Cisco's Enhanced Interior Gateway Routing Protocol (EIGRP)
RFC 7868

Document Type RFC - Informational (May 2016; No errata)
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Last updated 2016-05-25
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Independent Submission                                         D. Savage
Request for Comments: 7868                                         J. Ng
Category: Informational                                         S. Moore
ISSN: 2070-1721                                            Cisco Systems
                                                                D. Slice
                                                        Cumulus Networks
                                                               P. Paluch
                                                    University of Zilina
                                                                R. White
                                                                LinkedIn
                                                                May 2016

       Cisco's Enhanced Interior Gateway Routing Protocol (EIGRP)

Abstract

   This document describes the protocol design and architecture for
   Enhanced Interior Gateway Routing Protocol (EIGRP).  EIGRP is a
   routing protocol based on Distance Vector technology.  The specific
   algorithm used is called "DUAL", a Diffusing Update Algorithm as
   referenced in "Loop-Free Routing Using Diffusing Computations"
   (Garcia-Luna-Aceves 1993).  The algorithm and procedures were
   researched, developed, and simulated by SRI International.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This is a contribution to the RFC Series, independently of any other
   RFC stream.  The RFC Editor has chosen to publish this document at
   its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7868.

Savage, et al.                Informational                     [Page 1]
RFC 7868                      Cisco's EIGRP                     May 2016

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

   This document may not be modified, and derivative works of it may not
   be created, except to format it for publication as an RFC or to
   translate it into languages other than English.

Table of Contents

   1. Introduction ....................................................5
   2. Conventions .....................................................5
      2.1. Requirements Language ......................................5
      2.2. Terminology ................................................5
   3. The Diffusing Update Algorithm (DUAL) ...........................9
      3.1. Algorithm Description ......................................9
      3.2. Route States ..............................................10
      3.3. Feasibility Condition .....................................11
      3.4. DUAL Message Types ........................................13
      3.5. DUAL Finite State Machine (FSM) ...........................13
      3.6. DUAL Operation -- Example Topology ........................18
   4. EIGRP Packets ..................................................20
      4.1. UPDATE Packets ............................................21
      4.2. QUERY Packets .............................................21
      4.3. REPLY Packets .............................................22
      4.4. Exception Handling ........................................22
           4.4.1. Active Duration (SIA) ..............................22
                  4.4.1.1. SIA-QUERY .................................23
                  4.4.1.2. SIA-REPLY .................................24
   5. EIGRP Operation ................................................25
      5.1. Finite State Machine ......................................25
      5.2. Reliable Transport Protocol ...............................25
           5.2.1. Bandwidth on Low-Speed Links .......................32
      5.3. Neighbor Discovery/Recovery ...............................32
           5.3.1. Neighbor Hold Time .................................32
           5.3.2. HELLO Packets ......................................33
           5.3.3. UPDATE Packets .....................................33
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