Note:
被Auto-summary命令汇总成的主类网络号的所有子网的查询可以在汇总点被结束。
解释：
汇总点：如图，R2上开启auto-summary，对于10.2.2.0/24和10.1.1.0/24来讲，R3就是他们的汇总点。对于23.1.1.0/24来说，R1是他们的汇总点。
拓扑：
配置：
R1配置：
lo0:10.1.1.1/24
f0/0:10.2.2.1/24
跑eigrp协议，AS 90，用命令no auto-summary关闭自动汇总
R2配置：
F0/0:10.2.2.2/24
F0/1:23.1.1.1/24
跑eigrp协议，AS 90，默认开启auto-summary自动汇总。
其余路由器均跑EIGRP协议，AS 90。
按以上配置，可以猜测在R3上可以得到这样一条路由：
D 10.0.0.0/8 via 23.1.1.1
验证：
R1#show ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 10.2.2.1 YES manual up up
Loopback0 10.1.1.1 YES manual up up
R2#show ip int b
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 10.2.2.2 YES manual up up
FastEthernet0/1 23.1.1.1 YES manual up up
R2#show 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
34.0.0.0/24 is subnetted, 1 subnets
D 34.1.1.0 [90/307200] via 23.1.1.2, 00:35:40, FastEthernet0/1
23.0.0.0/24 is subnetted, 1 subnets
C 23.1.1.0 is directly connected, FastEthernet0/1
10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks
C 10.2.2.0/24 is directly connected, FastEthernet0/0
D 10.1.1.0/24 [90/409600] via 10.2.2.1, 00:01:32, FastEthernet0/0
D 10.0.0.0/8 is a summary, 00:20:17, Null0
R2将直连的10.2.2.0/24汇总成10.0.0.0/8，并且R2学习到了R1的回环口网络10.1.1.0/24
R3#show 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
34.0.0.0/24 is subnetted, 1 subnets
C 34.1.1.0 is directly connected, FastEthernet0/0
20.0.0.0/24 is subnetted, 1 subnets
D 20.1.1.0 [90/435200] via 23.1.1.1, 00:22:55, FastEthernet0/1
23.0.0.0/24 is subnetted, 1 subnets
C 23.1.1.0 is directly connected, FastEthernet0/1
D 10.0.0.0/8 [90/307200] via 23.1.1.1, 00:22:05, FastEthernet0/1
R3路由表确实学习到被R2汇总成的10.0.0.0/8主类网络。
下面在R1的lo0上通过shutdown命令将环回口0关闭，模拟网络故障，让R1发出关于10.1.1.0/24的查询。在关闭接口之前，先在R1~R4上打开调试命令debug eigrp packet query。
R1(config)#int lo 0
R1(config-if)#shut
观察各路由器debug信息
===R1 debug===
*Mar 1 01:55:40.483: EIGRP: Sending QUERY on FastEthernet0/0
===R2 debug===
*Mar 1 01:54:03.139: EIGRP: Received QUERY on FastEthernet0/0 nbr 10.2.2.1
*Mar 1 01:54:03.171: EIGRP: Sending QUERY on FastEthernet0/1
===R3 debug===
*Mar 1 01:52:22.287: EIGRP: Received QUERY on FastEthernet0/1 nbr 23.1.1.1
观察发现：R1向R2发送查询，R2在收到R1的查询后，继续向R3发送查询，查询被R3结束，没有继续向R4发送。