拓扑：
配置：
所有路由器全使用EIGRP路由协议，AS 90.
SHOW相关信息:
R4#show ip eigrp topology all-links
IP-EIGRP Topology Table for AS(90)/ID(10.1.1.1)
Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
r – reply Status, s – sia Status
P 10.1.1.0/24, 1 successors, FD is 128256, serno 55
via Connected, Loopback0
via 24.0.0.1 (2349056/435200), Serial1/1
P 24.0.0.0/24, 1 successors, FD is 2169856, serno 2
via Connected, Serial1/1
P 34.0.0.0/24, 1 successors, FD is 281600, serno 1
via Connected, FastEthernet0/1
via 24.0.0.1 (2221056/307200), Serial1/1
P 192.168.1.0/24, 1 successors, FD is 307200, serno 30
via 34.0.0.1 (307200/281600), FastEthernet0/1
via 24.0.0.1 (2195456/281600), Serial1/1
R4直连10.1.1.0网段。
R3#show ip eigrp topology all-links
IP-EIGRP Topology Table for AS(90)/ID(34.0.0.1)
Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
r – reply Status, s – sia Status
P 10.1.1.0/24, 1 successors, FD is 409600, serno 64
via 34.0.0.2 (409600/128256), FastEthernet0/1
P 24.0.0.0/24, 2 successors, FD is 2195456, serno 34
via 34.0.0.2 (2195456/2169856), FastEthernet0/1
via 192.168.1.2 (2195456/2169856), FastEthernet0/0
P 34.0.0.0/24, 1 successors, FD is 281600, serno 2
via Connected, FastEthernet0/1
P 192.168.1.0/24, 1 successors, FD is 281600, serno 33
via Connected, FastEthernet0/0
由于EIGRP水平分割影响，R3只能通过R4到达10.1.1.1
R2#show ip eigrp topology all-links
IP-EIGRP Topology Table for AS(90)/ID(24.0.0.1)
Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
r – reply Status, s – sia Status
P 10.1.1.0/24, 1 successors, FD is 435200, serno 90
via 192.168.1.3 (435200/409600), FastEthernet0/0
via 24.0.0.2 (2297856/128256), Serial1/1
P 24.0.0.0/24, 1 successors, FD is 2169856, serno 8
via Connected, Serial1/1
P 34.0.0.0/24, 1 successors, FD is 307200, serno 47
via 192.168.1.3 (307200/281600), FastEthernet0/0
via 24.0.0.2 (2195456/281600), Serial1/1
P 192.168.1.0/24, 1 successors, FD is 281600, serno 39
via Connected, FastEthernet0/0
via 24.0.0.2 (2221056/307200), Serial1/1
R2有两条链路可以通向10.1.1.0：
1、 通过R3，R3被选为Successor
2、 通过R4，R4被选为Feasible Successor
R1#show ip eigrp topology all-links
IP-EIGRP Topology Table for AS(90)/ID(13.0.0.1)
Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply,
r – reply Status, s – sia Status
P 10.1.1.0/24, 1 successors, FD is 435200, serno 69
via 192.168.1.3 (435200/409600), FastEthernet0/0
P 24.0.0.0/24, 1 successors, FD is 2195456, serno 39
via 192.168.1.2 (2195456/2169856), FastEthernet0/0
P 34.0.0.0/24, 1 successors, FD is 307200, serno 46
via 192.168.1.3 (307200/281600), FastEthernet0/0
P 192.168.1.0/24, 1 successors, FD is 281600, serno 31
via Connected, FastEthernet0/0
注意：由于水平分割，R1只有1条链路通向10.1.1.0。
通过各路由器的路由表可以得到以下示意图：
在所有路由器上通过命令debug eigrp packet query repay只观察我们需要的query和reply包。
在R4上通过接口命令：shutdown命令关闭lo 0来模拟该网络发生故障。下面通过各路由器的debug信息来观察他们的query 查询信息情况。
==R4 Debug ==
在F0/1口上发送关于10.1.1.0网络的查询包①（一下简称查询包），序列号是72。
*Mar 1 03:08:50.415: EIGRP: Sending QUERY on FastEthernet0/1
*Mar 1 03:08:50.415: AS 90, Flags 0×0, Seq 72/0 idbQ 0/0 iidbQ un/rely 0/0 serno 47-47
在S1/1口上发送查询包⑨，序列号是73。
*Mar 1 03:08:50.423: EIGRP: Sending QUERY on Serial1/1 nbr 24.0.0.1
*Mar 1 03:08:50.423: AS 90, Flags 0×0, Seq 73/104 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 47-47
在S1/1口上收到查询应答包⑩，Seq=105/73，序列号是105，73表示是对序列号为73的应答。
*Mar 1 03:08:50.923: EIGRP: Received REPLY on Serial1/1 nbr 24.0.0.1
*Mar 1 03:08:50.927: AS 90, Flags 0×0, Seq 105/73 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
在S1/1口上收到来自R2的查询应答包④
*Mar 1 03:08:51.175: EIGRP: Received QUERY on Serial1/1 nbr 24.0.0.1
*Mar 1 03:08:51.179: AS 90, Flags 0×0, Seq 107/73 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
10.1.1.0处于unreachable状态，所以向R2发出一个10.1.1.0不可达的查询应答⑤
*Mar 1 03:08:51.199: EIGRP: Sending REPLY on Serial1/1 nbr 24.0.0.1
*Mar 1 03:08:51.199: AS 90, Flags 0×0, Seq 74/107 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 48-48
在F0/1口上收到来自R2的查询应答包⑧，确认号是72，表示是对序列号为72的应答。
*Mar 1 03:08:52.223: EIGRP: Received REPLY on FastEthernet0/1 nbr 34.0.0.1
*Mar 1 03:08:52.227: AS 90, Flags 0×0, Seq 96/72 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
====R3 Debug ====
在F0/1口上收到来自R4的查询包①，序列号是72
*Mar 1 03:10:21.655: EIGRP: Received QUERY on FastEthernet0/1 nbr 34.0.0.2
*Mar 1 03:10:21.659: AS 90, Flags 0×0, Seq 72/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
②③在F0/0口上发送查询包，序列号是94
*Mar 1 03:10:21.679: EIGRP: Sending QUERY on FastEthernet0/0
*Mar 1 03:10:21.679: AS 90, Flags 0×0, Seq 94/0 idbQ 0/0 iidbQ un/rely 0/0 serno 56-56
在F0/0口上收到来自R1的查询应答包⑦，确认号是94，表示是对序列号为94的应答
*Mar 1 03:10:21.999: EIGRP: Received REPLY on FastEthernet0/0 nbr 192.168.1.1
*Mar 1 03:10:22.003: AS 90, Flags 0×0, Seq 77/94 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
在F0/0口上收到来自R2的查询应答包⑥，确认号是94，表示是对序列号为94的应答。
*Mar 1 03:10:22.871: EIGRP: Received REPLY on FastEthernet0/0 nbr 192.168.1.2
*Mar 1 03:10:22.875: AS 90, Flags 0×0, Seq 108/94 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
在F0/1口上向R4发出查询应答⑧，确认好是72，表示是对序列号为72的应答。
*Mar 1 03:10:23.243: EIGRP: Sending REPLY on FastEthernet0/1 nbr 34.0.0.2
*Mar 1 03:10:23.243: AS 90, Flags 0×0, Seq 96/72 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 57-57
====R1 Debug ====
在F0/0口上收到来自R3，序列号号是94的查询包②
*Mar 1 03:14:03.443: EIGRP: Received QUERY on FastEthernet0/0 nbr 192.168.1.3
*Mar 1 03:14:03.443: AS 90, Flags 0×0, Seq 94/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
在F0/0口上向R3发送查询应答⑦。
*Mar 1 03:14:03.467: EIGRP: Sending REPLY on FastEthernet0/0 nbr 192.168.1.3
*Mar 1 03:14:03.467: AS 90, Flags 0×0, Seq 77/94 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 63-63
====R2 Debug====
在S1/1口上收到来自R4，序列号是73的查询包⑨
*Mar 1 03:12:03.767: EIGRP: Received QUERY on Serial1/1 nbr 24.0.0.2
*Mar 1 03:12:03.767: AS 90, Flags 0×0, Seq 73/104 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
在F0/0口上收到来自R3，序列号是94的查询包③
*Mar 1 03:12:03.775: EIGRP: Received QUERY on FastEthernet0/0 nbr 192.168.1.3
*Mar 1 03:12:03.775: AS 90, Flags 0×0, Seq 94/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
在S1/1口上向R4发送查询应答，确认号是73，表示是对序列号为73的查询应答⑩
*Mar 1 03:12:03.803: EIGRP: Sending REPLY on Serial1/1 nbr 24.0.0.2
*Mar 1 03:12:03.803: AS 90, Flags 0×0, Seq 105/73 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 76-76
在S1/1口上向R4发送查询包，序列号是107 ④
*Mar 1 03:12:04.047: EIGRP: Sending QUERY on Serial1/1 nbr 24.0.0.2
*Mar 1 03:12:04.047: AS 90, Flags 0×0, Seq 107/73 idbQ 0/0 iidbQ un/rely 0/0
peerQ un/rely 0/1 serno 77-77
在S1/1口上收到来自R4的查询应答包，确认号是107，表示是对序列号为107的查询应答⑤
*Mar 1 03:12:04.419: EIGRP: Received REPLY on Serial1/1 nbr 24.0.0.2
*Mar 1 03:12:04.419: AS 90, Flags 0×0, Seq 74/107 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0
在F0/0口上向R3发送查询应答包，确认号是94，表示是对序列号是94的查询应答⑥
*Mar 1 03:12:04.875: EIGRP: Sending REPLY on FastEthernet0/0 nbr 192.168.1.3
*Mar 1 03:12:04.875: AS 90, Flags 0×0, Seq 108/94 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 78-78
以上是我们得到的各路由器的调试信息，只看调试信息可能会感觉比较混乱，请看下面的图示：
红色:query 蓝色:reply
1.当R4的lo0被手动DOWN掉后，R4将将该网段标注为unreachable，并向所有邻居发送查询包 (①和⑨)
2.R3收到来自successor R4的查询包①，将该10.1.1.0网段标注为unreachable，并从F0/0接口向组播地址224.0.0.10发送一个查询包(②和③是一个组播包)
3.当R1收到来自successor R3的查询包②，将10.1.1.0网段标注为unreachable。之后，本该向邻居R2发送查询包，但是通过R2到达10.1.1.0该目标网络的链路并没有被加进拓扑表，换句话说，R1认为，没有必要查询R2。R1向R3返回一个应答包⑦，表示通过R1不能到达目的网络。（关于R1为什么不向R2发送查询的解释被R4给否定，R4拓扑表中同样没有通过R3到达目标地址，但R4仍然向R3发出了查询。）？？？——这个问题希望同仁能帮我解答。
4.第一步的时候，R4向R2发出查询包⑨，当R2收到来自邻居R4的查询包后，紧接着收到来自successr R3的查询包，由于是来自successor，所以，R4将目标地址标注为unreachable,，之后，R2向R4返回目标地址不可达应答包⑩
5.当R2收到来自successor R3的查询包③，将该10.1.1.0网段标注为unreachable，并向邻居R4发送查询④。R4理所当然返回一个应答包⑤，表示通过R4不能到达目的网络。
6.R2收到来自邻居R4的不可达应答包⑤，表明R2已经没有能力到达指定目标网络，所以R2向R3返回目标地址不可达应答包⑥。
7.R3都收到来自邻居R1和R2关于目标地址不可达之后，表示通过R3也没有能力到达指定目标网络，所以，R3向R4返回目标地址不可达应答包⑧
8.当R4都收到来自邻居R2、R3的不可达应答包⑧⑩之后，最终确定10.1.1.0不可达，于是，R4将该路由条目从自己路由表中删除。
下面是cisco官方文档中关于EIGRP QUERY的查询解释：
