if the OSPF route becomes unavailable. This is why it's called a "floating" route?"it only appears in the routing table under specific conditions.
Configuring the Floating Static Route
Normally, a static route's AD is 1 or 0, both lower than 110. To change this, specify the desired distance in the `ip route` command:
```plaintext
R2(config)
ip route 1.1.1.1 255.255.255.255 bri0 111
```This slight increase ensures the static route remains inactive until needed.
Testing the Configuration
When the Serial0 interface is shut down, observe the routing table changes:
```plaintext
R2(config)
int s0
R2(config-if)shutdown
```The log confirms the OSPF route's removal:
```plaintext
%OSPF-5-ADJCHG: Neighbor Down: Interface down or detached
```
The floating static route now appears:
```plaintext
R2
show ip route
S 1.1.1.1 is directly connected, BRI0```
Verifying Connectivity
Despite the primary link's failure, traffic continues to reach 1.1.1.1 over the ISDN link. When OSPF re-establishes, the original route resumes:
```plaintext
R2(config)
int s0
R2(config-if)no shutdown
```R2’s routing table reflects:
```plaintext
O 1.1.1.1 [110/65] via 172.12.123.1, Serial0
```
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Conclusion
Floating static routes provide a reliable backup path without activating until necessary, keeping the ISDN link dormant and cost-effective. Always check the ISDN status to confirm expected behavior using `show isdn status`.
By mastering these techniques, you enhance your Cisco certification exam readiness and fortify your practical networking skills.
You can find the original non-AI version of this article here: Cisco CCNA CCNP Certification Exam Tutorial Floating Static Routes.
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