EIGRP Summarization

EIGRP support two types of summarization: auto-sum & manually sum on interface-mode.
- By default, auto summarization is enabled on interface
- To understand the behavior of EIGRP when auto-sum & manually sum is configured on Router, we will examine 2 cases:
Case1: summarized subnet (192.168.3.0) is different major from network between R1& R2 (192.168.1.0)

+ If auto-sum is enabled: R2 has 192.168.3.0/24 only
+ If auto-sum is enabled, manually sum network 192.168.3.0/30 on int s1/0 of R1 => R2 routing table contains both 192.168.3.0/30 & 192.168.3.0/24 routes
Case2: summarized subnet (192.168.1.0) belong to the same major from network between R1& R2 (192.168.1.0)

+ If auto-sum is enabled: R2 has 192.168.1.0/30. There is no network 192.168.1.0/24. In this case, auto-sum has no effect.
+ If auto-sum is enabled, manually sum network 192.168.1.0/28 on int s1/0 of R1 => R2 routing table contains that summarized route (192.168.1.0/28)