MPLS ××× 網絡中的OSPF Sham-Link

時間 2020-01-24

原文原文鏈接

實驗拓撲圖redis

實驗描述：如上圖所示，現PE-R一、P-R二、PE-R3爲MPLS ×××網絡，兩CE客戶須要經過MPLS ×××骨幹網絡進行通訊，而且CE-R4與CE-R6之間有一條鏈路做爲備份鏈路，正常狀況要，R4至R6的流量經過MPLS ×××網絡走，當MPLS ×××網絡存在故障時，經過R4與R6之間的互聯鏈路走，下面配置OSPF Sham-Link實現上述要求。網絡

一、首先配置MP-BGP，MPLS，VRF，PE與CE的OSPF路由協議ide

PE-R1的配置：oop

R1#show runn測試

ip vrf Maoui

rd 100:10spa

route-target export 100:10router

route-target import 100:11blog

!接口

ip cef

mpls label range 100 199

interface Loopback0

ip address 1.1.1.1 255.255.255.255

interface FastEthernet0/0

ip vrf forwarding Mao

ip address 14.1.1.1 255.255.255.252

interface FastEthernet1/0

ip address 12.1.1.1 255.255.255.252

mpls ip

router ospf 2 vrf Mao

redistribute bgp 100 subnets

network 14.1.1.0 0.0.0.3 area 1

router ospf 1

router-id 1.1.1.1

network 1.1.1.1 0.0.0.0 area 0

network 12.1.1.0 0.0.0.3 area 0

router bgp 100

bgp log-neighbor-changes

no bgp default ipv4-unicast

neighbor 3.3.3.3 remote-as 100

neighbor 3.3.3.3 update-source Loopback0

address-family ***v4

neighbor 3.3.3.3 activate

neighbor 3.3.3.3 send-community extended

exit-address-family

address-family ipv4 vrf Mao

redistribute ospf 2 match internal external 1 external 2

exit-address-family

P-R2配置：

ip cef

mpls label range 200 299

interface Loopback0

ip address 2.2.2.2 255.255.255.255

interface FastEthernet0/0

ip address 12.1.1.2 255.255.255.252

mpls ip

interface FastEthernet0/1

ip address 23.1.1.1 255.255.255.252

mpls ip

router ospf 1

router-id 2.2.2.2

network 2.2.2.2 0.0.0.0 area 0

network 12.1.1.0 0.0.0.3 area 0

network 23.1.1.0 0.0.0.3 area 0

PE-R3配置：

R3#show runn

ip vrf Mao

rd 100:10

route-target export 100:11

route-target import 100:10

ip cef

mpls label range 300 399

interface Loopback0

ip address 3.3.3.3 255.255.255.255

interface FastEthernet0/0

ip address 23.1.1.2 255.255.255.252

mpls ip

interface FastEthernet0/1

ip vrf forwarding Mao

ip address 36.1.1.1 255.255.255.252

router ospf 2 vrf Mao

redistribute bgp 100 subnets

network 36.1.1.0 0.0.0.3 area 1

router ospf 1

router-id 3.3.3.3

network 3.3.3.3 0.0.0.0 area 0

network 23.1.1.0 0.0.0.3 area 0

router bgp 100

bgp log-neighbor-changes

no bgp default ipv4-unicast

neighbor 1.1.1.1 remote-as 100

neighbor 1.1.1.1 update-source Loopback0

address-family ***v4

neighbor 1.1.1.1 activate

neighbor 1.1.1.1 send-community extended

exit-address-family

address-family ipv4 vrf Mao

redistribute ospf 2 match internal external 1 external 2

exit-address-family

CE-R4的配置：

interface Loopback0

ip address 4.4.4.4 255.255.255.255

interface FastEthernet0/0

ip address 14.1.1.2 255.255.255.252

interface FastEthernet0/1

ip address 46.1.1.1 255.255.255.252

router ospf 10

router-id 4.4.4.4

network 4.4.4.4 0.0.0.0 area 1

network 14.1.1.0 0.0.0.3 area 1

network 46.1.1.0 0.0.0.3 area 1

CE-R6的配置：

interface Loopback0

ip address 6.6.6.6 255.255.255.255

interface FastEthernet0/0

ip address 36.1.1.2 255.255.255.252

interface FastEthernet0/1

ip address 46.1.1.2 255.255.255.252

router ospf 2

router-id 6.6.6.6

network 6.6.6.6 0.0.0.0 area 1

network 36.1.1.0 0.0.0.3 area 1

network 46.1.1.0 0.0.0.3 area 1

二、CE端路由狀況分析

查看CE端路由狀況

R4#show ip route

4.0.0.0/32 is subnetted, 1 subnets

C 4.4.4.4 is directly connected, Loopback0

6.0.0.0/32 is subnetted, 1 subnets

O 6.6.6.6 [110/2] via 46.1.1.2, 00:10:24, FastEthernet0/1

14.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 14.1.1.0/30 is directly connected, FastEthernet0/0

L 14.1.1.2/32 is directly connected, FastEthernet0/0

36.0.0.0/30 is subnetted, 1 subnets

O 36.1.1.0 [110/2] via 46.1.1.2, 00:10:24, FastEthernet0/1

46.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 46.1.1.0/30 is directly connected, FastEthernet0/1

L 46.1.1.1/32 is directly connected, FastEthernet0/1

從CE-R4看到6.6.6.6路由爲區域內路由，是因爲CE-R4與CE-R6之間互聯的線路運行OSPF，而且在區域1中，而從MPLS ×××骨幹網絡中傳過來的6.6.6.6路由爲區域間路由；而OSPF的選路原則是區域內路由優於區域間路由；

在PE-R1上查看×××V4路由，也能夠看到6.6.6.6的路由，下一跳指向的是CE-R4，以下：

R1#show ip bgp ***v4 all

Network Next Hop Metric LocPrf Weight Path

Route Distinguisher: 100:10 (default for vrf Mao)

* i 4.4.4.4/32 3.3.3.3 3 100 0 ?

*> 14.1.1.2 2 32768 ?

*> 6.6.6.6/32 14.1.1.2 3 32768 ?

* i 3.3.3.3 2 100 0 ?

* i 14.1.1.0/30 3.3.3.3 3 100 0 ?

*> 0.0.0.0 0 32768 ?

*> 36.1.1.0/30 14.1.1.2 3 32768 ?

* i 3.3.3.3 0 100 0 ?

*> 46.1.1.0/30 14.1.1.2 2 32768 ?

* i 3.3.3.3 2 100 0 ?

R1#show ip route vrf Mao

4.0.0.0/32 is subnetted, 1 subnets

O 4.4.4.4 [110/2] via 14.1.1.2, 00:40:39, FastEthernet0/0

6.0.0.0/32 is subnetted, 1 subnets

O 6.6.6.6 [110/3] via 14.1.1.2, 00:23:00, FastEthernet0/0

14.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 14.1.1.0/30 is directly connected, FastEthernet0/0

L 14.1.1.1/32 is directly connected, FastEthernet0/0

36.0.0.0/30 is subnetted, 1 subnets

O 36.1.1.0 [110/3] via 14.1.1.2, 00:23:00, FastEthernet0/0

46.0.0.0/30 is subnetted, 1 subnets

O 46.1.1.0 [110/2] via 14.1.1.2, 00:23:00, FastEthernet0/0

當將CE-R4與CE-R6互聯的線路shutdown後，查看R4的路由以下：

R4(config)#int fa0/1

R4(config-if)#shutdown

R4#show ip route

4.0.0.0/32 is subnetted, 1 subnets

C 4.4.4.4 is directly connected, Loopback0

6.0.0.0/32 is subnetted, 1 subnets

O IA 6.6.6.6 [110/3] via 14.1.1.1, 00:00:52, FastEthernet0/0

14.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 14.1.1.0/30 is directly connected, FastEthernet0/0

L 14.1.1.2/32 is directly connected, FastEthernet0/0

36.0.0.0/30 is subnetted, 1 subnets

O IA 36.1.1.0 [110/2] via 14.1.1.1, 00:00:52, FastEthernet0/0

46.0.0.0/30 is subnetted, 1 subnets

O IA 46.1.1.0 [110/3] via 14.1.1.1, 00:00:52, FastEthernet0/0

如今看到的路由是區域間路由，是PE-R1傳過來的，爲實現網絡的可靠性，正常狀況下，R4與R6之間的鏈路是備份線路，平時數據經過MPLS ×××傳遞，爲實現上述R4路由輸出狀況，如今在PE路由器之間配置Sham-Link實現兩CE端平常數據經過MPLS ×××網絡傳遞，當MPLS ×××網絡出現故障時，數據流量切換至R4與R6的互聯線路，以便不影響兩CE端的互訪。

三、Sham-Link配置

R1(config)#int loo 11 //用於創建OSPF Sham-Link

R1(config-if)#ip vrf forwarding Mao

R1(config-if)#ip add 11.1.1.1 255.255.255.255

R1(config)#router bgp 100

R1(config-router)#address-family ipv4 vrf Mao

R1(config-router-af)#network 11.1.1.1 mask 255.255.255.255 //將其發佈至MP-BGP中

R1(config)#router ospf 2 vrf Mao

R1(config-router)#area 1 sham-link 11.1.1.1 33.1.1.1 cost 5 //建立sham-link

R3(config)#int loo 33

R3(config-if)#ip vrf forwarding Mao

R3(config-if)#ip add 33.1.1.1 255.255.255.255

R3(config)#router bgp 100

R3(config-router)#address-family ipv4 vrf Mao

R3(config-router-af)#network 33.1.1.1 mask 255.255.255.255

R3(config)#router ospf 2 vrf Mao

R3(config-router)#area 1 sham-link 33.1.1.1 11.1.1.1 cost 5

查看其鄰居是否創建成功，可用show ip ospf neighbor或者show ip ospf sham-link

R3#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface

2.2.2.2 1 FULL/BDR 00:00:36 23.1.1.1 FastEthernet0/0

14.1.1.1 0 FULL/ - 00:00:30 11.1.1.1 OSPF_SL0

6.6.6.6 1 FULL/DR 00:00:36 36.1.1.2 FastEthernet0/1

R3#show ip ospf sham-links

Sham Link OSPF_SL0 to address 11.1.1.1 is up

Area 1 source address 33.1.1.1

Run as demand circuit

DoNotAge LSA allowed. Cost of using 5 State POINT_TO_POINT,

Timer intervals configured, Hello 10, Dead 40, Wait 40,

Hello due in 00:00:04

Adjacency State FULL (Hello suppressed)

Index 2/2, retransmission queue length 0, number of retransmission 0

First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)

Last retransmission scan length is 0, maximum is 0

Last retransmission scan time is 0 msec, maximum is 0 msec

四、Sham-link配置分析及結果分析

上面sham-link的配置設置了cost值爲5，那麼PE-PE之間這條sham-link的開銷值就爲5，此時查看R4上的路由，6.6.6.6的路由下一跳仍是直接指向R6，並無走MPLS ×××網絡。

R4#show ip route

4.0.0.0/32 is subnetted, 1 subnets

C 4.4.4.4 is directly connected, Loopback0

6.0.0.0/32 is subnetted, 1 subnets

O 6.6.6.6 [110/2] via 46.1.1.2, 00:13:09, FastEthernet0/1

11.0.0.0/32 is subnetted, 1 subnets

O E2 11.1.1.1 [110/1] via 14.1.1.1, 00:10:07, FastEthernet0/0

14.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 14.1.1.0/30 is directly connected, FastEthernet0/0

L 14.1.1.2/32 is directly connected, FastEthernet0/0

33.0.0.0/32 is subnetted, 1 subnets

O E2 33.1.1.1 [110/1] via 14.1.1.1, 00:09:31, FastEthernet0/0

36.0.0.0/30 is subnetted, 1 subnets

O 36.1.1.0 [110/2] via 46.1.1.2, 00:13:09, FastEthernet0/1

46.0.0.0/8 is variably subnetted, 2 subnets, 2 masks

C 46.1.1.0/30 is directly connected, FastEthernet0/1

L 46.1.1.1/32 is directly connected, FastEthernet0/1

查看R1上的bgp ***v4 6.6.6.6的路由狀況

R1#show ip bgp ***v4 all 6.6.6.6

BGP routing table entry for 100:10:6.6.6.6/32, version 43

Paths: (2 available, best #1, table Mao)

Advertised to update-groups:

Refresh Epoch 1

Local

14.1.1.2 from 0.0.0.0 (1.1.1.1) //來至CE-R4，而且是最優

Origin incomplete, metric 3, localpref 100, weight 32768, valid, sourced, best

Extended Community: RT:100:10 OSPF DOMAIN ID:0x0005:0x000000020200

OSPF RT:0.0.0.1:2:0 OSPF ROUTER ID:14.1.1.1:0

mpls labels in/out 108/nolabel

rx pathid: 0, tx pathid: 0x0

Refresh Epoch 1

Local

3.3.3.3 (metric 3) from 3.3.3.3 (3.3.3.3) //來至PE-R3，不是最優的

Origin incomplete, metric 2, localpref 100, valid, internal //metric 爲2

Extended Community: RT:100:11 OSPF DOMAIN ID:0x0005:0x000000020200

OSPF RT:0.0.0.1:2:0 OSPF ROUTER ID:36.1.1.1:0

mpls labels in/out 108/307

rx pathid: 0, tx pathid: 0

從上述路由輸出分析可知，R6直接傳給R4（之間互聯線路）的6.6.6.6的路由，其OSPF開銷值爲2；而從MPLS ×××網絡經PE-R3傳至PE-R1的6.6.6.6路由的開銷值爲2，若是傳遞至R4，那麼開銷值爲8（5+2+1），其值大於R6直接傳給R4的開銷值，所以R6直接傳給R4的6.6.6.6的路由將會加入路由表項，所以在R4的路由表中將會看到6.6.6.6的下一跳仍是指向46.1.1.2。

要想實現兩CE端互訪經過MPLS ×××網絡，能夠修改COST值來實現，現修改R4與R6互聯接口的ospf cost值；

R4(config)#int fa0/1

R4(config-if)#ip ospf cost 10 將其cost值設置大於經過MPLS ×××的cost值

R6(config)#int fa0/1

R6(config-if)#ip ospf cost 10

如今R4上查看路由表狀況

R4#show ip route

4.0.0.0/32 is subnetted, 1 subnets

C 4.4.4.4 is directly connected, Loopback0

6.0.0.0/32 is subnetted, 1 subnets

O 6.6.6.6 [110/8] via 14.1.1.1, 00:25:30, FastEthernet0/0 //下一跳指向PE-R1

11.0.0.0/32 is subnetted, 1 subnets