1. 配置各接口所属的VLAN
[LSW1]vlan batch 10 30
[LSW1-GigabitEthernet0/0/2]port link-type trunk
[LSW1-GigabitEthernet0/0/2]port trunk allow-pass vlan 10
[LSW1-GigabitEthernet0/0/3]port link-type trunk
[LSW1-GigabitEthernet0/0/3]port trunk allow-pass vlan 30
[LSW2]vlan batch 10 20
[LSW2-GigabitEthernet0/0/1]port link-type trunk
[LSW2-GigabitEthernet0/0/1]port trunk allow-pass vlan 10
[LSW2-GigabitEthernet0/0/3]port link-type trunk
[LSW2-GigabitEthernet0/0/3]port trunk allow-pass vlan 20
[LSW3]vlan batch 20 30
[LSW3-GigabitEthernet0/0/2]port link-type trunk
[LSW3-GigabitEthernet0/0/2]port trunk allow-pass vlan 20
[LSW3-GigabitEthernet0/0/1]port link-type trunk
[LSW3-GigabitEthernet0/0/1]port trunk allow-pass vlan 30
2. 配置各VLANIF接口的IP地址
[LSW1-Vlanif10]ip add 10.1.1.1 24
[LSW1-Vlanif30]ip add 10.1.3.1 24
[LSW2-Vlanif10]ip add 10.1.1.2 24
[LSW2-Vlanif20]ip add 10.1.2.2 24
[LSW3-Vlanif20]ip add 10.1.2.3 24
[LSW3-Vlanif30]ip add 10.1.3.3 24
[LSW1]stp disable
[LSW2]stp disable
[LSW3]stp disable
3. 配置BGP连接
[LSW1]bgp 65008
[LSW1-bgp]router-id 1.1.1.1.
[LSW1-bgp]peer 10.1.1.2 as-number 65009
[LSW1-bgp]peer 10.1.3.3 as-number 65009
[LSW2]bgp 65009
[LSW2-bgp]router-id 2.2.2.2
[LSW2-bgp]peer 10.1.1.1 as-number 65008
[LSW2-bgp]peer 10.1.2.3 as-number 65009
[LSW2-bgp]ipv6-family unicast
[LSW2-bgp-af-ipv6]network 10.1.2.0 255.255.255.0
[LSW3]bgp 65009
[LSW3-bgp]router-id 3.3.3.3
[LSW3-bgp]peer 10.1.3.1 as-number 65008
[LSW3-bgp]peer 10.1.2.2 as-number 65009
[LSW3-bgp]ipv4-family unicast
[LSW3-bgp-af-ipv4]network 10.1.2.0 255.255.255.0
可以看出到目的地址10.1.2.0/24有两条有效路由，其中下一跳为10.1.1.2的路由是最优路由（因为LSW2的Router ID要小一些）
4. 配置负载分担
[LSW1]bgp 65008
[LSW1-bgp]ipv4-family unicast
[LSW1-bgp-af-ipv4]maximum load-balancing 2
可以看出即使配置了负载分担，到目的地址10.1.2.0/24的有效路由还是10.1.1.2
5. 通过策略路由增大LSW2发送给LSW1的MED，而BGP优先选择MED值较小的路由，从而优选10.1.3.3为有效路由
[LSW2]route-policy 10 permit node 10
[LSW2-route-policy]apply cost 100
[LSW2]bgp 65009
[LSW2-bgp]peer 10.1.1.1 route-policy 10 export
6. 验证配置
