Overview:
A floating static route is a static route with an administrative distance higher than that of the routing protocol in use. In this way, the floating static route will only appear in the routing table if the existing static or dynamic route is lost.
Study Notes:
- Floating static routes are static routes with the administrative distance specified
- Floating static routes administrative distance is purposefully set higher than the preferred dynamic routing protocol
- Floating static routes act as a backup route should the preferred dynamic routing protocol lose its neighbor relationships and therefore have its routes removed from the routing table
- When the dynamic routes are removed from the routing table, the floating static route is inserted into the routing table since it has the next best administrative distance
- The command to add a floating static route is:
ip route <network-to-route-to> <subnet-mask> <next-hops-ipv4-address> <chosen-admin-distance>
- For example, if RIP is the preferred dynamic routing protocol than you know it has an administrative distance of 120. To create a floating static route that would take effect in the event RIP fails, you would enter the following command with an admin distance of 121 or greater:
ip route 192.168.1.0 255.255.255.0 172.16.1.1 121
- Floating static routes will also work to prefer one circuit over another
- For example, if you have one circuit that is 100Mbps and another that is 45Mbps you might want to set a static route over the 100Mbps circuit. It’s admin distance is 1. Then you’d set a floating static route to go across the 45Mbps circuit with an admin distance of 2 or higher. If the 100Mbps circuit goes down, the static route will be removed from the routing table and the floating static route will be used.
Labs:
PacketTracer Lab: CCNA-3.8.d-Floating-static-route.pkt
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