IP addresses and routing for the network are configured as shown in the exhibit． The network administrator issues the show ip eigrp neighbors command from Router1 and receives the output shown below the topology． Which statement is true?

A、 It is normal for Router1 to show one active neighbor at a time to prevent routing loops．
B、 Routing is not completely configured on Router3．
C、 The IP addresses are not configured properly on the Router1 and Router3 interfaces．
D、 The no auto-summary command configured on the routers prevents Router1 and Router2 from forming a neighbor relationship．

【正确答案】 B

【答案解析】在R3上只公告了192．168．2．0和10．0．0．0的网段，也只激活了接口S1和10．0．4．0的接口，而接口s0没有激活，因此R3与R1之间是无法建立邻居的。虽然R1会向R3的S0口发EIGRP的Hello包，但是R3是无法回复的。所以在R1上看到的EIGRP的邻居只有192．168．1．2。