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CCNA – Floating Static Route

This lab will cover the topic 3.8.d Host Route from the Cisco Certified Network Associate (CCNA) blueprint. It will test your understanding and knowledge of configure floating static routes on Cisco IOS devices. Please use the initial configurations as a template for your lab utilizing whatever console means you have (GNS, Physical Gear, VIRL, etc).

FloatingStaticRoute


In this lab we will be looking at the use of Floating Static routes as a means of learning how Administrative Distance populates a routing table and how it can be used for fault tolerance. The only router configuration will take place on is R1. Routers 2 and 3 have been pre confured with all necessary elements. We will be using PC1 in the 10.1.1.0/24 subnet and PC2 in the 172.16.2.0/24 subnet. To successfully complete this lab static routes must be entered into R1 in such a way that the path between PC1 and PC2 goes through R2 unless there is a power failure on R2. In this case R1 should automatically switch over to the path through R3.

To start, look at R1’s routing table to check whether a route already exists to the 172.16.2.0 subnet.

Since we don’t have one we will create our first static route, and point it towards the next hop of R2.

Since this route is now in place, lets verify the routing table on R1 includes the route.

We can see that the PC does reply and that we are taking our desired route going through R2. We will now add our floating backup route. To do this we must keep in mind administrative distances. Using the table below we will come up with an administrative distance appropriate for our use. It must be bigger than 1, keeping in mind that if it is smaller than the AD of other routes to our destination. that we may want to use

Distances:
1 – Static
20 – External BGP
90 – EIGRP (Internal)
110 – OSPF
120 – RIP
170 – EIGRP (External)
200 – Internal BGP

With this in mind we will utilize a distance of 10. Since we are not working with any dynamic routing protocls we do not need to worry about being lower than the options listed in the table.

Notice that if we check the routing table at this point, we do not see our new route towards R3. This is because our new route has an Administrative Distance of 10, while our original route towards R2 has an Administrative Distance of 1. Remember, if two routes have the same length match, the route with the lower Administrative Distance will be selected fro the routing table.

We can see that our path is still indeed taking the R2 route by using another traceroute.

Now we can simulate a failure of R2. In this case I simply powered it off for simplicity. (Please note, in some tools such as GNS3 you may have to shut the link down on R1 that was pointing to R2 as well). With R2 shut down we will verify our floating route, the route with an AD of 10, is now in the routing table.

If we do another traceroute we can see that our PC is now taking the new path through R3. As you can see, the floating route provides us with a means of providing a form of fault tolerance without intervention in the case of an outage on R2. While there are other ways, some better, to accomplish this fault tolernce. This lab provides a fundamental look at how leveraging Administrative Distance can be useful, as well as how Administrative Distance is used to populate the routing table.

R1

R2

R3

Matt Ouellette is a certified information technology professional residing in Southwest Michigan. His technology findings and advice can be found on his PacketPilot blog. Mr. Ouellette spent 4 years as an I.T. Technician before stepping into a Network Engineer role at Bronson Health Group. Since completing his Associates Degree in Network Administration Matt has taken a head on approach to career enrichment through obtaining credentials such as CCNP, CCNA Voice, MCSA: Server 2008, and VCP5. This passion for continued learning allows him to deliver up to date quality technical solutions.

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