This post provides an overview of static routes and concepts related to Administrative Distance. In the topology which I have created below, a new router (Singapore) is connected to Manila via their respective Serial interfaces. Two serial interface were used to connect routers between Manila and Singapore. Primary link will be via Serial 3/2 and Secondary link will be via Serial 3/3. The default AD will be used in the primary link and the an AD of 50 will be set up in the secondary link.
Concepts of Floating Static.
- A floating static route is not permanently entered in the route table.
- It appears only under the special circumstance of the failure of a more-preferred route.
- This second link has been added for redundancy: If the primary link fails, floating static routes will direct traffic across the backup link.
- An administrative distance specifies the preferability of the means by which the route was discovered.
- Static routes pointing to a next-hop address have an administrative distance of 1.
- Static routes referencing an exit interface have an administrative distance of 0.
On Singapore Router, an administrative distance of 20 ( by default the next hop address without specifying the AD is set to 1) were set to all routes via the 10.1.20.1. Meaning this will be the alternative path if the primary link fails.
The results of the “show ip route static” shows that in order to reach 10.1.5.0 subnets, it has to go through the Manila router serial interface Serial 3/2 (10.1.10.1)
The traceroutes from the computer connected in Singapore router shows the traffic path is via the gateway 10.1.10.1
By disabling the primary link of the Manila or Singapore router, the traffic will be shifted to the secondary link. As observed the AD number have changed to 50 from the results of the “show ip route static”.
As seen from the traceroutes, it shows that the traffic to reach the destination is now via the backup link which was set up using the floating static (using a higher administrative distance).
By enabling back the primary interface, the routing table will update with the preferred gateway
NETWORK LESSON 
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