[Day 9] 1. Exclusive Features of EIGRP and Commands

Auto Summarization in EIGRP automatically summarizes routes at classful network boundaries, reducing the routing table size by merging multiple subnets into a single classful network address.
However, enabling auto summarization can lead to suboptimal routing if networks are disjointed.
Example: Consider two subnets, 192.168.1.0/24 and 192.168.2.0/24, connected through different routers. If auto-summary is enabled, both subnets might be summarized as 192.168.0.0/16 when advertised. This can cause incorrect routing as the routers may treat both subnets as part of the same network, resulting in incorrect forwarding, routing loops, or traffic being directed to the wrong destination.
To enable auto-summary:
```
auto-summary
```
(enabled by default). To disable it:
```
no auto-summary
```
.

Bandwidth management in EIGRP is important to ensure routing updates don’t consume excessive network bandwidth.
EIGRP allows you to control the bandwidth percentage used for routing updates with the "Bandwidth Percent" feature, which limits the percentage of available bandwidth an interface can use for EIGRP updates.
By default, EIGRP uses up to 50% of the interface bandwidth.

Over-utilization: On low-bandwidth links, using 50% can lead to congestion for other traffic.
Under-utilization: On high-bandwidth links, it might not fully utilize available bandwidth, potentially slowing down routing convergence.
Inaccurate Bandwidth Setting: Misconfigured bandwidth settings can cause EIGRP to use too much or too little bandwidth, degrading performance.

EIGRP uses the DUAL algorithm for calculating the best paths. Routes are identified by the letter D, which stands for DUAL.