Route summarization in Detail with Scenarios

This Video brief about Route summarization.
Route summarization is a method where we create one summary route that represent multiple networks/subnets. It’s also called route aggregation or supernetting.
Summarization has a number of advantages:
¯ Saves memory: routing tables will be smaller which reduces memory requirements.
¯ Saves bandwidth: there are less routes to advertise so we save some bandwidth.
¯ Saves CPU cycles: less packets to process and smaller routing tables to work on.
¯ Stability: Prevents routing table instability due to flapping networks.
There are also some disadvantages to summarization:
¯ Forwarding traffic for unused networks: a router will drop traffic when it doesn’t have a matching destination in its routing table. When we use summarization, it’s possible that the summary route covers networks that are not in use. The router that has a summary route will forward them to the router that has advertised the summary route.
¯ Sub-optimal routing: routers prefer the path with the longest prefix match. When you use summaries, it’s possible that your router prefers another path where it has learned a more specific network from. The summary route also has a single metric.