In this tutorial, we will take a CCNA exam question based on the routing table entries. We will learn how routers select a specific route to reach a destination address.
Refer to the exhibit. Which type of route does R1 use to reach host 10.10.12.10/32?
Router1#show ip route
Gateway of last resort is 10.10.10.22 to network 0.0.0.0
10.0.0.0/8 is variably subnetted, 4 subnets, 3 masks
C 10.10.10.0/30 is directly connected, FastEthernet0/1
O 10.10.12.0/25 [110/6656] via 10.10.10.1, 04:28:31, FastEthernet0/1
C 10.10.10.16/30 is directly connected, FastEthernet0/24
O 10.10.12.144/28 [110/110] via 10.10.10.1, FastEthernet0/1
B* 0.0.0.0/0 [20/0] via 10.10.10.22, 02:21:24
Let us understand all options in detail.
Routers take the default route when no other routers are available in the routing table. Since a route for the given address is available in the routing table, the router will not use the default route. Hence, the option A will be incorrect.
A floating static route is a static route that has a manipulated AD value. Routers use the letter S to represent a static route in the routing table. Since the routing table does not contain any static routes, the option D will also be incorrect.
A host route is a route that belongs to a specific host. In slash notation, a host route always has the value 32 after the slash. Since this routing table has no host routes, the option C will also be incorrect.
This tutorial is part of the tutorial series "Understanding route types in the routing table.". Other parts of this series are the following.
Chapter 1 The show IP route command on Routers
Chapter 2 Routing table updating methods
Chapter 3 Directly connected routes and Local routes
Chapter 4 Static and Floating Static Routes Explained
Chapter 5 Static and Dynamic routes in the routing table
Chapter 6 Default Route in the Routing Table
Chapter 7 Network Routes and Host Routes Explained
A network route is a route that belongs to an IP subnet. If a host route to the destination address is available, the router always uses it to reach the destination. If a host route is not available to reach the destination address, the router uses the network route. If a network route is also not available, it uses the default route. If the default route is also not available, the router discards the packet. In this example, since the network route is available to reach the destination address, the router will use it. Hence, the correct answer to this question will be option B.
That's all for this tutorial. In this tutorial, we solved a CCNA exam question and learned how routers use the routing table entries to make forwarding decisions.
