EIGRP Route Metric Calculation | Cisco Exam 200-301

# How EIGRP Determines Route Metric

### Question

By default, how does EIGRP determine the metric of a route for the routing table?

### Explanations

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EIGRP (Enhanced Interior Gateway Routing Protocol) is a Cisco proprietary routing protocol that is used for routing within an autonomous system (AS). EIGRP determines the best path to a destination network based on a metric that is calculated using several factors. By default, EIGRP uses the bandwidth and delay values of the path to calculate the route metric.

EIGRP considers the following factors to calculate the metric of a route:

1. Bandwidth: The available bandwidth on the path between the source and destination routers is a major factor in determining the metric. EIGRP uses the bandwidth value of the lowest bandwidth link along the path to calculate the metric.

2. Delay: The delay of the path between the source and destination routers is another important factor in determining the metric. EIGRP uses the cumulative delay of all links along the path to calculate the metric.

3. Reliability: The reliability of the links along the path is also taken into account by EIGRP when calculating the metric. The more reliable the links, the lower the metric.

4. Load: The current load on the links along the path is also considered by EIGRP. If a link is heavily loaded, EIGRP will assign a higher metric to that path.

By default, EIGRP uses the bandwidth and delay values of the path to calculate the route metric. The formula used to calculate the metric is:

metric = [(k1 * bandwidth) + (k2 * bandwidth / (256 - load)) + (k3 * delay)]

where k1, k2, and k3 are constants that are used to weight the importance of the factors. By default, k1 = 1, k2 = 0, and k3 = 1. The bandwidth value is the bandwidth of the lowest bandwidth link along the path. The delay value is the cumulative delay of all links along the path.

In summary, EIGRP calculates the metric of a route based on several factors, including the bandwidth, delay, reliability, and load of the links along the path. By default, EIGRP uses the bandwidth and delay values of the path to calculate the route metric using a formula that assigns weights to the different factors.