Enhanced Interior Gateway Routing Protocol

The Enhanced Interior Gateway Routing Protocol ( EIGRP ) is a 1992 book published by Cisco proprietary routing protocol. Cisco announced in March 2013 to make it the open standard. When EIGRP is an enhanced version of IGRP earlier, at which persists compatibility.

EIGRP is an advanced distance-vector routing protocol, which behaves in the exchange with nearby devices as well as in the storage of routing information, such as a link-state routing protocol. Due to the extensive features which are more likely to be found at link-state protocols, EIGRP is therefore often classified as a balanced hybrid routing protocol. With the help of those link-state properties EIGRP achieved relative to conventional distance-vector routing protocols, a very rapid convergence and is immune to routing loops. The fast convergence and above all, reliability in environments with dynamically cross-linked by NHRP GRE tunnels allow EIGRP appear as an interesting alternative to OSPF.

Function

In EIGRP neighboring routers in a neighbor table ( neighbor table ) are stored. All routes, which will be announced on these neighbors are again collected in a Topology Table ( topology table). The best route to a destination network is determined in EIGRP with the Diffusing Update Algorithm ( DUAL).

The calculation of the metrics for different routes based on EIGRP to the same procedure as in IGRP, due to the extended field for storing the metric scale EIGRP However, compared with IGRP, the value by a factor of 256 In the manual conversion of values ​​between EIGRP and IGRP routers must take this into account, in practice, the conversion is automatic.

As an improvement over the method IGRP Classless Inter- Domain Routing (CIDR ) and Variable Length Subnet Mask ( VLSM ) are supported. Since these features are now standard in modern networks, IGRP plays no significant role more in practice.

Multi-protocol properties

Primary support EIGRP the Internet Protocol ( IP), IPX, and AppleTalk protocols to be routed to the third layer of the OSI reference model. Due to its modular design, it is possible with the help of so-called Protocol -dependent modules (PDM ) to use newer protocols such as IPv6 having to update itself without EIGRP.

A router, which operates to EIGRP, manages for each protocol of the OSI layer 3, a separate routing table, a neighbor table and a topology table.

However, the multi-protocol characteristics of EIGRP in the current versions of IOS are no longer fully supported. Thus, only IP and IPX remain as to be routed protocols.