1) 按照拓扑搭建网络，在所有AS间使用直连接口建立EBGP邻居关系；
2) 在公司总部AS400中，R4与R5，R5与R7，R7与R6，R6与R4间使用环回接口建立IBGP邻居关系，IGP协议使用OSPF；
3) 所有业务网段，与所有设备上的Loopback 0所在网段都能通过BGP路由实现互相访问；
4) 为了使网络资源能充分得到利用，要求业务网段A的流量通过运营商设备转发，业务网段B的流量通过专线转发；
5) 网络管理员进行定期线路检查，现通过适当调整IGP的链路开销值，使得所有经过总部AS的流量都沿着R4-R5-R7-R6路径转发；
6) 网络管理员在检查中发现业务网段B的流量非常大，决定将业务网段B的流量单独沿着R4-R6路径转发（要求BGP路由选路与实际转发路径一致）；
7) 公司总部网络将进行改造，在不改变原有配置的基础上，通过增加少量配置实现，R5与R7不参与BGP路径选择。
1) 按照拓扑搭建网络，在所有AS间使用直连接口建立EBGP邻居关系；
R1:（为例）R1R2R3R4R6都做
bgp 100
peer 12.1.1.2 as-number 200
peer 14.1.1.4 as-number 400
2) 在公司总部AS400中，R4与R5，R5与R7，R7与R6，R6与R4间使用环回接口建立IBGP邻居关系，IGP协议使用OSPF；
R4为例（R4R5R6R7都做）bgp 400
peer 5.5.5.5 as-number 400
peer 5.5.5.5 connect-interface LoopBack0
peer 6.6.6.6 as-number 400
peer 6.6.6.6 connect-interface LoopBack0
peer 7.7.7.7 as-number 400
peer 7.7.7.7 connect-interface LoopBack0
peer 14.1.1.1 as-number 100
import-route ospf 1
ospf 1 router-id 4.4.4.4
area 0.0.0.0
network 4.4.4.0 0.0.0.255
network 5.5.5.0 0.0.0.255
network 45.1.1.0 0.0.0.255
network 46.1.1.0 0.0.0.255
3) 所有业务网段，与所有设备上的Loopback 0所在网段都能通过BGP路由实现互相访问；
前3问之前R1到R7的所有命令：
R1:
interface GigabitEthernet0/0/0
ip address 12.1.1.1 255.255.255.0
#
interface GigabitEthernet0/0/1
ip address 14.1.1.1 255.255.255.0
#
interface GigabitEthernet0/0/2
#
interface NULL0
#
interface LoopBack0
ip address 1.1.1.1 255.255.255.0
#
interface LoopBack1
ip address 11.11.11.11 255.255.255.0
#
bgp 100
peer 12.1.1.2 as-number 200
peer 14.1.1.4 as-number 400
#
ipv4-family unicast
undo synchronization
network 1.1.1.0 255.255.255.0
network 11.11.11.0 255.255.255.0
peer 12.1.1.2 enable
peer 14.1.1.4 enable
#
ip route-static 2.2.2.0 255.255.255.0 12.1.1.2
ip route-static 4.4.4.0 255.255.255.0 14.1.1.4
#
user-interface con 0
authentication-mode password
user-interface vty 0 4
user-interface vty 16 20
#
wlan ac
#
return
R2:
interface GigabitEthernet0/0/0
ip address 12.1.1.2 255.255.255.0
#
interface GigabitEthernet0/0/1
ip address 23.1.1.2 255.255.255.0
#
interface GigabitEthernet0/0/2
#
interface NULL0
#
interface LoopBack0
ip address 2.2.2.2 255.255.255.0
#
interface LoopBack1
ip address 22.22.22.22 255.255.255.0
#
bgp 200
peer 12.1.1.1 as-number 100
peer 23.1.1.3 as-number 300
#
ipv4-family unicast
undo synchronization
network 2.2.2.0 255.255.255.0
network 22.22.22.0 255.255.255.0
peer 12.1.1.1 enable
peer 23.1.1.3 enable
#
ip route-static 1.1.1.0 255.255.255.0 12.1.1.1
ip route-static 3.3.3.0 255.255.255.0 23.1.1.3
#
user-interface con 0
authentication-mode password
user-interface vty 0 4
user-interface vty 16 20
#
wlan ac
#
return
R3:
interface GigabitEthernet0/0/0
ip address 23.1.1.3 255.255.255.0
#
interface GigabitEthernet0/0/1
ip address 36.1.1.3 255.255.255.0
#
interface GigabitEthernet0/0/2
#
interface NULL0
#
interface LoopBack0
ip address 3.3.3.3 255.255.255.0
#
interface LoopBack1
ip address 33.33.33.33 255.255.255.0
#
bgp 300
peer 23.1.1.2 as-number 200
peer 36.1.1.6 as-number 400
#
ipv4-family unicast
undo synchronization
network 3.3.3.0 255.255.255.0
network 33.33.33.0 255.255.255.0
peer 23.1.1.2 enable
peer 36.1.1.6 enable
#
ip route-static 2.2.2.0 255.255.255.0 23.1.1.2
ip route-static 6.6.6.0 255.255.255.0 36.1.1.6
#
user-interface con 0
authentication-mode password
user-interface vty 0 4
user-interface vty 16 20
#
wlan ac
#
R4:
interface GigabitEthernet0/0/0
ip address 14.1.1.4 255.255.255.0
#
interface GigabitEthernet0/0/1
ip address 46.1.1.4 255.255.255.0
#
interface GigabitEthernet0/0/2
ip address 45.1.1.4 255.255.255.0
#
interface NULL0
#
interface LoopBack0
ip address 4.4.4.4 255.255.255.0
#
interface LoopBack1
ip address 44.44.44.44 255.255.255.0
#
bgp 400
peer 5.5.5.5 as-number 400
peer 5.5.5.5 connect-interface LoopBack0
peer 6.6.6.6 as-number 400
peer 6.6.6.6 connect-interface LoopBack0
peer 7.7.7.7 as-number 400
peer 7.7.7.7 connect-interface LoopBack0
peer 14.1.1.1 as-number 100
#
ipv4-family unicast
undo synchronization
network 4.4.4.0 255.255.255.0
network 44.44.44.0 255.255.255.0
import-route ospf 1
peer 5.5.5.5 enable
peer 5.5.5.5 next-hop-local
peer 6.6.6.6 enable
peer 6.6.6.6 next-hop-local
peer 7.7.7.7 enable
peer 7.7.7.7 next-hop-local
peer 14.1.1.1 enable
#
ospf 1 router-id 4.4.4.4
area 0.0.0.0
network 4.4.4.0 0.0.0.255
network 5.5.5.0 0.0.0.255
network 45.1.1.0 0.0.0.255
network 46.1.1.0 0.0.0.255
#
ip route-static 1.1.1.0 255.255.255.0 14.1.1.1
#
user-interface con 0
authentication-mode password
user-interface vty 0 4
user-interface vty 16 20
#
wlan ac
#
R5:
interface GigabitEthernet0/0/0
ip address 45.1.1.5 255.255.255.0
#
interface GigabitEthernet0/0/1
ip address 57.1.1.5 255.255.255.0
#
interface GigabitEthernet0/0/2
#
interface NULL0
#
interface LoopBack0
ip address 5.5.5.5 255.255.255.0
#
bgp 400
peer 4.4.4.4 as-number 400
peer 4.4.4.4 connect-interface LoopBack0
peer 6.6.6.6 as-number 400
peer 6.6.6.6 connect-interface LoopBack0
peer 7.7.7.7 as-number 400
peer 7.7.7.7 connect-interface LoopBack0
#
ipv4-family unicast
undo synchronization
peer 4.4.4.4 enable
peer 4.4.4.4 next-hop-local
peer 6.6.6.6 enable
peer 6.6.6.6 next-hop-local
peer 7.7.7.7 enable
peer 7.7.7.7 next-hop-local
#
ospf 1 router-id 5.5.5.5
area 0.0.0.0
network 4.4.4.0 0.0.0.255
network 5.5.5.0 0.0.0.255
network 7.7.7.0 0.0.0.255
network 45.1.1.0 0.0.0.255
network 57.1.1.0 0.0.0.255
#
user-interface con 0
authentication-mode password
user-interface vty 0 4
user-interface vty 16 20
#
wlan ac
R6:
interface GigabitEthernet0/0/0
ip address 36.1.1.6 255.255.255.0
#
interface GigabitEthernet0/0/1
ip address 46.1.1.6 255.255.255.0
#
interface GigabitEthernet0/0/2
ip address 67.1.1.6 255.255.255.0
#
interface NULL0
#
interface LoopBack0
ip address 6.6.6.6 255.255.255.0
#
interface LoopBack1
ip address 66.66.66.66 255.255.255.0
#
bgp 400
peer 4.4.4.4 as-number 400
peer 4.4.4.4 connect-interface LoopBack0
peer 5.5.5.5 as-number 400
peer 5.5.5.5 connect-interface LoopBack0
peer 7.7.7.7 as-number 400
peer 7.7.7.7 connect-interface LoopBack0
peer 36.1.1.3 as-number 300
#
ipv4-family unicast
undo synchronization
network 6.6.6.0 255.255.255.0
network 66.66.66.0 255.255.255.0
import-route ospf 1
peer 4.4.4.4 enable
peer 4.4.4.4 next-hop-local
peer 5.5.5.5 enable
peer 5.5.5.5 next-hop-local
peer 7.7.7.7 enable
peer 7.7.7.7 next-hop-local
peer 36.1.1.3 enable
#
ospf 1 router-id 6.6.6.6
area 0.0.0.0
network 6.6.6.0 0.0.0.255
network 7.7.7.0 0.0.0.255
network 46.1.1.0 0.0.0.255
network 67.1.1.0 0.0.0.255
#
ip route-static 3.3.3.0 255.255.255.0 36.1.1.3
#
user-interface con 0
authentication-mode password
user-interface vty 0 4
user-interface vty 16 20
#
wlan ac
#
return
R7:
#
interface GigabitEthernet0/0/0
ip address 57.1.1.7 255.255.255.0
#
interface GigabitEthernet0/0/1
ip address 67.1.1.7 255.255.255.0
#
interface GigabitEthernet0/0/2
#
interface NULL0
#
interface LoopBack0
ip address 7.7.7.7 255.255.255.0
#
bgp 400
peer 4.4.4.4 as-number 400
peer 4.4.4.4 connect-interface LoopBack0
peer 5.5.5.5 as-number 400
peer 5.5.5.5 connect-interface LoopBack0
peer 6.6.6.6 as-number 400
peer 6.6.6.6 connect-interface LoopBack0
#
ipv4-family unicast
undo synchronization
peer 4.4.4.4 enable
peer 4.4.4.4 next-hop-local
peer 5.5.5.5 enable
peer 5.5.5.5 next-hop-local
peer 6.6.6.6 enable
peer 6.6.6.6 next-hop-local
#
ospf 1 router-id 7.7.7.7
area 0.0.0.0
network 5.5.5.0 0.0.0.255
network 6.6.6.0 0.0.0.255
network 7.7.7.0 0.0.0.255
network 57.1.1.0 0.0.0.255
network 67.1.1.0 0.0.0.255
#
user-interface con 0
authentication-mode password
user-interface vty 0 4
user-interface vty 16 20
#
wlan ac
4) 为了使网络资源能充分得到利用，要求业务网段A的流量通过运营商设备转发，业务网段B的流量通过专线转发；