CCNP路由实验---3、人工汇总EIGRP路由

实验目的：

1、理解EIGRP的自动汇总的缺点。

2、掌握EIGRP的手工自动总结的配置方法。

实验拓扑：

 

实验步骤：

1、配置各路由器的名称、相连接口IP地址，并且使用Ping命令确认各路由器的直连口的互通性。 

R1：

R1(config)#int s1/1

R1(config-if)#ip add 172.16.1.1 255.255.255.252

R1(config-if)#no shut

R2：

R2(config)#  int s1/0

R2(config-if)#ip add 172.16.1.2 255.255.255.252

R2(config-if)#no shut

R2(config)#int s1/1

R2(config-if)#ip add 172.16.1.5 255.255.255.252

R2(config-if)#no shut

R3：

R3(config)#int s1/0

R3(config-if)#ip add 172.16.1.6 255.255.255.252

R3(config-if)#no shut

R3(config)#int s1/2

R3(config-if)#ip add 172.16.1.9 255.255.255.252

R3(config-if)#no shut

2、配置各台路由器的EIGRP协议,并且不关闭自动总结。例如在R上配置如下

   R1(config)#router eigrp 80

R1(config-router)#network 10.1.0.0

R1(config-router)#network 172.16.0.0

其它配置类似。

3、在R2上使用ping测试网络路由，会发现R2路由器无法ping通路由器R4所连接的10.1.X.0/24网络子网。如下所示：

  R2#ping 10.1.11.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.11.1, timeout is 2 seconds:

U.U.U

Success rate is 0 percent (0/5)

R2#ping 10.1.0.1

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.0.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 4/11/24 ms

R2#ping 10.1.13.1

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.13.1, timeout is 2 seconds:

U.U.U

Success rate is 0 percent (0/5)

可以看到，在R2去ping R1下带的网络地址10.1.0.1是通的，但ping R4下带的网络地址10.1.11.1 和10.1.13.1却是不通。潜意识下，查看R 2的路由表

R2#sh ip rout

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

 

Gateway of last resort is not set

 

     172.16.0.0/30 is subnetted, 3 subnets

D       172.16.1.8 [90/2681856] via 172.16.1.6, 00:13:03, Serial1/1

C       172.16.1.4 is directly connected, Serial1/1

C       172.16.1.0 is directly connected, Serial1/0

D    10.0.0.0/8 [90/2297856] via 172.16.1.1, 00:07:02, Serial1/0

D    192.168.0.0/24 [90/2297856] via 172.16.1.6, 00:12:44, Serial1/1

原来，R2已经将R1、R4的下带网络自动汇总成了10.0.0.0/8，已经不能分辨通往R1和R4的路由。但为什么它能通达R1而不能通达R4呢？

再来查看下R2 的拓扑数据库

R2#sh ip eigrp topology all-links

IP-EIGRP Topology Table for AS(80)/ID(172.16.1.5)

 

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

       r - reply Status, s - sia Status

 

P 10.0.0.0/8, 1 successors, FD is 2297856, serno 3

        via 172.16.1.1 (2297856/128256), Serial1/0

        via 172.16.1.6 (2809856/2297856), Serial1/1

P 192.168.0.0/24, 1 successors, FD is 2297856, serno 5

        via 172.16.1.6 (2297856/128256), Serial1/1

P 172.16.1.8/30, 1 successors, FD is 2681856, serno 4

        via 172.16.1.6 (2681856/2169856), Serial1/1

P 172.16.1.4/30, 1 successors, FD is 2169856, serno 2

        via Connected, Serial1/1

P 172.16.1.0/30, 1 successors, FD is 2169856, serno 1

        via Connected, Serial1/0

这里注意下这条命令sh ip eigrp topology all-links是显示所有的链路。

再细看粗字体，到达网络10.0.0.0/8是有两条路由的，并且两条路由的FD值是不同的。

R1、R4都是主类的边界，都会将本地路由表中的子网向主类网络自动汇总，因此R2会从不同的接口，收到相同的汇总路由，即 10.0.0 .0/8网络路由。R2在比较了两条路由的可行距离后，选择了较小的FD值的路由，即R1从接口s1/0向R2通告的10.0.0.0/8汇总路由，从而忽略了另外一个接口s1/1收到汇总路由。从这里可以看出，虽然EIGRP的自动汇总能够为网络配置带来便捷，但是其依赖于IP子网的良好规划。如果遇到糟糕的子网规划，则需要注意使用其自动特性。

4、找到了原因，解决问题就容易了。如果要顺利让R2 ping 通R4下带的网络，可以先关闭掉EIGRP的自动汇总，再重新在R1、R4上进行人工汇总。

R1：

R1(config)#router eigrp 80

R1(config-router)#no auto-summary

R1(config-router)#exit

R1(config)#int s1/0

R1(config-if)#ip summary-address eigrp 80 10.1.0.0 255.255.252.0

R1(config-if)#exit

注意上面是在R1与R2的接口s1/0的配置了人工的汇总，其汇总路由为 10.1.0 .0/22。R4：

R4(config)#router eigrp 50

R4(config-router)#no auto-summary

R4(config-router)#exit

R4(config)#

R4(config)#int s1/2

R4(config-if)#ip summary-address eigrp 80 10.1.10.0 255.255.252.0

配置好再查看R2的路由表，

R2#sh ip route

Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP

       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

       E1 - OSPF external type 1, E2 - OSPF external type 2

       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

       ia - IS-IS inter area, * - candidate default, U - per-user static route

       o - ODR, P - periodic downloaded static route

 

Gateway of last resort is not set

 

     172.16.0.0/30 is subnetted, 3 subnets

D       172.16.1.8 [90/2681856] via 172.16.1.6, 00:52:02, Serial1/1

C       172.16.1.4 is directly connected, Serial1/1

C       172.16.1.0 is directly connected, Serial1/0

     10.0.0.0/8 is variably subnetted, 7 subnets, 2 masks

D       10.1.8.0/22 [90/2809856] via 172.16.1.6, 00:25:14, Serial1/1

D       10.1.13.0/24 [90/2809856] via 172.16.1.6, 00:25:14, Serial1/1

D       10.1.12.0/24 [90/2809856] via 172.16.1.6, 00:25:14, Serial1/1

D       10.1.3.0/24 [90/2297856] via 172.16.1.1, 00:35:55, Serial1/0

D       10.1.2.0/24 [90/2297856] via 172.16.1.1, 00:35:55, Serial1/0

D       10.1.1.0/24 [90/2297856] via 172.16.1.1, 00:35:55, Serial1/0

D       10.1.0.0/24 [90/2297856] via 172.16.1.1, 00:35:55, Serial1/0

D    192.168.0.0/24 [90/2297856] via 172.16.1.6, 00:51:44, Serial1/1

可以看出R2已经将到达R4的路由汇总成了/22的路由。此时可以再在R2上用ping命令测试到达R1、R4的可达性。

R2#  ping 10.1.1.1

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 4/24/36 ms

R2#  ping 10.1.11.1

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.11.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 12/26/76 ms

R2#  ping 10.1.13.1

 

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.13.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 8/15/28 ms

可以看到，都通顺利地ping通R1、R4的下带网络了。