单域MPLS ***数据转发实验分析
MPLS ×××數據詳細轉發流程示意圖：
配置思路：
在自治系統AS100中配置IGP，使得兩臺PE路由器的lo 0接口路由可達；
兩臺PE路由器路由可達后，在兩臺PE路由器之間建立MP-iBGP鄰居關系，用來傳輸×××V4路由；
AS100中所有P路由器和PE路由器運行MPLS，并使用LDP來給非BGP路由分發標簽；
在PE路由器和CE路由器之間運行ospf路由協議，使得PE路由器的VRF路由表可以學習到CE路由器的路由；
將PE路由器VRF學習到的路由重分發進BGP，使得對端PE路由器可以通過MP-iBGP鄰居關系學習到×××V4路由；
將BGP路由在PE路由器上充分發進ce端ospf，使得CE路由器可以學習到相互的私有路由
上述拓撲基本配置
R1配置：
ip cef
!
ip vrf cisco
?rd100:1
?route-target export 100:2
?route-target import 100:2
!
mpls label range 100 199
mpls label protocol ldp
?
interface Loopback0
?ipaddress 1.1.1.1 255.255.255.255
!
interface Ethernet0/0
?ipvrf forwarding cisco
?ipaddress 10.1.15.1 255.255.255.0
?half-duplex
!
interface Ethernet0/1
?ipaddress 10.1.12.1 255.255.255.0
?half-duplex
?mplslabel protocol ldp
?mplsip
!????
router ospf 1 vrf cisco
?log-adjacency-changes
?redistribute bgp 100 subnets
?network 10.1.15.0 0.0.0.255 area 0
!
router ospf 100
?router-id 1.1.1.1
?log-adjacency-changes
?network 1.1.1.1 0.0.0.0 area 0
?network 10.1.12.0 0.0.0.255 area 0
!
router bgp 100
?bgprouter-id 1.1.1.1
?bgplog-neighbor-changes
?neighbor 4.4.4.4 remote-as 100
?neighbor 4.4.4.4 update-source Loopback0
?!
?address-family ipv4
?neighbor 4.4.4.4 activate
?noauto-summary
?nosynchronization
?exit-address-family
?!???????
?address-family ***v4
?neighbor 4.4.4.4 activate
?neighbor 4.4.4.4 send-community extended
?exit-address-family
?!
?address-family ipv4 vrf cisco
?redistribute ospf 1 vrf cisco match internalexternal 1 external 2
?nosynchronization
?exit-address-family
!
no ip http server
!
mpls ldp router-id Loopback0
?
R2配置：
ip cef
!
mpls label range 200 299
mpls label protocol ldp
!
interface Loopback0
?ipaddress 2.2.2.2 255.255.255.255
!
interface Ethernet0/0
?ipaddress 10.1.23.2 255.255.255.0
?half-duplex
?mplslabel protocol ldp
?mplsip
!
interface Ethernet0/1
?ipaddress 10.1.12.2 255.255.255.0
?half-duplex
?mplslabel protocol ldp
?mplsip
!
router ospf 100
?router-id 2.2.2.2
?log-adjacency-changes
?network 2.2.2.2 0.0.0.0 area 0
?network 10.1.12.0 0.0.0.255 area 0
?network 10.1.23.0 0.0.0.255 area 0
!
no ip http server
!
mpls ldp router-id Loopback0
?
R3配置：
ip cef
!
mpls label range 300 399
mpls label protocol ldp
!
interface Loopback0
?ipaddress 3.3.3.3 255.255.255.255
!
interface Ethernet0/0
?ipaddress 10.1.23.3 255.255.255.0
?half-duplex
?mplslabel protocol ldp
?mplsip
!
interface Ethernet0/1
?ipaddress 10.1.34.3 255.255.255.0
?half-duplex
?mplslabel protocol ldp
?mplsip
!
router ospf 100
?router-id 3.3.3.3
?log-adjacency-changes
?network 3.3.3.3 0.0.0.0 area 0
?network 10.1.23.0 0.0.0.255 area 0
?network 10.1.34.0 0.0.0.255 area 0
!
no ip http server
!
mpls ldp router-id Loopback0
?
R4配置：
ip cef
!
ip vrf cisco
?rd100:4
?route-target export 100:2
?route-target import 100:2
!
mpls label range 400 499
mpls label protocol ldp
!
interface Loopback0
?ipaddress 4.4.4.4 255.255.255.255
!
interface Ethernet0/0
?ipvrf forwarding cisco
?ip address10.1.46.4 255.255.255.0
?half-duplex
!
interface Ethernet0/1
?ipaddress 10.1.34.4 255.255.255.0
?half-duplex
?mplslabel protocol ldp
?mplsip
!????????
router ospf 1 vrf cisco
?log-adjacency-changes
?redistribute bgp 100 subnets
?network 10.1.46.0 0.0.0.255 area 0
!
router ospf 100
?router-id 4.4.4.4
?log-adjacency-changes
?network 4.4.4.4 0.0.0.0 area 0
?network 10.1.34.0 0.0.0.255 area 0
!
router bgp 100
?bgplog-neighbor-changes
?neighbor 1.1.1.1 remote-as 100
?neighbor 1.1.1.1 update-source Loopback0
?!
?address-family ipv4
?neighbor 1.1.1.1 activate
?noauto-summary
?nosynchronization
?exit-address-family
?!
?address-family ***v4
?neighbor 1.1.1.1 activate
?neighbor 1.1.1.1 send-community extended
?exit-address-family
?!
?address-family ipv4 vrf cisco
?redistribute ospf 1 vrf cisco match internalexternal 1 external 2
?nosynchronization
?exit-address-family
!
mpls ldp router-id Loopback0
?
R5配置：
ip cef
interface Loopback0
?ipaddress 5.5.5.5 255.255.255.255
!
interface Ethernet0/0
?ipaddress 10.1.15.5 255.255.255.0
?half-duplex
!
router ospf 1
?router-id 5.5.5.5
?log-adjacency-changes
?network 5.5.5.5 0.0.0.0 area 0
?network 10.1.15.0 0.0.0.255 area 0
?
R6配置：
ip cef
interface Loopback0
?ipaddress 6.6.6.6 255.255.255.255
!
interface Ethernet0/0
?ipaddress 10.1.46.6 255.255.255.0
?half-duplex
!
router ospf 1
?router-id 6.6.6.6
?log-adjacency-changes
?network 6.6.6.6 0.0.0.0 area 0
?network10.1.46.0 0.0.0.255 area 0
分析：
當R1和R4建立MP-iBG鄰居關系后，R1在將從VRF cisco中學習到的路由5.5.5.5/32發送給R4時將攜帶RD 100：1，并且分配標簽為106，如下：
R1#show?ip bgp? ***v4 rd 100:1 labels
??Network????????? Next Hop????? In label/Out label
RouteDistinguisher: 100:1(cisco)
?? 5.5.5.5/32?????? 10.1.15.5?????? 106/nolabel
R4#SHOw?ip bgp? ***v4? rd 100:1 labels
??Network????????? Next Hop????? In label/Out label
Route Distinguisher: 100:1
?? 5.5.5.5/32?????? 1.1.1.1???????? nolabel/106
注意：BGP只會為每一個×××V4前綴分配一個標簽，這個標簽用來說明報文的下一跳是誰，也就是說如果×××V4在MP-BGP傳輸的過程中，如果×××V4前綴的下一跳不發生變化，那么途徑的BGP路由器將沒有權利修改標簽。
?
以下是MP-iBGP在***v4路由更新時的調試信息：
*Mar 1 00:06:27.167: ***:bgp_***v4_alloc_tag route_tag_change for cisco:5.5.5.5/255.255.255.255
*Mar? 1 00:06:27.167: ***:tag_***_find_route_tags: 100:1:5.5.5.5
*Mar? 1 00:06:27.171: ***:intag=106, outtag=unknown, outtag owner=BGP
?
*Mar?1 00:04:29.171: ***: bgp_***v4_bnetinit: 100:4:6.6.6.6/32
*Mar?1 00:04:29.175: BGP: Accepted path from 4.4.4.4
*Mar? 1 00:04:42.131: ***:bgp_***v4_bnetinit: 100:1:6.6.6.6/32
*Mar? 1 00:04:42.283: ***:tag_***_find_route_tags: 100:1:6.6.6.6
*Mar? 1 00:04:42.287: ***:intag=***-route, outtag=405, outtag owner=BGP
可以看到R1學習到的100:4:6.6.6.6的outlable標簽為405，是R4所分配
R1給前綴100:1:5.5.5.5，分配的in lable 標簽為106
?
在R5上查看，可以看到R5已經學習到了6.6.6.6/32的路由信息，R6同理會學到5.5.5.5/32的路由
R5#show?ip route
Codes: C - connected, S - static, R - RIP,M - mobile, B - BGP
??????D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
??????N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
??????E1 - OSPF external type 1, E2 - OSPF external type 2
??????i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
??????ia - IS-IS inter area, * - candidate default, U - per-user static route
??????o - ODR, P - periodic downloaded static route
?
Gateway of last resort is not set
?
????5.0.0.0/32 is subnetted, 1 subnets
C??????5.5.5.5 is directly connected, Loopback0
????6.0.0.0/32 is subnetted, 1 subnets
O IA??? 6.6.6.6 [110/21] via10.1.15.1, 00:13:02, Ethernet0/0
????10.0.0.0/24 is subnetted, 2 subnets
C??????10.1.15.0 is directly connected, Ethernet0/0
O IA???10.1.46.0 [110/11] via 10.1.15.1, 00:13:02, Ethernet0/0
你會發現從MP-iBGP重分發進入的路由是域間路由標識IA，原因如下：
為OSPF工作的BGP擴展屬性使得OSPF路由可以完全的在遠端PE路由器上重建，路由類型讓遠端PE路由器了解到什么類型的路由在OSPF中通告。如果是類型1和2或者3的話，遠程PE路由器將會通告一條域間匯總路由到OSPF中。
?
在PE路由器R1上查看VRF路由表：
R1#show ?ip route ?vrf cisco
Routing Table: cisco
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
? ? ? ?D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area?
? ? ? ?N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
? ? ? ?E1 - OSPF external type 1, E2 - OSPF external type 2
? ? ? ?i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
? ? ? ?ia - IS-IS inter area, * - candidate default, U - per-user static route
? ? ? ?o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
? ? ?5.0.0.0/32 is subnetted, 1 subnets
O ? ? ? 5.5.5.5 [110/11] via 10.1.15.5, 00:55:43, Ethernet0/0
? ? ?6.0.0.0/32 is subnetted, 1 subnets
B ? ? ? 6.6.6.6 [200/11] via 4.4.4.4, 00:57:23
? ? ?10.0.0.0/24 is subnetted, 2 subnets
C ? ? ? 10.1.15.0 is directly connected, Ethernet0/0
B ? ? ? 10.1.46.0 [200/0] via 4.4.4.4, 00:57:23
可以看到去往6.6.6.6/32的路由為BGP路由，并且下一跳為4.4.4.4
查看6.6.6.6的*** 標簽：
R1#show ip bgp ?***v4 ?rd 100:4 LAbels?
? ?Network ? ? ? ? ?Next Hop ? ? ?In label/Out label
Route Distinguisher: 100:4
? ?6.6.6.6/32 ? ? ? 4.4.4.4 ? ? ? ? nolabel/405
可以看到6.6.6.6的*** outlable標簽為405，當數據在進入VRF cisco后將添加底部標簽405
查看4.4.4.4的LDP標簽
R1#show ?mpls ?forwarding-table?
Local ?Outgoing ? ?Prefix ? ? ? ? ? ?Bytes tag ?Outgoing ? Next Hop ? ?
tag ? ?tag or VC ? or Tunnel Id ? ? ?switched ? interface ? ? ? ? ? ? ?
100 ? ?Pop tag ? ? 10.1.23.0/24 ? ? ?0 ? ? ? ? ?Et0/1 ? ? ?10.1.12.2 ? ?
101 ? ?203 ? ? ? ? 10.1.34.0/24 ? ? ?0 ? ? ? ? ?Et0/1 ? ? ?10.1.12.2 ? ?
102 ? ?Pop tag ? ? 2.2.2.2/32 ? ? ? ?0 ? ? ? ? ?Et0/1 ? ? ?10.1.12.2 ? ?
103 ? ?201 ? ? ? ? 3.3.3.3/32 ? ? ? ?0 ? ? ? ? ?Et0/1 ? ? ?10.1.12.2 ? ?
104 ? ?202 ? ? ? ? 4.4.4.4/32 ? ? ? ?0 ? ? ? ? ?Et0/1 ? ? ?10.1.12.2 ? ?
105 ? ?Aggregate ? 10.1.15.0/24[V] ? 0 ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
106 ? ?Untagged ? ?5.5.5.5/32[V] ? ? 570 ? ? ? ?Et0/0 ? ? ?10.1.15.5
在加入底部標簽405后將數據將會壓入遞歸查詢到的下一跳4.4.4.4的出站標簽202，
在P路由器R2上查看路由表：
R2#show ip route
Codes: C - connected, S - static, R - RIP,M - mobile, B - BGP
??????D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
??????N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
??????E1 - OSPF external type 1, E2 - OSPF external type 2
??????i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
??????ia - IS-IS inter area, * - candidate default, U - per-user static route
??????o - ODR, P - periodic downloaded static route
?
Gateway of last resort is not set
?
????1.0.0.0/32 is subnetted, 1 subnets
O??????1.1.1.1 [110/11] via 10.1.12.1, 00:13:16, Ethernet0/1
????2.0.0.0/32 is subnetted, 1 subnets
C??????2.2.2.2 is directly connected, Loopback0
????3.0.0.0/32 is subnetted, 1 subnets
O??????3.3.3.3 [110/11] via 10.1.23.3, 00:13:16, Ethernet0/0
????4.0.0.0/32 is subnetted, 1 subnets
O??????4.4.4.4 [110/21] via 10.1.23.3, 00:13:16, Ethernet0/0
????10.0.0.0/24 is subnetted, 3 subnets
C??????10.1.12.0 is directly connected, Ethernet0/1
C??????10.1.23.0 is directly connected, Ethernet0/0
O??????10.1.34.0 [110/20] via 10.1.23.3, 00:13:17, Ethernet0/0
可以看到R2上不存在5.5.5.5和6.6.6.6的路由信息，所以在AS100中用戶數據的轉發只能靠標簽轉發來完成，二不是IP路由轉發
查看R2的標簽轉發信息庫，如下：
R2#show mpls? forwarding-table
Local?Outgoing??? Prefix??????????? Bytes tag? Outgoing??Next Hop???
tag???tag or VC?? or Tunnel Id????? switched??interface?????????????
200???Pop tag???? 1.1.1.1/32??????? 14931????? Et0/1?????10.1.12.1???
201???Pop tag???? 3.3.3.3/32??????? 0 ?????????Et0/0????? 10.1.23.3???
202???302???????? 4.4.4.4/32??????? 19345????? Et0/0?????10.1.23.3???
203???Pop tag???? 10.1.34.0/24????? 0?????????Et0/0????? 10.1.23.3???
可以看到R2對于路由4.4.4.4的本地標簽為202，遠程標簽為302，在數據進入p路由器R2后，將完全按照標簽進行轉發，而不是路由轉發，從而實現通信。
Ping測試：
R5#ping 6.6.6.6 source? 5.5.5.5
?
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6,timeout is 2 seconds:
Packet sent with a source address of5.5.5.5
!!!!!
Success rate is 100 percent (5/5),round-trip min/avg/max = 56/91/112 ms
可以看到沒有問題，能夠通信
轉載于:https://blog.51cto.com/4719076/1538227
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