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What is Floating Static Route ?

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  • Last Updated : 22 Aug, 2022
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Floating Static Route means we are going above the distance of the dynamic default route. In other words, floating static routes are used as provisory code in any case if the main working route goes down or fails. Floating static routes are commonly employed where the static routes are configured with an advanced executive distance than the selected primary route ones and it would not be in the routing table until the primary route fails.

So primarily here we are configuring a static route with an advanced executive distance the dynamic route begins employed in the location of the static route and will be used as a part of the backup.

First, we will configure the network topology in the Cisco packet tracer:

Step 1: Open packet tracer and create network topology using these devices:

S.NO Devices Model Name
1. PC PC
2. switch PT-Switch
3. Router PT-Router

Arrange our network topology something like this:

In this Topology, we have a starting point which is PC0 with network id 192.168.10.0, and a destination which is PC1 with network id 192.168.60.0.

We have to reach from starting point to destination for that we have two paths:

  • Router 3: Primary route by priority so packets flow through from host to router0 to router3 to router1 and then finally PC1(destination).
  • Router 2: secondary route by priority so packets flow through from host to router0 to router 2 to router 1 and then finally PC1(destination). this will work if the primary route goes down or shut down.

 

Then we’ll configure PCs with IP and default gateway according to the IP addressing table given below:

S. No Device name IPv4 address Subnet Mask Default Gateway
1 PC0 192.168.10.2 255.255.255.0 192.168.10.1
2 PC1 192.168.60.2 255.255.255.0 192.168.60.1

 

 

Checking by sending PDU from starting point to the destination we will not receive a reply because we have not assigned static routes till now. 

 

As we can see from the above image destination host is unreachable.

Step 2: Let’s configure the interfaces (routers) with IP addresses using the IP address table provided below: 

IP addressing Table (router0):

S. No Device name Interface fa0/0  interface se2/0 interface fa1/0
1. router0 192.168.10.1 192.168.20.1 192.168.40.1

CLI commands to configure router0 :

Router>en
Router#conf t
Router(config)#int fa0/0
Router(config-if)#ip add 192.168.10.1 255.255.255.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface FastEthernet0/0, 
changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0,
 changed state to up
Router(config-if)#int se2/0
Router(config-if)#ip add 192.168.20.1 255.255.255.0
Router(config-if)#no shut
%LINK-5-CHANGED: Interface Serial2/0, changed state to down
Router(config-if)#int fa1/0
Router(config-if)#ip add 192.168.40.1 255.255.255.0
Router(config-if)#no shut

IP addressing Table (router1): 

Device name Interface se2/0 Interface fa1/0 interface fa0/0
router1 192.168.30.1 192.168.50.1 192.168.60.1

CLI commands to configure Router1:

Router>en
Router# conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#int se2/0
Router(config-if)#ip add 192.168.30.1 255.255.255.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface Serial2/0, changed state to up
Router(config-if)#int fa1/0
Router(config-if)#ip add 192.168.50.1 255.255.255.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface FastEthernet1/0, 
changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet1/0, 
changed state to up
Router(config)#int fa0/0
Router(config-if)#ip add 192.168.60.1 255.255.255.0
Router(config-if)#no shut

IP addressing Table (router2):

Device name Interface Se2/0 Interface se3/0
router2 192.168.20.2 192.168.30.2

CLI commands to configure router2:

Router>en
Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#int s2/0
Router(config-if)#ip add 192.168.20.2 255.255.255.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface Serial2/0, 
changed state to up
Router(config-if)#
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/0, 
changed state to up
Router(config-if)#int se3/0
Router(config-if)#ip add 192.168.30.2 255.255.255.0
Router(config-if)#no shut

IP addressing Table (router3):

Device Name Interface fa0/0 Interfacefa1/0
router3 192.168.40.2 192.168.50.2

CLI commands to configure router3:

Router>en
Router#conf t
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#int fa0/0
Router(config-if)#ip add 192.168.40.2 255.255.255.0
Router(config-if)#no shut
Router(config-if)#
%LINK-5-CHANGED: Interface FastEthernet0/0, 
changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, 
changed state to up
Router(config-if)#int fa1/0
Router(config-if)#ip add 192.168.50.2 255.255.255.0
Router(config-if)#no shut

Now, all of the interfaces are configured successfully and the network will look like this in packet tracer:

 

As of now, only devices are configured with IP addresses but we have not assigned static routers. so, to send packets from starting point to the destination we have to assign routes to the interfaces and prioritize the path by adding admin value.

Commonly, If we assign an interface with primary routes then packets will go through the primary path but if any case primary path blocks then that case packet will flow around and reach its destination via the secondary path.

For Example:

If we are assigning routes to router2 then, we have to add commands in CLI something like in this format:

Router(config)#ip route <network id><subnet mask><next hope network id>move towards starting point
Router(config)#ip route <network id> <subnet mask> <next hope network id> <admin value>  move towards destination point

admin value to make secondary route

Router(config)#ip route 192.168.60.0 255.255.255.0 192.168.40.2  (primary route)
Router(config)#ip route 192.168.60.0 255.255.255.0 192.168.20.2 10 (secondary route)

Let’s assign static routes to router0 by adding typing these commands to CLI:

Router0 static routes:

Router(config)#ip route 192.168.60.0 255.255.255.0 192.168.40.2 ?
 <1-255>  Distance metric for this route
 <cr>
Router(config)#ip route 192.168.60.0 255.255.255.0 192.168.40.2 
Router(config)#ip route 192.168.60.0 255.255.255.0 192.168.20.2 10

Router1 static routes:

Router(config)#ip route 192.168.10.0 255.255.255.0 192.168.50.2
Router(config)#ip route 192.168.10.0 255.255.255.0 192.168.30.2 10

Router2 static routes:

Router(config)#ip route 192.168.10.0 255.255.255.0 192.168.20.1
Router(config)#ip route 192.168.60.0 255.255.255.0 192.168.30.1

Router3 static routes:

Router(config)#ip route 192.168.10.0 255.255.255.0 192.168.40.1
Router(config)#ip route 192.168.60.0 255.255.255.0 192.160.50.1

After assigning static routes to the specific interfaces network is well configured so now we will check by sending packets and pinging the destination IP address whether it gives replies or not:

 

 

The above image illustrates how packets travel from beginning point to destination through the primary designated path.

How does the Floating Static Route Will Work:

Let’s say we block or shutdown one channel from the primary path for example:

Router1 interface Fa1/0

by tying these commands in CLI:

Router(config)#in fa1/0
Router(config-if)#shutdown

As we can in the below image the way from router1 to router3 is blocked so the packet will follow the secondary path to reach its destination which is PC0.

 

when the transferred packet comes back from destination to host it will follow a secondary path:

 


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