Dynamic routing protocols: EIGRP
EIGRP-- enhanced interior gateway protocol for enhanced IGRP is a distance vector protocol, directly above the work on the IP layer protocol number is 88. Cisco proprietary protocol.
EIGRP features:
① is an advanced distance-vector protocol . Advanced reflected in the algorithm of its operation, run DUAL algorithm, along with some of the features that EIGRP distance vector protocol and the link-state protocols.
② Fast Convergence:
Convergence: equipment arrived during normal operation (start forwarding data packets) from the boot or from the network to process changes back to normal. So fast convergence refers to a device to restore the normal operation of a short time.
③100% loop-free
but also because the algorithm of its operation
④ incremental update.
Will be updated for a certain change of entry.
⑤ the only one to support both load balancing and equivalence agreement not equivalent load balancing.
A. cost load balancing: In the case of the same metric, the router sends the data packets in the same way each one.
By default, EIGRP is equivalent load balance
By default, the routing table with at most equal to the minimum metric four metric route, this value can be changed to change at most 16. A
IOU3 (config-Router) maximum-Paths # 10
B. Non-cost load balancing: the metric values in different situations, based on proportional routing metric, the transmission ratio of the corresponding data packet.
Default value is 1 V, for equivalent load balance
Implemented without the equivalent load balancing :
. A presence FS, FD optimal path is greater than AD-- suboptimal paths meet the FC
B × V value of the FD optimal path> FD suboptimal path.
⑥通过组播和单播来代替广播。
组播地址：224.0.0.10
单播：
⑦支持VLSM。
证明是一个无类路由协议
⑧可以在网络中的任意一个节点进行手动汇总。
eigrp本质上是一个距离矢量协议，默认情况下是开启自动汇总，会在边界上将明细的路由汇总成一个主类的网段，但是一般情况我们倾向于手动汇总。
手动汇总：出接口
IOU1(config-if)#ip summary-address eigrp 90 172.16.0.0 255.255.0.0
三张表
①邻居表：启用了eigrp协议的路由器就会自动往组播地址224.0.0.10发送hello包（5s 15s），同时也会接收到其他eigro路由器的hello包，此时就会建立了邻居，把对方的IP地址和和hello包的接收接口存放进邻居表。所以eigrp的邻居表存放的就是对方IP地址和接受接口的关联信息。
IOU3#show ip eigrp neighbors
注意：eigrp本质上是一个距离矢量协议，默认只能知道直连的接口情况，所以在每台路由器的邻居表中看到的邻居地址一定是跟自己相连的那个接口地址。
*②拓扑表：建立邻居之后，邻居之间就会相互通告彼此的路由网段，然后将这些网段汇总起来形成一张拓扑表，所以eigrp的拓扑表存放的就是到达各个目的地的路由信息。**
IOU1#show ip eigrp topology
③路由表：在拓扑表中选择一条最优路径添加到路由表。
IOU1#show ip route eigrp
eigrp如何衡量一条路径是否最优---通过DUAL算法
DUAL算法：拓展更新算法--用于计算eigrp的最优无环路径以及备份路径
DUAL算法的几个参数：
S--继任者--后继路由器：最优路径对应的邻居路由器
FS--可行性继任者：满足一定条件的路由器（次优）
FC--可行性条件：满足FC，必须满足次优路径的AD小于最优路径的FD
FD--可行性距离：到达目的地的度量值。
AD--通告距离：下一跳到达目的地的度量值。
EIGRP度量值的计算：与K值有关
K1：带宽 K2：负载 K3：延迟 K4：可靠性 K5：MTU
默认情况下：K1=1 K2=0 K3=1 K4=0 K5=0
所以默认的度量值计算=带宽+延迟
带宽=（10^7/前往目标所有出站接口中的最小带宽）×256
延迟=（前往目标所有出站接口的延迟累积和/10μs）×256
EIGRP Basic configuration:
IOU1 (config) #router eigrp 90 - created eigrp routing process, as is No. 90 (AS No. The two sides must be consistent, otherwise it is impossible to establish the neighbor)
IOU1 (config-Router) Auto-#no the Summary - Close automatically aggregated
IOU1 (config-router) #network 192.168.12.0 0.0.0.255-- advertisement segment, back to keep the wildcard
IOU1 (config-router) #network 12.12.12.0 - if not kept pace with the reverse mask, The default notice is the main class segment
pick√