A properly designed EIGRPv6 domain is easy to configure, converges quickly and if there is a change in the topology it can rapidly re-converge.

This lesson provides a brief summary of some of the basic concepts EIGRPv6. The purpose is to provide a high-level overview. Many of the topics introduced here will be described in more detail in future lessons.

A Brief History

Before EIGRP there was IGP (Interior Gateway Protocol). As networks became more complex, IGP was “enhanced”. Hence the name, Enhanced Interior Gateway Routing Protocol. EIGRP is backwards comparable with IGP.

EIGRP was created by Cisco in 1992 and the full version is proprietary.

In 2016, Cisco made a version with basic functionality available as an open standard to the IETF with RFC 7868. If you want to use EIGRP on a non-Cisco device, be careful that the version of EIGRP available for that device has the features you need.

EIGRP for IPv6 (EIGRPv6) was released in 2017 with RFC 8200.

Overview

Enhanced Interior Gateway Routing Protocol version 6 (EIGRPv6) is an Advanced Distance Vector routing protocol for IPv6 only. Distance Vector Protocols are concerned with “how far” (Distance) a destination is and which direction the next-hop is (Vector). EIGRP is an Advanced Distance Vector Protocol because it has additional features that make it superior to other Distance Vector protocols like RIPng.

EIGRP has a very low demand on network resources such as bandwidth and CPU, especially when compared to Link-State protocols..

One reason for this is that EIGRP will only send full topology information to its EIGRP Neighbors only when the neighborship is initially formed. After that, it will only send partial routing updates to notify neighbors about a change in the topology if a change occurs.

Link-State Protocols like OSPF send full topology information at regular intervals. Because of this, OSPF sends more information more often. CPUs also need to work more to process the additional data on both the sending and receiving devices.

FYI: More reasons for EIGRP's benefits will present themselves in this lesson and future lessons.

EIGRP for IPv4 and IPv6

EIGRP can be run for IPv4 only, IPv6 only and Dual Stack (IPv4 and IPv6 together).

Configuration of Dual Stack is simplified by using the Address Families feature that is available in EIGRP’s Named Mode. Even though IPv4 and IPv6 can both be configured under the same Named Mode router process, they work completely independent of each other.

  • They use separate topology tables.
  • They use separate routing tables.
  • IPv4 routes can only be communicated via IPv4 and IPv6 routes can only be communicated via IPv6. (This is different than OSPFv3 that can advertise IPv4 over IPv6.)

Distance Vector and EIGRP

Distance Vector protocols are much faster than Link-state protocols.

One reason for this is because Distance Vector protocols only need to know “how far” and the next-hop for a destination. Link-state protocols, for example, require devices to re-calculate the entire topology because each device needs to choose routes from its own "map" of the entire routing protocol's domain.

Distance

Distance refers to the metric used to determine the cost to a destination.

There are two types of Distance:

  1. Reported Distance - The metric for a route advertised by the next hop neighbor(s). (The Reported Distance is also sometimes called the Advertised Distance.)

Reported Distance Topology
Reported Distance

In the above example, the Distance is measured from the source router's next-hop to the destination network.

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