一、拓扑图
二、需求
1、使用PreVal策略，确保R4通过R2到达192.168.10.0/24
2、使用AS_Path策略，确保R4通过R3到达192.168.11.0/24
3、配置MED策略，确保R4通过R3到达192.168.12.0/24
4、使用Local Preference策略，确保R1通过R2到达192.168.1.0/24
5、使用Local Preference策略，确保R1通过R3到达192.168.2.0/24
6、配置负载均衡，确保R1通过R2和R3到达192.168.3.0/24
7、使用AS策略，AS 500不接受任何始发于AS 123的路由
8、使用自定义Community策略，确保192.168.3.0/24路由不会被发布到AS 500
9、IBGP使用环回接口建邻，EBGP使用物理接口建邻
10、修改AS 123中的用户网段为Broadcast，方便后续在BGP中宣告
11、BGP宣告路由时，仅宣告24网段的用户路由
三、需求分析
1、根据需求配置所有IP地址
2、配置OSPF协议
3、配置BGP协议并将环回接口修改为相同类型
4、宣告BGP路由
5、R4使用PreVal策略、AS_Path策略和MED策略
6、R1使用Local Preference策略并配置负载均衡
7、R5使用AS策略
8、R2、R3、R4使用自定义Community策略
四、所有配置的文字描述及代码
1、配置IP地址
#r1
[r1]int g 0/0/0
[r1-GigabitEthernet0/0/0]ip address 12.0.0.1 24
[r1-GigabitEthernet0/0/0]int g 0/0/1
[r1-GigabitEthernet0/0/1]ip address 13.0.0.1 24
[r1-GigabitEthernet0/0/1]int g 0/0/2
[r1-GigabitEthernet0/0/2]ip address 15.0.0.1 24
[r1-GigabitEthernet0/0/2]int l 0
[r1-LoopBack0]ip address 1.1.1.1 32
[r1-LoopBack0]int l 1
[r1-LoopBack1]ip address 192.168.100.1 24#r2
[r2]int g 0/0/0
[r2-GigabitEthernet0/0/0]ip address 24.0.0.2 24
[r2-GigabitEthernet0/0/0]int g 0/0/1
[r2-GigabitEthernet0/0/1]ip address 12.0.0.2 24
[r2-GigabitEthernet0/0/1]int l 0
[r2-LoopBack0]ip address 2.2.2.2 32
[r2-LoopBack0]int l 1
[r2-LoopBack1]ip address 192.168.20.1 24#r3
[r3]int g 0/0/0
[r3-GigabitEthernet0/0/0]ip address 34.0.0.3 24
[r3-GigabitEthernet0/0/0]int g 0/0/1
[r3-GigabitEthernet0/0/1]ip address 13.0.0.3 24
[r3-GigabitEthernet0/0/1]int l 0
[r3-LoopBack0]ip address 3.3.3.3 32
[r3-LoopBack0]int l 1
[r3-LoopBack1]ip address 192.168.30.1 24#r4
[r4]int g 0/0/0
[r4-GigabitEthernet0/0/0]ip address 24.0.0.4 24
[r4-GigabitEthernet0/0/0]int g 0/0/1
[r4-GigabitEthernet0/0/1]ip address 34.0.0.4 24
[r4-GigabitEthernet0/0/1]int l 0
[r4-LoopBack0]ip address 192.168.1.1 24
[r4-LoopBack0]int l 1
[r4-LoopBack1]ip address 192.168.2.1 24
[r4-LoopBack1]int l 2
[r4-LoopBack2]ip address 192.168.3.1 24#r5
[r5]int g 0/0/0
[r5-GigabitEthernet0/0/0]ip address 15.0.0.5 24
[r5-GigabitEthernet0/0/0]int l 0
[r5-LoopBack0]ip address 192.168.10.1 24
[r5-LoopBack0]int l 1
[r5-LoopBack1]ip address 192.168.11.1 24
[r5-LoopBack1]int l 2
[r5-LoopBack2]ip address 192.168.12.1 242、配置OSPF协议
#r1
[r1]ospf 1 router-id 1.1.1.1
[r1-ospf-1]a 0
[r1-ospf-1-area-0.0.0.0]network 1.1.1.1 0.0.0.0
[r1-ospf-1-area-0.0.0.0]network 12.0.0.1 0.0.0.0
[r1-ospf-1-area-0.0.0.0]network 13.0.0.1 0.0.0.0
[r1-ospf-1-area-0.0.0.0]network 192.168.100.1 0.0.0.0#r2
[r2]ospf 1 router-id 2.2.2.2
[r2-ospf-1]a 0
[r2-ospf-1-area-0.0.0.0]network 2.2.2.2 0.0.0.0
[r2-ospf-1-area-0.0.0.0]network 12.0.0.2 0.0.0.0
[r2-ospf-1-area-0.0.0.0]network 192.168.20.1 0.0.0.0#r3
[r3]ospf 1 router-id 3.3.3.3
[r3-ospf-1]a 0
[r3-ospf-1-area-0.0.0.0]network 3.3.3.3 0.0.0.0
[r3-ospf-1-area-0.0.0.0]network 13.0.0.3 0.0.0.0
[r3-ospf-1-area-0.0.0.0]network 192.168.30.1 0.0.0.0联通测试：
3、配置BGP协议
#r1
[r1]bgp 123
[r1-bgp]router-id 1.1.1.1
[r1-bgp]peer 2.2.2.2 as-number 123
[r1-bgp]peer 2.2.2.2 connect-interface LoopBack 0
[r1-bgp]peer 2.2.2.2 next-hop-local
[r1-bgp]peer 3.3.3.3 as-number 123
[r1-bgp]peer 3.3.3.3 connect-interface LoopBack 0
[r1-bgp]peer 3.3.3.3 next-hop-local
[r1-bgp]peer 15.0.0.5 as-number 500#r2
[r2]bgp 123
[r2-bgp]router-id 2.2.2.2
[r2-bgp]peer 1.1.1.1 as-number 123
[r2-bgp]peer 1.1.1.1 connect-interface LoopBack 0
[r2-bgp]peer 1.1.1.1 next-hop-local
[r2-bgp]peer 24.0.0.4 as-number 400#r3
[r3]bgp 123
[r3-bgp]router-id 3.3.3.3
[r3-bgp]peer 1.1.1.1 as-number 123
[r3-bgp]peer 1.1.1.1 connect-interface LoopBack 0
[r3-bgp]peer 1.1.1.1 next-hop-local
[r3-bgp]peer 34.0.0.4 as-number 400#r4
[r4]bgp 400
[r4-bgp]router-id 4.4.4.4
[r4-bgp]peer 24.0.0.2 as-number 123
[r4-bgp]peer 34.0.0.3 as-number 123#r5
[r5]bgp 500
[r5-bgp]router-id 5.5.5.5
[r5-bgp]peer 15.0.0.1 as-number 123查看配置情况： 
将R1、R2、R3环回接口修改为相同类型
#r1
[r1]int l 1
[r1-LoopBack1]ospf network-type broadcast #r2
[r2]int l 1
[r2-LoopBack1]ospf network-type broadcast #r3
[r3]int l 1
[r3-LoopBack1]ospf network-type broadcast 4、宣告BGP路由
#r1
[r1]bgp 123
[r1-bgp]network 192.168.100.0 24#r2
[r2]bgp 123
[r2-bgp]network 192.168.20.0 24#r3
[r3]bgp 123
[r3-bgp]network 192.168.30.0 24#r4
[r4]bgp 400
[r4-bgp]network 192.168.1.0 24
[r4-bgp]network 192.168.2.0 24
[r4-bgp]network 192.168.3.0 24#r5
[r5]bgp 500
[r5-bgp]network 192.168.10.0 24
[r5-bgp]network 192.168.11.0 24
[r5-bgp]network 192.168.12.0 245、R4使用PreVal策略
[r4]ip ip-prefix PV permit 192.168.10.0 24
[r4]route-policy PV permit node 10
Info: New Sequence of this List.
[r4-route-policy]if-match ip-prefix PV
[r4-route-policy]apply preferred-value 100
[r4-route-policy]q
[r4]route-p
[r4]route-policy PV permit node 80
Info: New Sequence of this List.
[r4-route-policy]q
[r4]bgp 400
[r4-bgp]peer 24.0.0.2 route-policy PV import 
6、R4使用AS_Path策略
[r4]ip ip-prefix AS permit 192.168.11.0 24
[r4]route-policy AS permit node 10
Info: New Sequence of this List.
[r4-route-policy]if-match ip-prefix AS
[r4-route-policy]apply as-path 123 overwrite 
7、R4使用MED策略
8、R1使用Local Preference策略
[r1]ip ip-prefix LP permit 192.168.1.0 24
[r1]route-policy LP permit node 10
Info: New Sequence of this List.
[r1-route-policy]if-match ip-prefix LP
[r1-route-policy]apply local-preference 200
[r1-route-policy]q
[r1]bgp 123
[r1-bgp]peer 2.2.2.2 route-policy LP import
[r1]ip ip-prefix LP1 permit 192.168.2.0 24
[r1]route-policy LP1 permit node 10
Info: New Sequence of this List.
[r1-route-policy]if-match ip-prefix LP1
[r1-route-policy]apply local-preference 200
[r1-route-policy]q
[r1]route-policy LP1 permit node 20
Info: New Sequence of this List.
[r1-route-policy]q
[r1]bgp 123
[r1-bgp]peer 3.3.3.3 route-policy LP1 import
9、R1配置负载均衡
[r1]bgp 123
[r1-bgp]maximum load-balancing 2
10、R5使用AS策略
[r5]ip as-path-filter 1 deny _123$
[r5]ip as-path-filter 1 permit .*
[r5]bgp 500
[r5-bgp]peer 15.0.0.1 as-path-filter 1 export 
11、R2、R3、R4使用自定义Community策略
#r2
[r2]bgp 123
[r2-bgp]peer 1.1.1.1 advertise-community
[r2-bgp]q
[r2]ip community-filter 1 permit 400:111
[r2]route-policy com deny node 10
Info: New Sequence of this List.
[r2-route-policy]if-match community-filter 1
[r2-route-policy]apply community no-export additive
[r2-route-policy]q
[r2]route-policy com permit node 100
Info: New Sequence of this List.
[r2-route-policy]q[r4]route-policy com-1 permit node 10
Info: New Sequence of this List.
[r2]bgp 123
[r2-bgp]peer 24.0.0.4 route-policy com import #r3
[r3]bgp 123
[r3-bgp]peer 1.1.1.1 advertise-community
[r3-bgp]q
[r3]ip community-filter 1 permit 400:111
[r3]route-policy com deny node 10
Info: New Sequence of this List.
[r3-route-policy]if-match community-filter 1
[r3-route-policy]apply community no-export additive
[r3-route-policy]q
[r3]route-policy com permit node 100
Info: New Sequence of this List.
[r3-route-policy]q
[r3]bgp 123
[r3-bgp]peer 34.0.0.4 route-policy com import #r4
[r4]route-policy com-1 permit node 10
Info: New Sequence of this List.
[r4-route-policy]apply community 400:111
[r4-route-policy]q
[r4]bgp 400
[r4-bgp]network 192.168.3.0 24 route-policy com-1
[r4-bgp]peer 24.0.0.2 advertise-ext-community
[r4-bgp]peer 34.0.0.3 advertise-ext-community查看情况：
