hostname R2
interface serial0/0
no ip address
encapsulation frame-relay
no frame-relay inverse-arp
interface serial0/0.12 point-to-point
description Link to R1
ip address 172.16.1.2 255.255.255.252
frame-relay interface-dlci 304
interface serial0/0.23 point-to-point
description Link to R3
ip address 172.16.1.5 255.255.255.252
frame-relay interface-dlci 302
router eigrp 16
passive-interface default
no passive-interface s0/0
network 172.16.1.0 0.0.0.255
auto-summary
此种情况下则在R2上, #show ip route eigrp, 则R2上无法学习到任何eigrp路由，原因这里no passive-interfaces应该是帧中继子接口serial0/0.12和serial0/0.23,而不是物理接口。
所以正确的配置为：
router eigrp 16
passive-interface default
no passive-interface serial0/0.12
no passive-interface serial0/0.23
network 172.16.1.0 0.0.0.255
auto-summary
或者：no passive-interface default
则配置变成：
router eigrp 16
network 172.16.1.0 0.0.0.255
auto-summary
