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Chapter 9 - EIGRP CCNA Exploration 4.0 1 Objectives • • • • • Describe the background and history of Enhanced Interior Gateway Routing Protocol (EIGRP). Examine the basic EIGRP configuration commands and identify their purposes. Calculate the composite metric used by EIGRP. Describe the concepts and operation of DUAL. Describe the uses of additional configuration commands in EIGRP. Học viện mạng Bach Khoa - Website: www.bkacad.com 2 Introduction Học viện mạng Bach Khoa - Website: www.bkacad.com 3 Introduction to EIGRP Học viện mạng Bach Khoa - Website: www.bkacad.com 4 EIGRP • Roots of EIGRP: IGRP – Developed in 1985 to overcome RIPv1’s limited hop count – Distance vector routing protocol – Metrics used by IGRP  Bandwidth (used by default).  Delay (used by default).  Reliability.  Load. – Discontinued support starting with IOS 12.2(13)T & 12.2(R1s4)S. Học viện mạng Bach Khoa - Website: www.bkacad.com 5 Traditional Distance Vector Routing Protocols • Use the Bellman-Ford or Ford-Fulkerson algorithm. • Age out routing entries and uses periodic updates. • Keep track of only the best routes; the best path to a destination network. • When a route becomes unavailable, the router must wait for a new routing update. • Slower convergence due to holddown timers. Enhanced Distance Vector Routing Protocol: EIGRP • Uses the Diffusing Update Algorithm (DUAL) • Does not age out routing entries nor uses periodic updates. • Maintains a topology table separate from the routing table, which includes the best path and any loopfree backup paths. • When a route becomes unavailable, DUAL will use a backup path if one exists in the topology table. • Faster convergence due to the absence of holddown timers and a system of coordinated route calculations. Học viện mạng Bach Khoa - Website: www.bkacad.com 6 EIGRP Message Format • EIGRP Header Học viện mạng Bach Khoa - Website: www.bkacad.com 7 EIGRP • • EIGRP packet header contains: – Opcode field – Autonomous System number(AS). EIGRP Parameters contains: – Weights. – Hold time. Học viện mạng Bach Khoa - Website: www.bkacad.com 8 EIGRP • TLV: IP internal contains – Metric field. – Subnet mask field. – Destination field. • TLV: IP external contains – Fields used when external. – Routes are imported into EIGRP routing process. Học viện mạng Bach Khoa - Website: www.bkacad.com 9 EIGRP Học viện mạng Bach Khoa - Website: www.bkacad.com 10