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TechKnowSurge Catalog Videos DEMO: Floating Static Route
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DEMO: Floating Static Route

Floating static routes provide automatic failover by assigning a higher administrative distance to a backup route, keeping it dormant until the primary path fails. This topic covers how to configure a floating static route on a Layer 3 switch to redirect traffic through a secondary link when the default route becomes unavailable.

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About this video

A floating static route is a redundancy technique used to maintain network connectivity when a primary path fails. It works by configuring a secondary static route with a manually elevated administrative distance, which causes the router to prefer the primary route under normal operating conditions and hold the backup route in reserve. Since static routes have a default administrative distance of 1, any value greater than 1 can be used to designate a route as the floating backup, with a higher number indicating lower preference. In a practical configuration on a Layer 3 switch, the process involves adding a second default route pointing to the backup next-hop IP address and appending the desired administrative distance at the end of the command. The routing table will continue to show only the primary route as long as that path remains reachable. Once the primary interface is shut down or loses connectivity, the router automatically installs the floating static route in its place and begins forwarding traffic through the backup link. Verifying the behavior requires examining the routing table with show ip route at each stage of the process — before configuration, after adding the floating route, and after simulating a failure by shutting down the primary interface. When the primary route is restored, the router reverts to it automatically, removing the floating route from the active table. This failover mechanism provides a straightforward way to implement path redundancy without dynamic routing protocols.

What you'll learn

What's covered

Floating Static Route

Aligned to

Cisco CCNA
3.3 Configure and verify IPv4 and IPv6 static routing
3.1 Interpret the components of routing table
3.2 Determine how a router makes a forwarding decision by default

Key terms

Static Route
A routing table entry manually configured by an administrator that specifies a fixed path to a destination network and never changes unless the administrator modifies it. Static routes are simple and predictable but do not adapt automatically to network topology changes.
Floating Static Route
A static route configured with a higher administrative distance than the primary route, functioning as a backup that activates only when the preferred route is removed from the routing table.
Active Directory
AD
Microsoft's directory service used to manage users, computers, and resources in a network.
Default Route
A catch-all routing entry represented as 0.0.0.0/0 (IPv4) or ::/0 (IPv6) that a router uses to forward packets when no more specific matching route exists in the routing table. It is typically configured to point toward the next-hop router or ISP connection.
Layer 3
The Network layer of the OSI model, responsible for logical addressing and routing packets between networks.
Failover
The automatic switching to a redundant system or component when the primary one fails.

Topics

Static Routing Floating Static Route Administrative Distance Route Failover Layer 3 Switching Networking

Transcript

The Scenario

In our example right here, we're going to say that we have a backup link and it's meant for just being a backup link. We don't want it to be utilized unless our main link goes down, and that's where we would want to use something like a floating route.

In our scenario we're on this layer 3 switch right now, and what we want to do is create the backup link to the Pi. Currently, right now, the default route points to router 1, and we want to use that unless it goes down — then we'll point to this demo Pi.

Configuring the Floating Static Route

I'm going to get onto the router here. I can do a show ip route and see how it's configured right now, and we see this static default route right there.

I'm going to get into the global configuration mode and configure another one. So ip route, and it's quad 0, so 0.0.0.0 space 0.0.0.0, and then the IP address we want to go to, so 10.1.10.21 is the IP address of that Pi.

Next, what we need to do is — we don't want this to take over the other static address or share with the other static address — so we've got to change the administrative distance. We can see that we just plug a number into here for the administrative distance. Now, since a static route has an administrative distance of one, it could be anything over one, so I'm just going to choose five. I'm going to hit enter.

Now let's see what our routing table looks like, and we can see that it still points to the other one.

Testing the Failover

If we were to take that down — let's go ahead and do a no ip route 0. I'm not sure if I've got this right, so I'm going to do a show run and take a look at the ip route here to make sure I get the command exactly. I'm going to type in no, and I'll come up here, and the one that I want to take out is this one right here, so I'm going to do no for that command. Now I do show ip route, and I can see the other one is installed with the administrative distance of five. So there you have it.

The other thing I could actually do to test this out is I can put this back in. So I'll do a do show ip route — that one's up — and then I can get into that interface and shut that down. Which interface is that? I take a look at my VLANs here. I believe it's VLAN 9, so I'm going to do a shutdown on this interface right here. So interface vlan nine, and I'm going to do a shutdown.

Let's take a look at that routing table now: show ip route. In fact, it has put that back into place. So we see that when the other interface goes down and it no longer has access to that network, then it will switch, and now it's directing this default route towards the Pi. If I want to bring that up I can do a no shut, and then take a look again, and we're back to normal here.

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