eigrp的基本原理及執行個體

?EIGRP is an advanced distance vector routing protocol

–Automatically establishes neighbor relationships with peer devices

–Relies on IP packets for delivery of routing information

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1.EIGRP 特征

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2.DUAL 算法

*選擇最小代價，無環路的路徑到每個目的網絡

*AD=下一跳路由器到達目的網絡的cost值

*FD=AD+本路由器到下一跳路由器的cost值

*Lowest-cost = lowest FD

*(Current) successor = 擁有Lowest-cost的路徑及下一跳路由

*Feasible successor =無環路的備份路由器 (該路徑的AD必須比目前的successor的FD小)

*鄰居之間互相通告路由

*選擇successor放入資料庫中，同時把feasible successors也放入資料庫中

*如果successor丢失了，使用feasible successor

*如果沒有feasible successor，則向鄰居查詢并重新計算新的successor

3.三張表格：

EIGRP IP路由表

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4.封包格式：

*Hello: 維持鄰居關系.

*Update: 發送路由更新.

*Query: 向鄰居查詢路由資訊.

*Reply: 相應路由器的查詢.

*ACK: 對EIGRP可靠包的确認.

5.初始路由發現

6.預設路由方法：

*重分布靜态

*R(config)#ip route 0.0.0.0 0.0.0.0 s0

*R(config-router)#redistribute static

*宣告0.0.0.0

*R(config-router)#network 0.0.0.0

*配置預設網絡

*R(config)#ip default-network 10.0.0.0

*R(config-router)#network 10.0.0.0

*R(config)#ip route 10.0.0.0 255.0.0.0 null0

7.等代價負載均衡

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?Router E chooses router C to get to network Z, because it has lowest FD of 20.

?With a variance of 2, router E chooses router B to get to network Z (20 + 10 = 30) &lt; [2 * (FD) = 40].

?Router D is never considered to get to network Z (because 25 &gt; 20).

8.支援的網絡 vlsm

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?EIGRP supports

–Multiaccess (LANs)

–Point-to-point (HDLC)

–NBMA (Frame Relay)

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9.多點傳播位址 224.0.0.10  hello包每5秒發送一次（在高速鍊路上）

?Two routers become neighbors when they see each other’s hello packet

–Hello address = 224.0.0.10

?Hellos sent once every 5 seconds on the following links:

–Broadcast media: Ethernet, Token Ring, FDDI

–Point-to-point serial links: PPP, HDLC, 

point-to-point Frame Relay/ATM subinterfaces

–Multipoint circuits with bandwidth greater than T1: ISDN PRI, SMDS, Frame Relay

?Hellos sent once every 60 seconds on the following links:

–Multipoint circuits with bandwidth less than T1: ISDN BRI, Frame Relay, SMDS, and so on

?Neighbor declared dead when no EIGRP packets are received within hold interval

–Not only hello can reset the hold timer

?Hold time by default is three times the hello time  保持時間 是3倍的HELLO時間

本文轉自 gjp0731 51CTO部落格，原文連結:http://blog.51cto.com/guojiping/956931