An IPv6 Floating Static Route is simply an IPv6 static route that is used as a backup route. In this lesson, we'll cover the concept of a floating static route and configure it.
If you haven't viewed the lesson Static Routing – Be Careful!, consider reading it before moving forward with this lesson.
By default, a static route has an AD is 1. So to create a floating static route, we increase the AD of an alternate static route so that it is higher than a route that is already in the routing table for that same destination.
Floating static routes can be a backup for another static route or a route learned through a dynamic routing protocol. It's the administrative distance that's the key, not how the route was learned.
With static routing, when the local link to a route in the routing table fails, it will be automatically removed from the routing table. If the floating static route has the next best administrative distance, it will be inserted into the routing table.
Pro Tip: Static routing has no mechanism to detect an interface failure on the other side of the link. This is a significant disadvantage of static routing.
In the above topology, the path from R-1 to R-3 is the primary route. This makes sense because it is the path with the least number of hops. It has the default Administrative Distance of 1.
R-1>R-2>R-3 is the backup route. The AD from R-1 to R-2 has an AD of 10. By giving this route a higher AD than a route already in the routing table (R-1 to R-3 has an AD of 1), it's what's called a floating static route.
Configuration and Verification
For our lab we'll use the following topology:
Let's begin by configuring and verifying a static route so R1 has a route to R-3's Loopback 36 interface. A return route from R-3 to R-1 isn't required because it's directly connected.
R-1(config)#ipv6 route 2001:36::36/128 2001:13::3 R-1#sh ipv6 route static S 2001:36::36/128 [1/0] via 2001:13::3
This looks good. We've got our Static route in the routing table with the default Administrative Distance of 1.
Let's ping the loopback from R-1 to R-3's Lo36:
R-1#ping 2001:36::36 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2001:36::36, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/8 ms
Fantastic. The primary route is set.
Next, let's create an alternate route to and from R-1 and R-3's Lo36 interface. This path will be R-1>R-2>R-3. R1>R2 and R3>R2 will have a static route with an AD of 10. This will cause these routes to be floating static routes since they are for backup. They will only be inserted into the routing table when the primary route fails.
First, configure R1's route from R1>R2 with an AD of 10: