一、拓扑图：
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二、配置各路由器的
IP地址使各直连链路互通。并配置
BGP协议，把直连网络宣告进
BGP，配置完之后，来看一下
R3的路由表：
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R3#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,5 subnets,2 masks
B 172.16.255.0/30 [20/0] via 10.1.255.1,02:28:27
B 172.16.0.0/24 [20/0] via 10.1.255.1,00:05:55
B 172.16.1.0/24 [20/0] via 10.1.255.1,00:05:25
B 172.16.2.0/24 [20/0] via 10.1.255.1,00:04:54
B 172.16.3.0/24 [20/0] via 10.1.255.1,00:04:54
10.0.0.0/30 is subnetted,1 subnets
C 10.1.255.0 is directly connected,Serial1/0
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三、在上一个实验中，因为使用静态路由指向空接口手动配置BGP汇总有不利于排错等弊端，现在换一种方式，我们在R1上用bgp聚合方法来配置汇总。但需要注意的是：如果只用aggregate-address通告聚合地址,那么聚合路由和详细路由都通告给对等体,如果在aggregate-address后加上关键字summary-only,那么将只通告聚合路由，不再通告具体的路由。
1、下面在R1上使用bgp聚合配置汇总路由：
1、下面在R1上使用bgp聚合配置汇总路由：
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R1(config)#router bgp 64512
R1(config-router)#aggregate-address 172.16.0.0 255.255.252.0 summary-only
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2、通过对R1的配置，再来看一下R3的路由表：
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R3#sh ip route
Codes: C - connected,B - BGP
D - EIGRP,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,L2 - IS-IS level-2
ia - IS-IS inter area,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,2 subnets,2 masks
B 172.16.255.0/30 [20/0] via 10.1.255.1,02:56:36
B 172.16.0.0/22 [20/0] via 10.1.255.1,00:02:34 (也能汇总成/22的汇总地址)
10.0.0.0/30 is subnetted,1 subnets
C 10.1.255.0 is directly connected,Serial1/0
R3#
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