In the topology
![](https://www.atlink.fr/wp-content/uploads/2019/07/image-26.png)
Router R3 receives 1.1.1.1/32 route information from R2
![](https://www.atlink.fr/wp-content/uploads/2019/07/image-27.png)
This route gets next into the routing table
![](https://www.atlink.fr/wp-content/uploads/2019/07/image-28.png)
But what if R2 installed another protocol or source same route (same subnet and mask) to R1 loopback0 network ?
![](https://www.atlink.fr/wp-content/uploads/2019/07/image-29.png)
R2 starts poisoning the R1 route in its updates to R3
![](https://www.atlink.fr/wp-content/uploads/2019/07/image-30.png)
And the route is deleted from the RIP database and routing main table
![](https://www.atlink.fr/wp-content/uploads/2019/07/image-31.png)
For a RIP learnt route to be advertised downward it has to be in the routing table first