一、拓扑图：
二
、配置重分发进EIGRP 和IS-IS：
1、
配置三台路由器的IP地址与协议，配置完后，查看R1路由表：
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R1#sho 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
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 172.16.255.0/30 is directly connected, Serial1/1
C 172.16.1.0/24 is directly connected, Loopback0
C 172.16.2.0/24 is directly connected, Loopback0
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2、
查看R2的路由表，看到R2学到了全网的路由：
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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
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 172.16.255.0/30 is directly connected, Serial1/0
i L1 172.16.1.0/24 [115/20] via 172.16.255.1, Serial1/0
i L1 172.16.2.0/24 [115/20] via 172.16.255.1, Serial1/0
C 192.168.255.0/24 is directly connected, Serial1/1
D 192.168.1.0/24 [90/2297856] via 192.168.255.1, 05:25:40, Serial1/1
D 192.168.2.0/24 [90/2297856] via 192.168.255.1, 05:25:40, Serial1/1
R2#
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3
、那么我现在在R2上做重分发，一定要切记：要么R1和R2全用L1-2 类型，要么就用全用L1或L2类型，或者说当R1为L1，R2为L1-2，但这样你发布的时候要用L1-2类型做重分发，当R1和R2为L2类型的时候，R2重分发用L2或者L1-2类型重分发都能学到，同理L1也一样，如果R2不去手动指定类型，默认以L2默型发出去，所以当你在R1和R2都没指定类型的时候，也就是R1和R2都为L1-2。但R2却是以L2发出去，这样，R3就学不到R1发过去的路由了，如果R2指定类型，然后你重分发的时候不去指定类型，那么它将会和R2本身路由器的类型同步。（这是我一个一个去证明的，其实我们要注意的就是R1和R2是否是同类型或者是R2为L1-2类型，因为这样是可以搭配，然后在R2上把ISIS发到EIGRP的时候用同类型发布或L1-2发布就不会有问题。同时也要注意把EIGRP 发到ISIS中，默认不加类型都是以L2类型，要两面都要考虑，不然也会造成R1学不到R3那边的路由。
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R2(config)#router eigrp 100
R2(config-router)#redistribute connected
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5
、一切完毕，我们再看一下，R1的路由：
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R1#sh 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
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 172.16.255.0/30 is directly connected, Serial1/1
C 172.16.1.0/24 is directly connected, Loopback0
C 172.16.2.0/24 is directly connected, Loopback0
i L2 192.168.255.0/24 [115/84] via 172.16.255.2, Serial1/1
i L2 192.168.1.0/24 [115/84] via 172.16.255.2, Serial1/1
i L2 192.168.2.0/24 [115/84] via 172.16.255.2, Serial1/1
R1#
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R3
的路由：
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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
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
D EX 172.16.255.0/30 [170/2681856] via 192.168.255.2, 00:00:10, Serial1/0
D EX 172.16.1.0/24 [170/2172416] via 192.168.255.2, 00:00:10, Serial1/0
D EX 172.16.2.0/24 [170/2172416] via 192.168.255.2, 00:00:10, Serial1/0
C 192.168.255.0/24 is directly connected, Serial1/0
C 192.168.1.0/24 is directly connected, Loopback0
C 192.168.2.0/24 is directly connected, Loopback0
R3#
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6
、三条D EX外部重分发进来的路由全部学到.
总结：同一区域，L1或L2 都可以和L1-2搭配，在保证R2路由器学到全网路由后，路由器不同类型或同类型发布ISIS的时候都可以用类型L1-2重发布，不指定的话它会是默认L2重分发。同理发布EIGRP的时候如果同类型，可以同类型发布或者用L1-2。但不同类型只能用L1-2发布。总而言之：在建立起IS-IS邻居后，重分发的时候用L1-2是不会有错的，但是会增加IS-IS database ,如果概念清楚，用同类型最好了。所以说事物总是两面性的.
本文转自wxs-163 51CTO博客，原文链接:http://blog.51cto.com/supercisco/248835
