Chapter 9. EIGRP

CCNA Exploration 2.

Routing protocols and Consepts.

RESUME. Chapter 9.  EIGRP

      Enhanced Interior Gateway Routing Protocol (EIGRP) is a distance vector, classless routing protocol that was released in 1992 with IOS 9.21.

      EIGRP includes several features that are not commonly found in other distance vector routing protocols like RIP (RIPv1 and RIPv2) and IGRP. 

These features include:

              ~  Reliable Transport Protocol (RTP)

              ~  Bounded Updates

              ~  Diffusing Update Algorithm (DUAL)

              ~  Establishing Adjacencies

              ~  Neighbor and Topology Tables

The destination address is set to the multicast 224.0.0.10. If the EIGRP packet is encapsulated in an Ethernet frame, the destination MAC address is also a multicast address.

          The Autonomous System (AS) Number specifies the EIGRP routing process.

     The EIGRP parameters message includes the weights that EIGRP uses for its composite metric. By default, only bandwidth and delay are weighted. Both are equally weighted, therefore, the K1 field for bandwidth and the K3 field for delay are both set to 1. The other K values are set to zero. 

        EIGRP has the capability for routing several different protocols including IP, IPX, and AppleTalk using protocol-dependent modules (PDM). PDMs are responsible for the specific routing tasks for each Network layer protocol. 

        Reliable Transport Protocol (RTP) is the protocol used by EIGRP for the delivery and reception of EIGRP packets. EIGRP was designed as a Network layer independent routing protocol; therefore, it cannot use the services of UDP or TCP because IPX and Appletalk do not use protocols from the TCP/IP protocol suite. 

                        

        EIGRP Packet Types

• Hello packets are used by EIGRP to discover neighbors and to form adjacencies with those neighbors. EIGRP hello packets are multicasts and use unreliable delivery. EIGRP Hello packets are discussed in a later section.
• Update packets are used by EIGRP to propagate routing information. Update packets are sent only when necessary. EIGRP updates contain only the routing information needed and are sent only to those routers that require it. 
• Acknowledgement (ACK) packets are sent by EIGRP when reliable delivery is used. RTP uses reliable delivery for EIGRP update, query, and reply packets. EIGRP acknowledgement packets contain a nonzero acknowledgment number and always are sent by using a unicast address.
• Query and reply packets are used by DUAL when searching for networks and other tasks. Queries and replies use reliable delivery. Queries use multicast, whereas replies are always sent as unicast. 

EIGRP uses the term partial or bounded when referring to its update packets. 

The term partial means that the update only includes information about the route changes. EIGRP sends these incremental updates when the state of a destination changes, instead of sending the entire contents of the routing table. 

The term bounded refers to the propagation of partial updates sent only to those routers that are affected by the change. The partial update is automatically "bounded" so that only those routers that need the information are updated. 

Diffusing Update Algorithm (DUAL) is the convergence algorithm used by EIGRP instead of the Bellman-Ford or Ford Fulkerson algorithms used by other distance vector routing protocols, like RIP. 

Like other routing protocols, EIGRP can be configured for authentication. RIPv2, EIGRP, OSPF, IS-IS, and BGP can all be configured to encrypt and authenticate their routing information.

Note: Authentication does not encrypt the router's routing table.

An autonomous system (AS) is a collection of networks under the administrative control of a single entity that presents a common routing policy to the Internet. 

Router(config)#router eigrp autonomous-system

The network command in EIGRP has the same function as in other IGP routing protocols: 

1. Any interface on this router that matches the network address in the network command will be enabled to send and receive EIGRP updates.

2. This network (or subnet) will be included in EIGRP routing updates.

Router(config-router)#network network-address

To configure EIGRP to advertise specific subnets only, use the wildcard-mask option with the network command:

Router(config-router)#network network-address [wildcard-mask] 

To calculate the inverse of the subnet mask, subtract the subnet mask from 255.255.255.255:

  255.255.255.255 

- 255.255.255.252

Subtract the subnet mask

---------------

    0.  0.  0.  3  - Wildcard mask

Use the show ip eigrp neighbors command to view the neighbor table and verify that EIGRP has established an adjacency with its neighbors. 

Note: EIGRP automatically includes a null0 summary route as a child route whenever both of following conditions exist:

----There is at least one subnet that was learned via EIGRP.

----Automatic summarization is enabled.

EIGRP uses the following values in its composite metric to calculate the preferred path to a network:

 Router(config-router)#metric weights tos k1 k2 k3 k4 k5

• Bandwidth                                                                                                Modifying the bandwidth value does not change the actual bandwidth of the link.       Router(config-if)#bandwidth kilobits
• Delay
• Reliability                                                                                                          By default, EIGRP does not use reliability in its metric calculation.
• Load                                                                                                                Load (load) reflects the amount of traffic utilizing the link.

A successor is a neighboring router that is used for packet forwarding and is the least-cost route to the destination network. 

Feasible distance (FD) is the lowest calculated metric to reach the destination network. 

A feasible successor (FS) is a neighbor who has a loop-free backup path to the same network as the successor by satisfying the feasibility condition.

 The feasibility condition (FC) is met when a neighbor's reported distance (RD) to a network is less than the local router's feasible distance to the same destination network.

The show ip eigrp topology all-links command shows all possible paths to a network including successors, feasible successors, and even those routes that are not feasible successors. 

Задаем № Autonomous System.На всех Rx AuSys он должен быть одинаковый.
теперь необходимо объявить непосредственно подключенные сети.
R1(config)# router eigrp 1
Включение EIGRP на интерфейсах:
R1(config-router)# network <network> [wildcard mask]
<network> — непосредственно присоединенная сеть к маршрутизатору.
Если в route table есть default static route, то можно его распространить :
R1(config-router)# redistribute static [metric]
Маршрут по умолчанию EIGRP:
R1(config)# ip default-network <network-number>
Отключить автосуммирование:R1(config-router)#no auto-summary
Суммарный маршрут настраивается на интерфейсе:
R1(config-if)#ip summary-address eigrp <AS-number> <address> <mask> [admin-distance]
Изменения интервала hello-пакетов:
router(config-if)# ip hello-interval eigrp <asn> <seconds>
Изменения hold-интервала:
router(config-if)# ip hold-time eigrp <asn> <seconds>
R1(config-if)# bandwith (Kbps)Настройка % bandwidth, к-й будет исп-вать EIGRP:
R1(config-if)#ip bandwidth-percent eigrp <AS-number> <percent>

TROUBLESHOOTING
R1#sh ip eigrp neighbors:
R1#sh ip eigrp neighbors detail
R1# sh ip route eigrp
R1#sh ip protocols
R1#sh ip eigrp interfaces
R1#sh ip eigrp topology
R1# debug ip eigrp