Role of the ip classless command

The role of the ip classless command is explained in the ip classless command book, but it is not clear. for the ip classless problem, give a simple example, assume that the following output C 10.1.1.0/24 s0/0 C 10.1.2.0/24 s0/1 S 10.1.3.0/24 s0/0 S 0.0.0.0/0 s0/1 is displayed in the route table. received the IP package, the destination address 10.1.4.1. How do I forward a vro? Q: How does the vro forward the received IP address, route 1.4.1? According to common sense, the default route is used. The answer is correct, but this is only when the ip classless command takes effect. If this command is removed, route 1.4.1 to the default route, and route 10.1.4.1 to the router! In this case, when the ip classless command does not take effect, the cisco router first looks for the route record to see which large network number the destination address is. For example, the large network number 10.1.4.1 is 10.0.0.0, because it is A Class A address, and then find the large network number or related records of its subnet in the routing table, if the corresponding records can be found, the forwarding will be discarded if not found. Why not use the default route? Because the router now thinks it knows all the subnets on the Class A address 10.0.0.0. In this example, there are only three subnets: 10.1.1.0/24, 10.1.2.0/24, 10.1.3.02/24, the subnet 10.1.4.0/24 to which the data packet is sent does not exist. Therefore, the data packet is discarded. The route entry to route 1.4.1 is different, because the route table does not have the route record of the large network number 255.0.0.0, so the default route is used immediately. Conclusion: The ip classless command is actually the method for finding the affected route table. The most direct effect is the use of the default route. With the ip classless command, the router uses the longest matching principle to find the route table, regardless of the class of the destination address.