A summary of the CIDR experiments of RIP routing under Cisco

The enterprise that divides the subnet often should notice, the router load is heavier.

What is CIDR, abbreviation for no class inter-domain routing

Based on the VLSM subnet Division, the route entry is increased, the route "explodes", and the burden of routers increases.

When the size of the network is smaller, the problem does not seem very serious. But in a large network, if all the subordinate networks are split, this will make the routing table on the core location router become a huge branch. This data capacity can reach more than 10 MB or hundreds of MB, or even more! If the routing table of a router has hundreds of MB, if you want to see a specific route entry in the routing table, you will also find a specific route entry in the thousands of tens of thousands of routing entries, and the routing efficiency becomes very low. We can find some routing entries for the core routers that we test or view on the Internet, and it takes a long time to download the routing entries.

Routers find and update the routing entries, and the router's ability to process data is greatly reduced. This situation is becoming more visible in operators, and for the increasingly depleted IPv4 today, the continued dismantling of IP addresses is a major problem

To make it more efficient in a large scale network, routing totals are used. CIDR and vlsm are actually an inverse operation.

The following is an experimental topology

After a good configuration through the SH IP route, you can see that the R4 router has each subnet route, while the R5 router has only a 192.168.49.0/25 rollup route, all the routers through R5 to the rest of the R1~R4 can use this RIP route

R 192.168.49.0 [120/1] via 201.0.0.1, 00:00:02, SERIAL1/2

201.0.0.0/24 is variably subnetted, 2 subnets, 2 masks

Sends data to the outgoing interface s1/2. This has reached the speed of reducing routing entries and increasing the efficiency of viewing.

The key point of the routing rollup is the effect of the command IP summary-address RIP 192.168.49.0 255.255.255.128 configured under the interface S1/3 of the R4 router, and please understand it carefully.