BGP/MPLS VPN OptionC（PE-PE）跨域研究实验

原创

wangbaoping1 2018-03-21 17:23:30 ©著作权

文章标签 BGP MPLS VPN 文章分类 网络安全

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1、实验环境以华为模拟器eNSP为实验环境，结合wireshark抓包进行BGP/MPLS ××× OptionA 控制层面、数据层面以及日常排错三个方面进行研究；如下图所示：

2、配置流程 1）配置IGP与公网MPLS LDP隧道: ① ISP1 PE1： router id 1.1.1.1 ospf 1 area 0.0.0.0 network 1.1.1.1 0.0.0.0 network 12.12.12.0 0.0.0.255 mpls lsr-id 1.1.1.1 mpls mpls ldp interface LoopBack0 ip address 1.1.1.1 255.255.255.255 mpls mpls ldp interface GigabitEthernet0/0/0 ip address 12.12.12.1 255.255.255.0 mpls mpls ldp P1： router id 2.2.2.2 ospf 1 area 0.0.0.0 network 2.2.2.2 0.0.0.0 network 12.12.12.0 0.0.0.255 network 23.23.23.0 0.0.0.255 mpls lsr-id 2.2.2.2 mpls mpls ldp ip address 2.2.2.2 255.255.255.255 mpls mpls ldp interface GigabitEthernet0/0/0 ip address 12.12.12.2 255.255.255.0 mpls mpls ldp interface GigabitEthernet0/0/1 ip address 23.23.23.2 255.255.255.0 mpls mpls ldp ASBR1： router id 3.3.3.3 ospf 1 area 0.0.0.0 network 3.3.3.3 0.0.0.0 network 23.23.23.0 0.0.0.255 mpls lsr-id 3.3.3.3 mpls mpls ldp ip address 3.3.3.3 255.255.255.255 mpls mpls ldp interface GigabitEthernet0/0/1 ip address 23.23.23.3 255.255.255.0 mpls mpls ldp 查看公网路有： <ASBR1>dis ip routing-table protocol ospf Route Flags: R - relay, D - download to fib

Public routing table : OSPF Destinations : 3 Routes : 3

OSPF routing table status : <Active> Destinations : 3 Routes : 3

Destination/Mask Proto Pre Cost Flags NextHop Interface

    1.1.1.1/32  OSPF    10   2           D   23.23.23.2      GigabitEthernet

0/0/1 2.2.2.2/32 OSPF 10 1 D 23.23.23.2 GigabitEthernet 0/0/1 12.12.12.0/24 OSPF 10 2 D 23.23.23.2 GigabitEthernet 0/0/1

OSPF routing table status : <Inactive> Destinations : 0 Routes : 0 查看MPLS LDP session: <ASBR1>dis mpls ldp session

LDP Session(s) in Public Network Codes: LAM(Label Advertisement Mode), SsnAge Unit(DDDD:HH:MM) A '*' before a session means the session is being deleted.

PeerID Status LAM SsnRole SsnAge KASent/Rcv

2.2.2.2:0 Operational DU Active 0000:00:18 75/75

TOTAL: 1 session(s) Found. 查看MPLS LSP： <ASBR1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
1.1.1.1/32 NULL/1024 -/GE0/0/1
1.1.1.1/32 1024/1024 -/GE0/0/1
2.2.2.2/32 NULL/3 -/GE0/0/1
2.2.2.2/32 1025/3 -/GE0/0/1
3.3.3.3/32 3/NULL -/-
②ISP2 PE2： router id 6.6.6.6 ospf 2 area 0.0.0.0 network 6.6.6.6 0.0.0.0 network 56.56.56.0 0.0.0.255 mpls lsr-id 6.6.6.6 mpls mpls ldp interface LoopBack0 ip address 6.6.6.6 255.255.255.255 mpls mpls ldp interface GigabitEthernet0/0/0 ip address 56.56.56.6 255.255.255.0 mpls mpls ldp P2： router id 5.5.5.5 ospf 2 area 0.0.0.0 network 5.5.5.5 0.0.0.0 network 56.56.56.0 0.0.0.255 network 45.45.45.0 0.0.0.255 mpls lsr-id 5.5.5.5 mpls mpls ldp ip address 5.5.5.5 255.255.255.255 mpls mpls ldp interface GigabitEthernet0/0/0 ip address 56.56.56.5 255.255.255.0 mpls mpls ldp interface GigabitEthernet0/0/1 ip address 45.45.45.5 255.255.255.0 mpls mpls ldp ASBR2： router id 4.4.4.4 ospf 2 area 0.0.0.0 network 4.4.4.4 0.0.0.0 network 45.45.45.0 0.0.0.255 mpls lsr-id 4.4.4.4 mpls mpls ldp ip address 4.4.4.4 255.255.255.255 mpls mpls ldp interface GigabitEthernet0/0/1 ip address 45.45.45.4 255.255.255.0 mpls mpls ldp 查看公网路有： <ASBR2>dis ip routing-table protocol ospf Route Flags: R - relay, D - download to fib

Public routing table : OSPF Destinations : 3 Routes : 3

OSPF routing table status : <Active> Destinations : 3 Routes : 3

Destination/Mask Proto Pre Cost Flags NextHop Interface

    5.5.5.5/32  OSPF    10   1           D   45.45.45.5      GigabitEthernet

0/0/1 6.6.6.6/32 OSPF 10 2 D 45.45.45.5 GigabitEthernet 0/0/1 56.56.56.0/24 OSPF 10 2 D 45.45.45.5 GigabitEthernet 0/0/1

OSPF routing table status : <Inactive> Destinations : 0 Routes : 0 查看MPLS LDP session: <ASBR2>dis mpls ldp session

LDP Session(s) in Public Network Codes: LAM(Label Advertisement Mode), SsnAge Unit(DDDD:HH:MM) A '*' before a session means the session is being deleted.

PeerID Status LAM SsnRole SsnAge KASent/Rcv

5.5.5.5:0 Operational DU Passive 0000:00:24 100/100

TOTAL: 1 session(s) Found. 查看MPLS LSP： <ASBR2>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
4.4.4.4/32 3/NULL -/-
5.5.5.5/32 NULL/3 -/GE0/0/1
5.5.5.5/32 1024/3 -/GE0/0/1
6.6.6.6/32 NULL/1025 -/GE0/0/1
6.6.6.6/32 1025/1025 -/GE0/0/1
2）配置各个站点CE与PE的×××实例: ①ISP1： PE1： ip vpn-instance spi ipv4-family route-distinguisher 100:1 vpn-target 100:1 export-extcommunity vpn-target 100:1 import-extcommunity interface GigabitEthernet0/0/1 ip binding vpn-instance spi ip address 192.168.1.254 255.255.255.0 ip vpn-instance spd ipv4-family route-distinguisher 200:1 vpn-target 200:1 export-extcommunity vpn-target 200:1 import-extcommunity interface GigabitEthernet0/0/2 ip binding vpn-instance spd ip address 10.10.1.254 255.255.255.0 ping测试站点到网关 ②ISP2 PE2： ip vpn-instance spi ipv4-family route-distinguisher 100:1 vpn-target 100:1 export-extcommunity vpn-target 100:1 import-extcommunity interface GigabitEthernet0/0/1 ip binding vpn-instance spi ip address 192.168.2.254 255.255.255.0 ip vpn-instance spd ipv4-family route-distinguisher 200:1 vpn-target 200:1 export-extcommunity vpn-target 200:1 import-extcommunity interface GigabitEthernet0/0/2 ip binding vpn-instance spd ip address 10.10.2.254 255.255.255.0 ping测试站点到网关 3）配置MP-EBGP在ISP1 PE1与ISP2 PE2 之间传递×××V4站点×××V4私网路由： ①想要ISP1的PE1与ISP2的PE2建立BGP peer，需要PE1的1.1.1.1 环回口与PE2的6.6.6.6首先三层路由相通； ASBR1： bgp 100 undo default ipv4-unicast peer 34.34.34.4 as-number 200

ipv4-family unicast undo synchronization import-route ospf 1（正常只需要把ospf学到的1.1.1.1导入BGP） peer 34.34.34.4 enable

ASBR2： [ASBR2]dis ip routing-table protocol bgp Route Flags: R - relay, D - download to fib

Public routing table : BGP Destinations : 5 Routes : 5

BGP routing table status : <Active> Destinations : 5 Routes : 5

Destination/Mask Proto Pre Cost Flags NextHop Interface

    1.1.1.1/32  EBGP    255  2           D   34.34.34.3      GigabitEthernet

0/0/0 ASBR2： [ASBR2]dis current-configuration configuration ospf ospf 2 import-route bgp（正常把MP-EBGP学到的1.1.1.1导入就行） area 0.0.0.0 network 4.4.4.4 0.0.0.0 network 45.45.45.0 0.0.0.255

bgp 200 undo default ipv4-unicast peer 34.34.34.3 as-number 100 ipv4-family unicast undo synchronization import-route ospf 2（把ospf学到的6.6.6.6导入MP-EBGP）） peer 34.34.34.3 enable ASBR1： <ASBR1>dis current-configuration configuration ospf ospf 1 import-route bgp（把MP-EBGP学到的6.6.6.6导入OSPF1） area 0.0.0.0 network 3.3.3.3 0.0.0.0 network 23.23.23.0 0.0.0.255 PE1上ping PE1的6.6.6.6： <PE1>ping -a 1.1.1.1 6.6.6.6 PING 6.6.6.6: 56 data bytes, press CTRL_C to break Reply from 6.6.6.6: bytes=56 Sequence=1 ttl=251 time=70 ms Reply from 6.6.6.6: bytes=56 Sequence=2 ttl=251 time=40 ms Reply from 6.6.6.6: bytes=56 Sequence=3 ttl=251 time=40 ms Reply from 6.6.6.6: bytes=56 Sequence=4 ttl=251 time=50 ms Reply from 6.6.6.6: bytes=56 Sequence=5 ttl=251 time=30 ms

--- 6.6.6.6 ping statistics --- 5 packet(s) transmitted 5 packet(s) received 0.00% packet loss round-trip min/avg/max = 30/46/70 ms ②想要ISP1的PE1与ISP2的PE2私网路由想通，PE1的1.1.1.1与PE2的6.6.6.6的公网LSP隧道要通；在PE1查看6.6.6.6 MPLS的公网标签分配情况： <PE1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
2.2.2.2/32 NULL/3 -/GE0/0/0
2.2.2.2/32 1024/3 -/GE0/0/0
3.3.3.3/32 NULL/1024 -/GE0/0/0
3.3.3.3/32 1025/1024 -/GE0/0/0
1.1.1.1/32 3/NULL -/-
<PE1>dis fib 6.6.6.6 Route Entry Count: 1 Destination/Mask Nexthop Flag TimeStamp Interface TunnelID 6.6.6.6/32 12.12.12.2 DGHU t[2451] GE0/0/0 0x0 在FIB表中包括Destination、Mask、Nexthop、Flag、TimeStamp、Interface和TunnelID字段，其中Destination、Mask、Nexthop、Interface字段是与IP路由表的对应字段一样，其他3个字段说明： ①Flag：转发表项的标志，可能是G、H、U、S、D、B、L中一个或多字母组合。 ●G（Gateway网关路由）：表示下一跳是网关。 ●H（Host主机路由）：表示该路由为主机路由。 ●U（Up可用路由）：表示该路由状态是Up。 ●S（Static静态路由）：表示该路由为手动配置路由。 ●D（Dynamic 动态路由）：表示该路由为根据路由算法自动生成路由。 ●B（Black Hole 黑洞路由）：表示下一跳是空接口。 ●L（Vlink Route）：表示Vlink类型路由 ②TimeStamp：转发表项的时间戳，表示该表项已存在的时间，单位是s。 ③TunnelID：表示转发表项索引。该值不为0时，表示匹配该项的报文通过对应的隧道进行转发。该值为0时，表示报文不通过隧道转发。

<PE1>dis fib 3.3.3.3 Route Entry Count: 1 Destination/Mask Nexthop Flag TimeStamp Interface TunnelID 3.3.3.3/32 12.12.12.2 DGHU t[56] GE0/0/0 0x3 P1：<P1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
1.1.1.1/32 NULL/3 -/GE0/0/0
1.1.1.1/32 1026/3 -/GE0/0/0
2.2.2.2/32 3/NULL -/-
3.3.3.3/32 NULL/3 -/GE0/0/1
3.3.3.3/32 1027/3 -/GE0/0/1
<P1>dis fib 6.6.6.6 Route Entry Count: 1 Destination/Mask Nexthop Flag TimeStamp Interface TunnelID 6.6.6.6/32 23.23.23.3 DGHU t[6087] GE0/0/1 0x0 ASBR1：<ASBR1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
1.1.1.1/32 NULL/1026 -/GE0/0/1
1.1.1.1/32 1030/1026 -/GE0/0/1
2.2.2.2/32 NULL/3 -/GE0/0/1
2.2.2.2/32 1031/3 -/GE0/0/1
3.3.3.3/32 3/NULL -/-
ASBR2 IPV4 MP-EBGP不会给公网6.6.6.6 路由分发标签； ASBR2与ASBR1 IPV4 MP-EBGP默认路由默认不会携带标签； [ASBR2]dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
5.5.5.5/32 NULL/3 -/GE0/0/1
5.5.5.5/32 1030/3 -/GE0/0/1
4.4.4.4/32 3/NULL -/-
6.6.6.6/32 NULL/1027 -/GE0/0/1
6.6.6.6/32 1031/1027 -/GE0/0/1
<ASBR1>dis bgp ip routing-table label ASBR2上配置：配置ASBR2把6.6.6.6 发给ASBR1时分配标签: 并配置ASBR2与ASBR1 IPV4-MP-EBGP有携带路由标签的能力： [ASBR2]route-policy label permit node 10 apply mpls-label bgp 200 peer 34.34.34.3 as-number 100 ipv4-family unicast undo synchronization import-route ospf 2 peer 34.34.34.3 enable peer 34.34.34.3 route-policy label export peer 34.34.34.3 label-route-capability

ASBR1s上也配置IPv4的MP-BGP有有携带路由标签的能力： bgp 100 peer 34.34.34.4 as-number 200 ipv4-family unicast undo synchronization import-route ospf 1 peer 34.34.34.4 enable peer 34.34.34.4 label-route-capability

此时在ASBR1上查看发现ASBR2 在把6.6.6.6公网路由传给ASBR1时已经分发了标签并且可以在IPV4-MP-EBGP上携带： [ASBR1]dis bgp routing-table label

BGP Local router ID is 3.3.3.3 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 5

    Network           NextHop           In/Out Label

> 4.4.4.4 34.34.34.4 NULL/1036 > 5.5.5.5 34.34.34.4 NULL/1033 > 6.6.6.6 34.34.34.4 NULL/1035 > 45.45.45.0 34.34.34.4 NULL/1032 *> 56.56.56.0 34.34.34.4 NULL/1034 ASBR2 IPV4-MP-EBGP给6.6.6.6分配了1035的标签 <P1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
1.1.1.1/32 NULL/3 -/GE0/0/0
1.1.1.1/32 1026/3 -/GE0/0/0
2.2.2.2/32 3/NULL -/-
3.3.3.3/32 NULL/3 -/GE0/0/1
3.3.3.3/32 1027/3 -/GE0/0/1
但是P1上发现ASBR1的LDP无法给从ASBR2 通过IPV4-MP-EBGP的学到6.6.6.6路由分配标签； ASBR1上LDP默认也不会给BGP路由分发标签 ASBR1上配置： [ASBR1-mpls]lsp-trigger bgp-label-route lsp-trigger bgp-label-route命令都用于配置LDP LSP的触发建立策略；（仅适用于带标签的公网BGP路由）此时查看P1： <P1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
1.1.1.1/32 NULL/3 -/GE0/0/0
1.1.1.1/32 1026/3 -/GE0/0/0
2.2.2.2/32 3/NULL -/-
3.3.3.3/32 NULL/3 -/GE0/0/1
3.3.3.3/32 1027/3 -/GE0/0/1
4.4.4.4/32 NULL/1035 -/GE0/0/1
4.4.4.4/32 1031/1035 -/GE0/0/1
6.6.6.6/32 NULL/1036 -/GE0/0/1
6.6.6.6/32 1032/1036 -/GE0/0/1
5.5.5.5/32 NULL/1037 -/GE0/0/1
5.5.5.5/32 1033/1037 -/GE0/0/1
ASBR1上的LDP给6.6.6.6分配了1032的标签；同理对于1.1.1.1路由也是如此，配置ASBR1与ASBR2公网MP-EBGP可以携带有标签路由，应用策略使得IPV4-MP-EBGP给各种传递的路由分发MPLS label ASBR上查看：ASBR1 MP-EBGP（IPV4单播）给1.1.1.1分发1040标签 <ASBR2>dis bgp routing-table label

BGP Local router ID is 4.4.4.4 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 10

    Network           NextHop           In/Out Label

> 1.1.1.1 34.34.34.3 NULL/1040 > 2.2.2.2 34.34.34.3 NULL/1038 > 3.3.3.3 34.34.34.3 NULL/1042 > 4.4.4.4 127.0.0.1 1036/NULL > 5.5.5.5 45.45.45.5 1033/NULL > 6.6.6.6 45.45.45.5 1035/NULL > 12.12.12.0 34.34.34.3 NULL/1039 > 23.23.23.0 34.34.34.3 NULL/1041 > 45.45.45.0 45.45.45.4 1032/NULL > 56.56.56.0 45.45.45.5 1034/NULL 同理ASBR2上配置MPLS 使得LDP可以给BGP路由打上MPLS标签； P2上查看：配置lsp-trigger bgp-label-route之前： <P2>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
5.5.5.5/32 3/NULL -/-
4.4.4.4/32 NULL/3 -/GE0/0/1
4.4.4.4/32 1026/3 -/GE0/0/1
6.6.6.6/32 NULL/3 -/GE0/0/0
6.6.6.6/32 1027/3 -/GE0/0/0
配置lsp-trigger bgp-label-route之后：ASBR2 LDP给1.1.1.1分发的1032的标签 <P2>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
5.5.5.5/32 3/NULL -/-
4.4.4.4/32 NULL/3 -/GE0/0/1
4.4.4.4/32 1026/3 -/GE0/0/1
6.6.6.6/32 NULL/3 -/GE0/0/0
6.6.6.6/32 1027/3 -/GE0/0/0
3.3.3.3/32 NULL/1040 -/GE0/0/1
3.3.3.3/32 1031/1040 -/GE0/0/1
1.1.1.1/32 NULL/1041 -/GE0/0/1
1.1.1.1/32 1032/1041 -/GE0/0/1
2.2.2.2/32 NULL/1042 -/GE0/0/1
2.2.2.2/32 1033/1042 -/GE0/0/1
PE1上测试：

<PE1>ping -c 1000 -a 1.1.1.1 6.6.6.6 <PE1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name

6.6.6.6/32 NULL/1032 -/GE0/0/0
6.6.6.6/32 1034？/1032 -/GE0/0/0
<P1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/1036 -/GE0/0/1
6.6.6.6/32 1032/1036 -/GE0/0/1
<ASBR1>dis mpls lsp

             LSP Information: BGP  LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/1035 -/-

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 1036/1035 -/-
<ASBR1>dis bgp routing-table label

BGP Local router ID is 3.3.3.3 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 10

    Network           NextHop           In/Out Label

*> 6.6.6.6 34.34.34.4 NULL/1035 <ASBR2>dis bgp routing-table label

BGP Local router ID is 4.4.4.4 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 10

    Network           NextHop           In/Out Label

*> 6.6.6.6 45.45.45.5 1035/NULL <ASBR2>dis mpls lsp

             LSP Information: BGP  LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 1035/NULL -/-

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/1027 -/GE0/0/1
6.6.6.6/32 1031？/1027 -/GE0/0/1
<P2>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/3 -/GE0/0/0
6.6.6.6/32 1027/3 -/GE0/0/0
<PE2>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name

6.6.6.6/32 3/NULL -/-
抓包： PE1 出口： P1出口：

ASBR1出口：

ASBR2出口： P2出口：

注意在ASBR2上关于6.6.6.6路由标签分发上： <ASBR2>dis mpls lsp

             LSP Information: BGP  LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 1035/NULL -/-

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 1031/1027 -/GE0/0/1
LDP给6.6.6.6分发的1031标签，IPv4-MP-BGP ASBR1给6.6.6.6分发的1035标签；1031的标签不会随路由传给ASBR1； PE1与PE2正式开始配置×××V4的MP-EBGP路由： PE1： bgp 100 undo default ipv4-unicast peer 6.6.6.6 as-number 200 peer 6.6.6.6 ebgp-max-hop 255 peer 6.6.6.6 connect-interface LoopBack0

ipv4-family unicast undo synchronization undo peer 6.6.6.6 enable

ipv4-family vpnv4 policy vpn-target peer 6.6.6.6 enable

ipv4-family vpn-instance spd network 10.10.1.0 255.255.255.0

ipv4-family vpn-instance spi network 192.168.1.0 PE2： bgp 200 undo default ipv4-unicast peer 1.1.1.1 as-number 100 peer 1.1.1.1 ebgp-max-hop 255 peer 1.1.1.1 connect-interface LoopBack0

ipv4-family unicast undo synchronization undo peer 1.1.1.1 enable

ipv4-family vpnv4 policy vpn-target peer 1.1.1.1 enable

ipv4-family vpn-instance spd network 10.10.2.0 255.255.255.0

ipv4-family vpn-instance spi network 192.168.2.0 3、控制层面分析 1）CE3的路由192.168.2.0/24传递给CE1过程： ①PE2上连接CE3直连路由： <PE2>dis ip routing-table vpn-instance spi protocol direct Route Flags: R - relay, D - download to fib

spi routing table : Direct Destinations : 4 Routes : 4

Direct routing table status : <Active> Destinations : 4 Routes : 4

Destination/Mask Proto Pre Cost Flags NextHop Interface

192.168.2.0/24  Direct  0    0           D   192.168.2.254   GigabitEthernet

0/0/1 192.168.2.254/32 Direct 0 0 D 127.0.0.1 GigabitEthernet 0/0/1 192.168.2.255/32 Direct 0 0 D 127.0.0.1 GigabitEthernet 0/0/1 255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0

Direct routing table status : <Inactive> Destinations : 0 Routes : 0 <PE2>dis ip routing-table vpn-instance spi verbose Destination: 192.168.2.0/24 Protocol: Direct Process ID: 0 Preference: 0 Cost: 0 NextHop: 192.168.2.254 Neighbour: 0.0.0.0 State: Active Adv Age: 03h29m00s Tag: 0 Priority: high Label: NULL QoSInfo: 0x0 IndirectID: 0x0
RelayNextHop: 0.0.0.0 Interface: GigabitEthernet0/0/1 TunnelID: 0x0 Flags: D

②把vpn spi中192.168.2.0直连路由导入MP-BGP中： <PE2>dis current-configuration configuration bgp [V200R003C00] bgp 200 undo default ipv4-unicast peer 4.4.4.4 as-number 200 peer 4.4.4.4 connect-interface LoopBack0 ipv4-family unicast undo synchronization peer 4.4.4.4 enable ipv4-family vpnv4 policy vpn-target peer 4.4.4.4 enable ipv4-family vpn-instance spi network 192.168.2.0 ③PE2 在MP-BGP中192.168.2.0/24路由情况： <PE2>dis bgp vpnv4 vpn-instance spi routing-table label

BGP Local router ID is 6.6.6.6 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete Total number of routes from all PE: 5 Route Distinguisher: 100:1 Network NextHop In/Out Label *> 192.168.2.0 192.168.2.254 1037/NULL <PE2>dis bgp vpnv4 vpn-instance spi routing-table 192.168.2.0

BGP local router ID : 6.6.6.6 Local AS number : 200

×××-Instance spi, Router ID 6.6.6.6: Paths: 1 available, 1 best, 1 select BGP routing table entry information of 192.168.2.0/24: Network route. From: 0.0.0.0 (0.0.0.0) Route Duration: 02h05m43s
Direct Out-interface: GigabitEthernet0/0/1 Original nexthop: 192.168.2.254 Qos information : 0x0 AS-path Nil, origin igp, MED 0, pref-val 0, valid, local, best, select, pre 0 Not advertised to any peer yet PE2上的MP-BGP给192.168.2.0的×××v4路由分配的私网标签： <PE2>dis bgp vpnv4 all routing-table label

BGP Local router ID is 6.6.6.6 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total number of routes from all PE: 4

Route Distinguisher: 100:1 Network NextHop In/Out Label

*>i 192.168.1.0 4.4.4.4 NULL/1029 *> 192.168.2.0 192.168.2.254 1037/NULL ④PE1 在MP-BGP中收到192.168.2.0/24路由情况： PE1上收到PE2 MP-EBGP 192.168.2.0 的×××V4路由分的标签1037 <PE1>dis bgp vpnv4 all routing-table label BGP Local router ID is 1.1.1.1 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total number of routes from all PE: 4

Route Distinguisher: 100:1 Network NextHop In/Out Label *> 192.168.2.0 6.6.6.6 NULL/1037 PE1到PE2 6.6.6.6的公网MPLS标签： <PE1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name

6.6.6.6/32 NULL/1032 -/GE0/0/0
6.6.6.6/32 1034？/1032 -/GE0/0/0
<P1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/1036 -/GE0/0/1
6.6.6.6/32 1032/1036 -/GE0/0/1
<ASBR1>dis mpls lsp

             LSP Information: BGP  LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/1035 -/-

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 1036/1035 -/-
<ASBR1>dis bgp routing-table label

BGP Local router ID is 3.3.3.3 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 10

    Network           NextHop           In/Out Label

*> 6.6.6.6 34.34.34.4 NULL/1035 <ASBR2>dis bgp routing-table label

BGP Local router ID is 4.4.4.4 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 10

    Network           NextHop           In/Out Label

*> 6.6.6.6 45.45.45.5 1035/NULL <ASBR2>dis mpls lsp

             LSP Information: BGP  LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 1035/NULL -/-

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/1027 -/GE0/0/1
6.6.6.6/32 1031？/1027 -/GE0/0/1
<P2>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/3 -/GE0/0/0
6.6.6.6/32 1027/3 -/GE0/0/0
<PE2>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name

6.6.6.6/32 3/NULL -/-

PE1上到6.6.6.6的FIB表： <PE1>dis fib 6.6.6.6 Route Entry Count: 1 Destination/Mask Nexthop Flag TimeStamp Interface TunnelID 6.6.6.6/32 12.12.12.2 DGHU t[12828] GE0/0/0 0x11

4、数据层面分析 1）CE1到CE3的192.168.2.1数据转发分析： ① PC1 192.168.1.1 到网关PE1上的192.168.1.254； ② 在PE1上查询spi vpn实例的路由表查到到192.168.2.0 下一跳为6.6.6.6;私网标签为1037； ③ 路由迭代，查找到路由如下： <PE1>dis ip routing-table 6.6.6.6 Route Flags: R - relay, D - download to fib

Routing Table : Public Summary Count : 1 Destination/Mask Proto Pre Cost Flags NextHop Interface 6.6.6.6/32 O_ASE 150 1 D 12.12.12.2 GigabitEthernet0/0/0 <PE1>dis fib 6.6.6.6 Route Entry Count: 1 Destination/Mask Nexthop Flag TimeStamp Interface TunnelID 6.6.6.6/32 12.12.12.2 DGHU t[12828] GE0/0/0 0x11 ④MPLS ldp 为 6.6.6.6/32路由分配的公网标签为1032： <PE1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name

6.6.6.6/32 NULL/1032 -/GE0/0/0
6.6.6.6/32 1034？/1032 -/GE0/0/0
⑤ 去往192.168.2.1的数据包在PE1上G0/0/0封装如图所示; PE1的G0/0/0上使能了MPLS，所以进行MPLS2.5层标签转发； ⑥ 在P1上查看标签路径： <P1>dis fib 6.6.6.6 Route Entry Count: 1 Destination/Mask Nexthop Flag TimeStamp Interface TunnelID 6.6.6.6/32 23.23.23.3 DGHU t[12853] GE0/0/1 0x11 <P1>dis mpls lsp

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 NULL/1036 -/GE0/0/1
6.6.6.6/32 1032/1036 -/GE0/0/1
在P1离开接口G0/0/1上抓包发现只留公网标签1036私网标签1037： ⑦ 在ASBR1上BGP路由中发现路由6.6.6.6公网标签（ASBR2 IPV4-MP-EBGP分发）为1035：

BGP Local router ID is 3.3.3.3 Status codes: * - valid, > - best, d - damped, h - history, i - internal, s - suppressed, S - Stale Origin : i - IGP, e - EGP, ? - incomplete

Total Number of Routes: 10

    Network           NextHop           In/Out Label

*> 6.6.6.6 34.34.34.4 NULL/1035 离开ASBR1截图： ⑧注意在ASBR2上关于6.6.6.6路由标签分发上： <ASBR2>dis mpls lsp

             LSP Information: BGP  LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 1035/NULL -/-

             LSP Information: LDP LSP

FEC In/Out Label In/Out IF Vrf Name
6.6.6.6/32 1031/1027 -/GE0/0/1
LDP给6.6.6.6分发的1031标签，IPv4-MP-BGP ASBR1给6.6.6.6分发的1035标签；1031的标签不会随路由传给ASBR1；离开ASBR2：一直×××V4私网标签不变；公网标签不断变化； ⑨、通过路由表到PC3主机： Ping的截图：

注意：Option C ISP-PE之间跨域主要解决： 1、 PE之间三层路由连通性；2.5层公网LSP连通性； 2、为了三层路由ASBR1与ASBR2之间公网MP-EBGP连接；公网没有携带与分发MPLS标签能力； 3、 LDP默认在ASBR上不给BGP路由分发标签，哪它不会传给P设备任何关于PE环回地址的标签情况。

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