Floating Static Route Configuration On Cisco Routers
Floating Static Route is a Static Route that has a different Administrative Distance (Preference) that its default value. As you know, the default administrative distance of Static Routes is 1. So, Static Routes are the routes that are always selected as best route if we compare it with all routing protocols. But, there is a solution to change this in networking World. This solution is called Floating Static Routes. With Floating Static Routes, we can change the AD of the route. Here, we ill focus on IPv4 Floawting Static Routes. In another lesson we will learn IPv6 Floating Static Routes.
Routers selects Best Paths according to the Administrative Distance values. If the destination network is not directly connected (Its administrative distance is 0), router selects Static Routes to this destination. But sometimes,m this behaviour is not effective. For example if we have multiple routes to a destination and the route that we define with static route is not effective, then we do not want to go through that way. By changing its default Administrative Distance with a higher value, we maket his routes less prefered routes in router languge. So, they stay but they do not used without a failure in the other effective routes.
Let’s explain this with a scenario.Think about that we have three routes to a destination. One is learned by OSPF, the other is learned by EIGRP and the other is defined as static route. Normally, the admnistrative distances of these two rotues are like below:
- OSPF 110
- EIGRP 90
- Static 1
According to the best path algorithm of the routers, Static Route is selcted as Best Path, and the traffic goes through this path. If it fails, EIGRP path is selected and then if this way also fails, OSPF path is selected. To change this behaviour, we can define a Floating Static Route instead of this Static Route. For example, we can give an Administrative distance 150 to this floating static route and in this new situation, this route is not selected as Best Path. Instead, the routing protocol that has the lowest Administrative Distance is elected as Best Path. In our scenarios, this is EIGRP.
To configure Floating Static Route, we use the same command that we use in Static Route. Floating Static Routes are already Static Routes. The only difference is, with Floating Static Routes, we will give an extra Administrative Distance value to manuplate Route Selection.
In this scenario the destination network is 10.0.0.0/24. And our gateway is 10.10.10.1. And we will give 150 as Administrative Distance.
Router # ip route 10.0.0.0 255.255.255.0 10.10.10.1 150
To check the Floating Static Route selection we can use “show ip roıute static” and “show ip route 10.0.0.0” command.
Router # show ip route static
S 10.0.0.0/24 is directly connected, Ethernet0/0/0
Router # show ip route 10.0.0.0
Routing entry for 10.0.0.0/24
Known via “static”, distance 150, metric 0 (connected)
Routing Descriptor Blocks:
* directly connected, via Ethernet0/0/0
Route metric is 0, traffic share count is 1
We can also check the Routing Table with “show ip route” command to check the selected Best Path.
You can find the Administrative Distance values for Cisco below: