EIGRP水平分割
1.1.1.所需設備
下面是做這個實驗練習所需的設備：
1) 三臺具有一個串行端口的Cisco路由器；
2) Cisco IOS 10.0版或更高；
3) 一臺運行了終端仿真程序的PC；
4) 三根Cisco DTE/DCE交叉電纜；
5) 一根Cisco扁平電纜供路由器的控制檯端口訪問使用。
配置概述
驗證EIGRP在Hub-Spoke拓撲結構下水平分割對其影響及解決方式，具體實驗要求：R1、R2、R3三臺路由器通過幀中繼網絡連接，拓撲類型爲 Hub-Spok模型。R1爲Hub，R2、R3爲Spoke路由器，三臺路由器之間運行EIGRP協議，通過配置EIGRP水平分割特性，始三臺路由器路由表學習完整，即三臺路由器均通過EIGRP學習到2條路由
3.路由器配置
1. 幀交換機
FrameSwitch# show running-config
!
hostname FrameSwitch
!
frame-relay switching
!
interface Serial0/1
encapsulation frame-relay
frame-relayintf-type dce
frame-relayroute 102 interface Serial0/2 201
!
interface Serial0/2
encapsulation frame-relay
frame-relayintf-type dce
frame-relayroute 201 interface Serial0/1 102
frame-relayroute 203 interface Serial0/3 302
!
interface Serial0/3
encapsulation frame-relay
frame-relay intf-type dce
frame-relayroute 302 interface Serial0/2 203
!
end
2. 路由器R1
R1#show running-config
interface Loopback0
ip address 1.1.1.1255.255.255.0
!
interface Serial0/1
ip address 123.123.123.1255.255.255.0
encapsulation frame-relay
frame-relaymap ip 123.123.123.3 102 broadcast
frame-relaymap ip 123.123.123.2 102 broadcast
!
router EIGRP 90
network 1.0.0.0
network 123.123.123.0
auto-summary
!
!
end
3. 路由器R2
R2#show running-config
!
interface Loopback0
ip address 2.2.2.2255.255.255.0
!
interface Serial0/2
ip address 123.123.123.2255.255.255.0
encapsulation frame-relay
frame-relaymap ip 123.123.123.3 203 broadcast
frame-relaymap ip 123.123.123.1 201 broadcast
!
router EIGRP 90
network 2.0.0.0
network 123.123.123.0
auto-summary
!
!
end
4. 路由器R3
R3#showrunning-config
!
interface Loopback0
ip address 3.3.3.3255.255.255.0
!
interface Serial0/3
ip address 123.123.123.3255.255.255.0
encapsulation frame-relay
frame-relaymap ip 123.123.123.2 301 broadcast
frame-relaymap ip 123.123.123.1 301 broadcast
!
router EIGRP 90
network 3.0.0.0
network 123.123.123.0
auto-summary
!
!
end
4.監測配置
查看EIGRP鄰居
R1
R1#show ip eigrp neighbors
IP-EIGRP neighbors for process 90
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 123.123.123.2 Se0/1 178 00:03:40 1311 5000 0 7
R2
R2#show ip eigrp neighbors
IP-EIGRP neighbors for process 90
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
1 123.123.123.1 Se0/2 158 00:05:45 176 1584 0 3
0 123.123.123.3 Se0/2 154 00:06:00 158 948 0 3
R3
R3#show ip eigrp neighbors
IP-EIGRP neighbors for process 90
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 123.123.123.2 Se0/3 158 00:06:58 170 1020 0 7
查看路由表
R1
Gateway of last resort is not set
Gateway of last resort is not set
1.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 1.1.1.0/24is directly connected, Loopback0
D 1.0.0.0/8is a summary, 00:07:05, Null0
D 2.0.0.0/8[90/2297856] via 123.123.123.2, 00:07:03, Serial0/1
123.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 123.123.123.0/24 is directly connected, Serial0/1
D 123.0.0.0/8 is a summary, 00:07:05, Null0
R1 路由表不正常，不能夠正常學習到R3 環回接口的路由條目
R2
R2#show ip route
Gateway of last resort is not set
D 1.0.0.0/8[90/2297856] via 123.123.123.1, 00:08:55, Serial0/2
2.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 2.2.2.0/24is directly connected, Loopback0
D 2.0.0.0/8is a summary, 00:09:12, Null0
D 3.0.0.0/8[90/2297856] via 123.123.123.3, 00:09:12, Serial0/2
123.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 123.123.123.0/24 is directly connected, Serial0/2
D 123.0.0.0/8 is a summary, 00:09:12, Null0
R2的路由表正常，學到R1、R3的環回接口路由
R3
R3#show ip route
Gateway of last resort is not set
D 2.0.0.0/8[90/2297856] via 123.123.123.2, 00:09:38, Serial0/3
3.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 3.3.3.0/24is directly connected, Loopback0
D 3.0.0.0/8is a summary, 00:09:54, Null0
123.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 123.123.123.0/24 is directly connected, Serial0/3
D 123.0.0.0/8 is a summary, 00:09:54, Null0
同樣，R3無法學到R1的路由
在這裏，因爲幀中繼網絡是一個NBMA網絡，R2通過相同的物理接口s0/2接口與R1、R３通信，由於EIGRP 是一個距離矢量型協議，具有水平分割特性，所以水平分割抑制了R1、R3 之間的路由學習（R1、R3 之間的路由學習需要通過R2轉發，但由於水平分割特性，R2從s0/1接口學習到的路由不會再從相同接口轉發出去）。
解決方法
方法一：關閉R2路由器s0/2接口的水平分割
配置如下：
R2(config)#int s0/2
R2(config-if)#no ip split-horizon eigrp 90
//注意，這裏跟RIP下關閉水平分割不同，命令後面必須跟上eigrp及AS號。
再查看R1、R3的路由表
R1#show ip route
Gateway of last resort is not set
1.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 1.1.1.0/24is directly connected, Loopback0
D 1.0.0.0/8is a summary, 00:00:09, Null0
D 2.0.0.0/8[90/2297856] via 123.123.123.2, 00:12:17, Serial0/1
D 3.0.0.0/8[90/2809856] via 123.123.123.2, 00:00:09, Serial0/1
123.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 123.123.123.0/24 is directly connected, Serial0/1
D 123.0.0.0/8 is a summary, 00:12:19, Null0
R3#show ip route
Gateway of last resort is not set
D 1.0.0.0/8[90/2809856] via 123.123.123.2, 00:00:41, Serial0/3
D 2.0.0.0/8[90/2297856] via 123.123.123.2, 00:13:06, Serial0/3
3.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 3.3.3.0/24is directly connected, Loopback0
D 3.0.0.0/8is a summary, 00:00:41, Null0
123.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 123.123.123.0/24 is directly connected, Serial0/3
D 123.0.0.0/8 is a summary, 00:13:22, Null0
可以看到R1、R3 已經正常學習到對方的路由信息了
方法二：將單一物理接口劃分爲兩個子接口
使用幀中繼子接口，將原本的單一物理接口劃分爲兩個子接口，水平分割便不會影響路由器間的路由轉發了，但是啓用子接口之後會需要另一個子網（幀中繼每個子接口都是一個獨立子網）：
圖-- 幀中繼子接口
R2需要將s0/2接口配置爲幀中繼子接口，分爲兩個網段。
R2：
interface Serial0/2
no ipaddress
encapsulation frame-relay
serialrestart-delay 0
!
interface Serial0/2.1 point-to-point
ip address123.1.1.2 255.255.255.0
frame-relayinterface-dlci 201
!
interface Serial0/2.2 point-to-point
ip address123.1.2.2 255.255.255.0
frame-relayinterface-dlci 203
!
R1：
interface Serial0/1
ip address123.1.1.1 255.255.255.0
encapsulation frame-relay
serialrestart-delay 0
frame-relay map ip 123.1.1.2 102 broadcast
noframe-relay inverse-arp
!
R3：
interface Serial0/3
ip address123.1.2.3 255.255.255.0 //與前例不同，這裏R3在另一個子網內，對應R2子接口s0/2.2。
encapsulation frame-relay
serialrestart-delay 0
frame-relaymap ip 123.1.2.2 302 broadcast
配置EIGRP：
R1：
router eigrp 90
network 1.1.1.00.0.0.255
network 123.1.1.0 0.0.0.255
noauto-summary
R2：
router eigrp 90
network 2.2.2.0 0.0.0.255
network 123.1.1.0 0.0.0.255
network 123.1.2.0 0.0.0.255
no auto-summary
R3：
routereigrp 90
network 3.3.3.00.0.0.255
network 123.1.2.0 0.0.0.255
no auto-summary
現在查看路由表
R1
R1#show ip rou
Gateway of last resort is not set
1.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 1.1.1.0/24is directly connected, Loopback0
D 1.0.0.0/8is a summary, 00:31:52, Null0
D 2.0.0.0/8[90/2297856] via 123.1.1.2, 00:09:28, Serial0/1
D 3.0.0.0/8[90/2809856] via 123.1.1.2, 00:03:33, Serial0/1
123.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
D 123.1.2.0/24 [90/2681856] via 123.1.1.2, 00:09:28, Serial0/1
C 123.1.1.0/24 is directly connected, Serial0/1
D 123.0.0.0/8 is a summary, 00:31:52, Null0
R2
R2#show ip rou
Gateway of last resort is not set
D 1.0.0.0/8[90/2297856] via 123.1.1.1, 00:10:10, Serial0/2.1
2.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 2.2.2.0/24is directly connected, Loopback0
D 2.0.0.0/8is a summary, 00:33:07, Null0
D 3.0.0.0/8[90/2297856] via 123.1.2.3, 00:04:16, Serial0/2.2
123.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 123.1.2.0/24 is directly connected, Serial0/2.2
C 123.1.1.0/24 is directly connected,Serial0/2.1
D 123.0.0.0/8 is a summary, 00:33:06, Null0
R3
R3#show ip rou
Gateway of last resort is not set
D 1.0.0.0/8[90/2809856] via 123.1.2.2, 00:04:39, Serial0/3
D 2.0.0.0/8[90/2297856] via 123.1.2.2, 00:04:39, Serial0/3
3.0.0.0/8is variably subnetted, 2 subnets, 2 masks
C 3.3.3.0/24is directly connected, Loopback0
D 3.0.0.0/8is a summary, 00:54:07, Null0
123.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 123.1.2.0/24 is directly connected, Serial0/3
D 123.1.1.0/24 [90/2681856] via 123.1.2.2, 00:04:39, Serial0/3
D 123.0.0.0/8 is a summary, 00:06:34, Null0
在幀中繼Hub-and-Spoken 拓撲結構中，默認水平分割開啓的情況下，只有Hub路由器能夠學習到完整的路由，由於水平分割作用，兩個Spoke路由器均不能學習到對方的路由信息，解決方法是將Hub路由器接口的水平分割關閉，或者使用幀中繼子接口來解決這個問題。