1. 在MPLS骨干网上配置IGP协议，实现骨干网PE和P的互通
[PE1-LoopBack1]ip add 1.1.1.1 32
[PE1-GigabitEthernet0/0/0]ip add 20.1.1.1 24
[PE1]isis 1
[PE1-isis-1]network-entity 10.0000.0000.0001.00
[PE1-LoopBack1]isis enable 1
[PE1-GigabitEthernet0/0/0]isis enable 1
[P1-LoopBack1]ip add 2.2.2.2 32
[P1-GigabitEthernet0/0/0]ip add 20.1.1.2 24
[P1-GigabitEthernet0/0/1]ip add 30.1.1.2 24
[P1]isis 1
[P1-isis-1]network-entity 10.0000.0000.0002.00
[P1-LoopBack1]isis enable 1
[P1-GigabitEthernet0/0/0]isis enable 1
[P1-GigabitEthernet0/0/1]isis enable 1
[PE3-LoopBack1]ip add 3.3.3.3 32
[PE3-GigabitEthernet0/0/0]ip add 30.1.1.3 24
[PE3]isis 1
[PE3-isis-1]network-entity 10.0000.0000.0003.00
[PE3-LoopBack1]isis enable 1
[PE3-GigabitEthernet0/0/0]isis enable 1
[PE2-LoopBack1]ip add 4.4.4.4 32
[PE2-GigabitEthernet0/0/0]ip add 40.1.1.4 24
[PE2]isis 1
[PE2-isis-1]network-entity 10.0000.0000.0004.00
[PE2-LoopBack1]isis enable 1
[PE2-GigabitEthernet0/0/0]isis enable 1
[P2-LoopBack1]ip add 5.5.5.5 32
[P2-GigabitEthernet0/0/0]ip add 40.1.1.5 24
[P2-GigabitEthernet0/0/1]ip add 50.1.1.5 24
[P2]isis 1
[P2-isis-1]network-entity 10.0000.0000.0005.00
[P2-LoopBack1]isis enable 1
[P2-GigabitEthernet0/0/0]isis enable 1
[P2-GigabitEthernet0/0/1]isis enable 1
[PE4-LoopBack1]ip add 6.6.6.6 32
[PE4-GigabitEthernet0/0/0]ip add 50.1.1.6 24
[PE4]isis 1
[PE4-isis-1]network-entity 10.0000.0000.0006.00
[PE4-LoopBack1]isis enable 1
[PE4-GigabitEthernet0/0/0]isis enable 1
2. 在MPLS骨干网上配置MPLS基本能力和MPLS LDP，建立LDP LSP
[PE1]mpls lsr-id 1.1.1.1
[PE1]mpls
[PE1]mpls ldp
[PE1-GigabitEthernet0/0/0]mpls
[PE1-GigabitEthernet0/0/0]mpls ldp
[P1]mpls lsr-id 2.2.2.2
[P1]mpls
[P1]mpls ldp
[P1-GigabitEthernet0/0/0]mpls
[P1-GigabitEthernet0/0/0]mpls ldp
[P1-GigabitEthernet0/0/1]mpls
[P1-GigabitEthernet0/0/1]mpls ldp
[PE3]mpls lsr-id 3.3.3.3
[PE3]mpls
[PE3]mpls ldp
[PE3-GigabitEthernet0/0/0]mpls
[PE3-GigabitEthernet0/0/0]mpls ldp
[PE2]mpls lsr-id 4.4.4.4
[PE2]mpls
[PE2]mpls ldp
[PE2-GigabitEthernet0/0/0]mpls
[PE2-GigabitEthernet0/0/0]mpls ldp
[P2]mpls lsr-id 5.5.5.5
[P2]mpls
[P2]mpls ldp
[P2-GigabitEthernet0/0/0]mpls
[P2-GigabitEthernet0/0/0]mpls ldp
[P2-GigabitEthernet0/0/1]mpls
[P2-GigabitEthernet0/0/1]mpls ldp
[PE4]mpls lsr-id 6.6.6.6
[PE4]mpls
[PE4]mpls ldp
[PE4-GigabitEthernet0/0/0]mpls
[PE4-GigabitEthernet0/0/0]mpls ldp
3. 在PE设备上配置VPN实例，将CE接入PE
[PE1]ip vpn-instance vpn1
[PE1-vpn-instance-vpn1]ipv4-family
[PE1-vpn-instance-vpn1-af-ipv4]route-distinguisher 100:1
[PE1-vpn-instance-vpn1-af-ipv4]vpn-target 1:1
[PE1-GigabitEthernet0/0/1]ip binding vpn-instance vpn1
[PE1-GigabitEthernet0/0/1]ip add 10.1.1.1 24
[PE3]ip vpn-instance vpn1
[PE3-vpn-instance-vpn1]ipv4-family
[PE3-vpn-instance-vpn1-af-ipv4]route-distinguisher 100:3
[PE3-vpn-instance-vpn1-af-ipv4]vpn-target 1:1
[PE3-GigabitEthernet0/0/1]ip binding vpn-instance vpn1
[PE3-GigabitEthernet0/0/1]ip add 10.3.1.3 24
[PE2]ip vpn-instance vpn1
[PE2-vpn-instance-vpn1]ipv4-family
[PE2-vpn-instance-vpn1-af-ipv4]route-distinguisher 100:2
[PE2-vpn-instance-vpn1-af-ipv4]vpn-target 1:1
[PE2-GigabitEthernet0/0/1]ip binding vpn-instance vpn1
[PE2-GigabitEthernet0/0/1]ip add 10.2.1.4 24
[PE4]ip vpn-instance vpn1
[PE4-vpn-instance-vpn1]ipv4-family
[PE4-vpn-instance-vpn1-af-ipv4]route-distinguisher 100:4
[PE4-vpn-instance-vpn1-af-ipv4]vpn-target 1:1
[PE4-GigabitEthernet0/0/1]ip binding vpn-instance vpn1
[PE4-GigabitEthernet0/0/1]ip add 10.4.1.6 24
4. 在PE之间建立MP-IBGP对等体关系
[PE1]bgp 100
[PE1-bgp]peer 3.3.3.3 as-number 100
[PE1-bgp]peer 3.3.3.3 connect-interface LoopBack 1
[PE1-bgp]ipv4-family vpnv4
[PE1-bgp-af-vpnv4]peer 3.3.3.3 enable
[PE3]bgp 100
[PE3-bgp]peer 1.1.1.1 as-number 100
[PE3-bgp]peer 1.1.1.1 connect-interface LoopBack 1
[PE3-bgp]ipv4-family vpnv4
[PE3-bgp-af-vpnv4]peer 1.1.1.1 enable
[PE2]bgp 100
[PE2-bgp]peer 6.6.6.6 as-number 100
[PE2-bgp]peer 6.6.6.6 connect-interface LoopBack 1
[PE2-bgp]ipv4-family vpnv4
[PE2-bgp-af-vpnv4]peer 6.6.6.6 enable
[PE4]bgp 100
[PE4-bgp]peer 4.4.4.4 as-number 100
[PE4-bgp]peer 4.4.4.4 connect-interface LoopBack 1
[PE4-bgp]ipv4-family vpnv4
[PE4-bgp-af-vpnv4]peer 4.4.4.4 enable
5. 在PE与CE之间配置EBGP路由协议，引入VPN路由
[CE1-GigabitEthernet0/0/0]ip add 10.1.1.7 24
[CE1-GigabitEthernet0/0/1]ip add 10.2.1.7 24
[CE1-GigabitEthernet0/0/2]ip ad 1.5.1.7 24
[CE1]bgp 65410
[CE1-bgp]peer 10.1.1.1 as-number 100
[CE1-bgp]peer 10.2.1.4 as-number 100
[CE1-bgp]import-route direct
[CE2-GigabitEthernet0/0/0]ip add 10.3.1.8 24
[CE2-GigabitEthernet0/0/1]ip add 10.4.1.8 24
[CE2-GigabitEthernet0/0/2]ip add 1.6.1.8 24
[CE2]bgp 65420
[CE2-bgp]peer 10.3.1.3 as-number 100
[CE2-bgp]peer 10.4.1.6 as-number 100
[CE2-bgp]import-route direct
[PE1]bgp 100
[PE1-bgp]ipv4-family vpn-instance vpn1
[PE1-bgp-vpn1]peer 10.1.1.7 as-number 65410
[PE1-bgp-vpn1]import-route direct
[PE2]bgp 100
[PE2-bgp]ipv4-family vpn-instance vpn1
[PE2-bgp-vpn1]peer 10.2.1.7 as-number 65410
[PE2-bgp-vpn1]import-route direct
PE3]bgp 100
[PE3-bgp]ipv4-family vpn-instance vpn1
[PE3-bgp-vpn1]peer 10.3.1.8 as-number 65420
[PE3-bgp-vpn1]import-route direct
[PE4]bgp 100
[PE4-bgp]ipv4-family vpn-instance vpn1
[PE4-bgp-vpn1]peer 10.4.1.8 as-number 65420
[PE4-bgp-vpn1]import-route direct
6. 在CE1上配置允许CE1到CE2的流量允许负载分担
[CE1]bgp 65410
[CE1-bgp]ipv4-family unicast
[CE1-bgp-af-ipv4]maximum load-balancing 2
7. 配置路由策略，增大PE3上发布给CE2的BGP路由的MED值，使CE2到CE1的流量流经PE4，PE3作为备份
[PE3]route-policy p1 permit node 10
[PE3-route-policy]apply cost 120
[PE3]bgp 100
[PE3-bgp]ipv4-family vpn-instance vpn1
[PE3-bgp-vpn1]peer 10.3.1.8 route-policy p1 export
发现对于到1.5.1.0/30的路由，PE3发布的MED值为120，比PE4发布的MED值大（缺省情况下MED的值为0），所以选择PE4发布的
8. 检查配置
看到去往对端CE2所接用户的路由，且是负载分担的
去往对端CE1所接用户的路由，且下一跳为10.4.1.6（PE4上接入CE2的接口IP地址）
