场景描述：as 100和as 300模拟两家公司的自治域系统，现因业务合作需求，两公司需要建设mpls ***实现私网互访，as 567和as 8910模拟ISP，要求ar1 lo0口172.16.1
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场景描述：
as 100和as 300模拟两家公司的自治域系统，现因业务合作需求，两公司需要建设mpls ***实现私网互访，as 567和as 8910模拟ISP，要求ar1 lo0口172.16.1.1和ar3 lo0口172.16.3.3通信。（ar2和ar4同需求）
各广播域网段和地址如图，isp路由器lo0地址以序号编号，如R5 lo0地址为5.5.5.5/32，R6-R10同理；R1-R4 lo0地址分别为172.16.1.1/32，172.16.2.2/32，172.16.3.3/32,172.16.4.4/32.
一、isp内部igp互通
1.1、配置所有设备ip地址，如图（具体步骤略）
1.2、isp内建立ospf邻居，宣告环回口
R5：ospf 1 router-id 5.5.5.5 area 0.0.0.0 network 5.5.5.5 0.0.0.0 network 56.1.1.5 0.0.0.0 R6：ospf 1 router-id 6.6.6.6 area 0.0.0.0 network 6.6.6.6 0.0.0.0 network 56.1.1.6 0.0.0.0 network 67.1.1.6 0.0.0.0 R7：ospf 1 router-id 7.7.7.7 area 0.0.0.0 network 7.7.7.7 0.0.0.0 network 67.1.1.7 0.0.0.0 R8：ospf 1 router-id 8.8.8.8 area 0.0.0.0 network 8.8.8.8 0.0.0.0 network 89.1.1.8 0.0.0.0 R9：ospf 1 router-id 9.9.9.9 area 0.0.0.0 network 9.9.9.9 0.0.0.0 network 89.1.1.9 0.0.0.0 network 91.1.1.9 0.0.0.0R10：ospf 1 router-id 10.10.10.10 area 0.0.0.0 network 10.10.10.10 0.0.0.0 network 91.1.1.10 0.0.0.0 查看是否已成功建立ospf邻居：
二、isp内部建立mpls隧道，使用ldp自动分发标签，解决将来的路由黑洞
R5：mpls lsr-id 5.5.5.5mplsinterface GigabitEthernet0/0/1 mpls mpls ldpR6：mpls lsr-id 6.6.6.6mplsmpls ldpinterface GigabitEthernet0/0/1 mpls mpls ldpinterface GigabitEthernet0/0/0 mpls mpls ldpR7：mpls lsr-id 7.7.7.7mplsmpls ldpinterface GigabitEthernet0/0/0 mpls mpls ldpR8：mpls lsr-id 8.8.8.8mplsmpls ldpinterface GigabitEthernet0/0/1 mpls mpls ldpR9：mpls lsr-id 9.9.9.9mplsmpls ldpinterface GigabitEthernet0/0/1 mpls mpls ldpinterface GigabitEthernet0/0/0 mpls mpls ldpR10：mpls lsr-id 10.10.10.10mplsmpls ldpinterface GigabitEthernet0/0/0 mpls mpls ldp查看ldp邻居是否成功建立：
[R6]dis mpls ldp peer LDP Peer Information in Public network A '*' before a peer means the peer is being deleted. ------------------------------------------------------------------------------ PeerID TransportAddress DiscoverySource ------------------------------------------------------------------------------ 5.5.5.5:0 5.5.5.5 GigabitEthernet0/0/0 7.7.7.7:0 7.7.7.7 GigabitEthernet0/0/1 ------------------------------------------------------------------------------ TOTAL: 2 Peer(s) Found.[R6][R8]dis mpls ldp peer LDP Peer Information in Public network A '*' before a peer means the peer is being deleted. ------------------------------------------------------------------------------ PeerID TransportAddress DiscoverySource ------------------------------------------------------------------------------ 9.9.9.9:0 9.9.9.9 GigabitEthernet0/0/1 ------------------------------------------------------------------------------ TOTAL: 1 Peer(s) Found.[R8]三、PE设备建立v4邻居，用于将来传递路由
R5：bgp 567 undo default ipv4-unicast peer 7.7.7.7 as-number 567 peer 7.7.7.7 connect-interface LoopBack0 ipv4-family unicast undo synchronization undo peer 7.7.7.7 enable ipv4-family ***v4 policy ***-target peer 7.7.7.7 enableR7：bgp 567 undo default ipv4-unicast peer 5.5.5.5 as-number 567 peer 5.5.5.5 connect-interface LoopBack0 ipv4-family unicast undo synchronization undo peer 5.5.5.5 enable ipv4-family ***v4 policy ***-target peer 5.5.5.5 enableR8：bgp 8910 undo default ipv4-unicast peer 10.10.10.10 as-number 8910 peer 10.10.10.10 connect-interface LoopBack0 ipv4-family unicast undo synchronization undo peer 10.10.10.10 enable ipv4-family ***v4 policy ***-target peer 10.10.10.10 enableR10：bgp 8910 undo default ipv4-unicast peer 8.8.8.8 as-number 8910 peer 8.8.8.8 connect-interface LoopBack0 ipv4-family unicast undo synchronization undo peer 8.8.8.8 enable ipv4-family ***v4 policy ***-target peer 8.8.8.8 enable查看***v4邻居是否正常建立：
[R7]dis bgp ***v4 al pe BGP local router ID : 7.7.7.7 Local AS number : 567 Total number of peers : 1 Peers in established state : 1 Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv 5.5.5.5 4 567 7 7 0 00:05:29 Established 0[R7][R10]dis bgp ***v4 al pe BGP local router ID : 10.10.10.10 Local AS number : 8910 Total number of peers : 1 Peers in established state : 1 Peer V AS MsgRcvd MsgSent OutQ Up/Down State PrefRcv 8.8.8.8 4 8910 2 2 0 00:00:46 Established 0[R10]四、建立CE与PE设备的连接
4.1、PE设备上创建vrf实例
R5：ip ***-instance 15 ipv4-family route-distinguisher 15:15 ***-target 57:5 export-extcommunity ***-target 57:7 import-extcommunityip ***-instance 25 ipv4-family route-distinguisher 25:25 ***-target 75:5 export-extcommunity ***-target 75:7 import-extcommunityR7：ip ***-instance 17 ipv4-family route-distinguisher 17:17 ***-target 57:7 export-extcommunity ***-target 57:5 import-extcommunityip ***-instance 27 ipv4-family route-distinguisher 27:27 ***-target 75:7 export-extcommunity ***-target 75:5 import-extcommunityR8：ip ***-instance 38 ipv4-family route-distinguisher 38:38 ***-target 810:8 export-extcommunity ***-target 810:10 import-extcommunityip ***-instance 48 ipv4-family route-distinguisher 48:48 ***-target 108:8 export-extcommunity ***-target 108:10 import-extcommunityR10：ip ***-instance 310 ipv4-family route-distinguisher 310:310 ***-target 810:10 export-extcommunity ***-target 810:8 import-extcommunityip ***-instance 410 ipv4-family route-distinguisher 410:410 ***-target 108:10 export-extcommunity ***-target 108:8 import-extcommunity4.2、PE设备接口绑定vrf实例R5：interface GigabitEthernet0/0/0 ip binding ***-instance 15 ip address 15.1.1.5 255.255.255.0 interface GigabitEthernet0/0/2 ip binding ***-instance 25 ip address 25.1.1.5 255.255.255.0 R10：interface GigabitEthernet0/0/1 ip binding ***-instance 310 ip address 31.1.1.10 255.255.255.0 interface GigabitEthernet0/0/2 ip binding ***-instance 410 ip address 41.1.1.10 255.255.255.0 4.3、PE与CE建立bgp ipv4邻居关系
R5：bgp 567 ipv4-family ***-instance 15 peer 15.1.1.1 as-number 100 ipv4-family ***-instance 25 peer 25.1.1.2 as-number 200 R1：bgp 100 peer 15.1.1.5 as-number 567 ipv4-family unicast undo synchronization peer 15.1.1.5 enableR2：bgp 200 peer 25.1.1.5 as-number 567 ipv4-family unicast undo synchronization peer 25.1.1.5 enableR10：bgp 8910 ipv4-family ***-instance 310 peer 31.1.1.3 as-number 300 ipv4-family ***-instance 410 peer 41.1.1.4 as-number 400 R3：bgp 300 peer 31.1.1.10 as-number 8910 ipv4-family unicast undo synchronization peer 31.1.1.10 enableR4：bgp 400 peer 41.1.1.10 as-number 8910 ipv4-family unicast undo synchronization peer 41.1.1.10 enable查看是否成功建立ipv4邻居关系：
五、使用子接口，建立asbr的bgp连接
R7：interface GigabitEthernet0/0/1.13 dot1q termination vid 13 ip binding ***-instance 17 ip address 192.168.78.7 255.255.255.0 arp broadcast enableinterface GigabitEthernet0/0/1.24 dot1q termination vid 24 ip binding ***-instance 27 ip address 192.168.78.7 255.255.255.0 arp broadcast enablebgp 567 ipv4-family ***-instance 17 peer 192.168.78.8 as-number 8910 ipv4-family ***-instance 27 peer 192.168.78.8 as-number 8910 R8：interface GigabitEthernet0/0/0.13 dot1q termination vid 13 ip binding ***-instance 38 ip address 192.168.78.8 255.255.255.0 arp broadcast enableinterface GigabitEthernet0/0/0.24 dot1q termination vid 24 ip binding ***-instance 48 ip address 192.168.78.8 255.255.255.0 arp broadcast enablebgp 8910 ipv4-family ***-instance 38 peer 192.168.78.7 as-number 567 ipv4-family ***-instance 48 peer 192.168.78.7 as-number 567六、在CE设备上用bgp宣告路由
R1：bgp 100network 172.16.1.1 255.255.255.255R2：bgp 200network 172.16.2.2 255.255.255.255R3：bgp 300network 172.16.3.3 255.255.255.255R4：bgp 400network 172.16.4.4 255.255.255.255七、测试
八、注意点
8.1、PE设备连接CE时，除了用bgp外，也可以用ospf、isis等igp协议，但这样做的话就必须在PE、CE设备上都执行双向引入；
8.2、mpls lsr-id 路由必须可达，且需要是32位路由，因为ldp默认只为32位路由分配标签；
九、数据通信分析
9.1、路由传递路径分析
R1使用bgp传递lo0路由172.16.1.1/32给R5，172.16.1.1/32通过R5的g/0/0/0口进入vrf 15，路由被打上RD变成96位的v4路由，因为R5和R7位mp-bgp邻居且出入RT值匹配，所以R7可以接收R5传来的172.16.1.1/32的路由并进入R7的vrf 17(此路由携带内网标签)；R7的g0/0/1.13绑定vrf 17，右半部分的所有设备被R7当做vrf 17的CE，所以R7会把接收到的路由172.16.1.1/32进入vrf 17后的ipv4路由传递给R8；R8也把左半边设备当做CE，所以172.16.1.1/32会进入vrf 38并打上RD变成路由，再根据RT出入值发送给R10(此路由携带内网标签)；R10收到1.1.1.1/32后加入vrf 310并把ipv4路由发送给bgp邻居R3，R3至此收到了172.16.1.1/32.
9.2、数据流量分析
R3查看全局路由表，发送目的地址为172.16.1.1的数据包给31.1.1.10；R10查看-instance 310，在ip层下压入内网标签(用于告诉R8该查哪张路由表)，再压入外网标签(用于解决as8910的路由黑洞)；数据包到达R8后查找-instance 38路由表进入R7；R7查找-instance 17路由表并压入内网、外网标签，到达R5；R5查找-instance 15路由表转发给R1.
十、优缺点
优点：原理简单，便于理解，只是将ASBR所连接的另一个AS当做CE，然后通过子接口建立BGP邻居
缺点：配置过程繁琐，在需要建立多个通道的时候，ASBR上创建的子接口会很多；且ASBR需要维护路由，有违背MPLS ***路由传递按照CE1-PE1-PE2-CE2路线的理念。
