CCNP Advance EIGRP Features

Route summarization
EIGRP has the ability to auto summarize networks. However, if the networks are limited, you may want to disable automatic summarization. In order to do this enter the following command:
Router(config) # no auto-summary.
The limitation with auto summarization is that EIGRP is only capable of summarizing networks which are part of the network. Therefore, for these cases you have to input an auto summarization which the following command:

ip summary-address eigrp 100
subnet

Load balancing in Equal Cost Path

In an equal cost path, the links in the network have are symmetric which means they use the same circuit type and the same same bandwidth capacity, so the same cost is assigned to the each link.
Since both link have the same distance as well, the metrics for its destination is available, through these links which are equal. When EIGRP chooses the successor route, it wants to choose a link which is at the lowest cost. When it sees that the 2 path ways have the same metric then it chooses them as its successors. After this EIGRP will then be able to share the traffic loads across the multiple links, which is known as load balancing.

Load Balancing in Unequal Cost Path
Unequal cost load balancing is when traffic across multiple routes is balanced withing different metric routes. This load balance is done through the variance command.

Router(config-router) #
variance multiplier
In load balancing, the multiplier parameter the values from 1-128 are used. 1 is the default value where there is an equal cost for load balancing


Suppose we have a network with 3 path way
Path 1 has a metric of 10
Path 2 has a metric of 15
Path 3 has a metric of 30
The path which will be selected will be the first path since the metric is lowest in path 1. With EIGRP you have to select that path, and configure it with a variance of 2.
Once you multiply by path and variance then you will get a minimum variance of 20.
10 metric * 2 variance value = 20 minimum metric
EIGRP will includes all routes that have a metric of less than 20 and satisfy the workable condition. EIGRP will take both path one and two since their metric distance is less than 20. The 3rd path will not be taken since 20< 25.
Therefore, the load balancing will occur between path one and path two.
Bandwidth Utilization

Bandwidth needs to saved within networks, so the network performance can be enhanced. By default EIGRP is set to use up to 50 % of bandwidth within an interface for routing traffic. However, this can be changed by using the following command:
ip bandwidth-percent eigrp as-number percentage the as number is AS number and percent is percentage you want to input.

When configuring multipoint interfacess such as Frame Relay it is important to to set the bandwidth to equal to share it across the neighbors.