EIGRP的汇总是汇总在出接口，并且如果EIGRP路由传递的时候有两个出接口的话那么两个接口都要进行汇总。使用拓扑如下：
R1：
username r2 password 0 cisco
!
interface Loopback3
ip address 160.1.16.1 255.255.255.0
!
interface Loopback4
ip address 160.1.17.1 255.255.255.0
!
interface Loopback5
ip address 160.1.18.1 255.255.255.0
!
interface Loopback6
ip address 160.1.19.1 255.255.255.0
!
interface Serial0/1
ip address 170.1.12.1 255.255.255.0
encapsulation ppp
ip summary-address eigrp 100 160.1.16.0 255.255.252.0 5
serial restart-delay 0
ppp authentication chap
ppp chap hostname r1
ppp chap password 0 cisco
!
interface Ethernet1/0
ip address 170.1.21.1 255.255.255.0
ip summary-address eigrp 100 160.1.16.0 255.255.252.0 5
half-duplex
router eigrp 100
network 160.1.16.1 0.0.0.0
network 160.1.17.1 0.0.0.0
network 160.1.18.1 0.0.0.0
network 160.1.19.1 0.0.0.0
network 170.1.12.1 0.0.0.0
network 170.1.21.1 0.0.0.0
no auto-summary
ip dhcp excluded-address 170.1.21.1
!
ip dhcp pool togogo
network 170.1.21.0 255.255.255.0
default-router 170.1.21.1
dns-server 8.8.8.8
R2：
username r1 password 0 cisco
interface Serial0/0
ip address 170.1.12.2 255.255.255.0
encapsulation ppp
serial restart-delay 0
ppp authentication chap
ppp chap hostname r2
ppp chap password 0 cisco
!
interface Ethernet1/0
ip address dhcp
half-duplex
router eigrp 100
variance 6
network 170.1.12.2 0.0.0.0
network 170.1.21.2 0.0.0.0
no auto-summary
实验结果：
R2(config-if)#do sh ip rou ei
160.1.0.0/22 is subnetted, 1 subnets
D 160.1.16.0 [90/409600] via 170.1.21.1, 00:00:37, Ethernet1/0
[90/2297856] via 170.1.12.1, 00:00:37, Serial0/0
