Thank you for your question. The exclusion of the subnet mask in the EIGRP configuration on Router 3 is intentional and follows the behavior of the EIGRP routing protocol. In EIGRP, when using the network command, the subnet mask is optional. If omitted, EIGRP assumes a default subnet mask of 0.0.0.0, meaning that only the exact IP address specified in the command is considered. For example: router eigrp 1 network 10.0.0.0 In this case, EIGRP will include only the exact network 10.0.0.0/xx in its routing process. This approach is often used when you want to enable EIGRP on a specific network without specifying a range. It simplifies the configuration and is a common practice in EIGRP deployments. If you have any further questions or if there's anything else you'd like clarification on, please feel free to ask.

You can use it in any case within an autonomous system. However it's usually used in large environments with lots of routers since EIGRP only does incremental updates to routing tables so that keeps bandwidth usage and CPU, ram usage lower than OSPF for example. EIGRP is Cisco proprietary protocol so it might not work outside Cisco devices as well as it would in only Cisco environments. OSPF is an open standard and works better between multiple different manufacturers.

Hi Sorry for the pain. Your comment is the reason i stopped making video after this . JK NM 😉😉😂😂

Hi Sorry for the pain.