配置Sham-Link 时，需要满足以下条件：
＊在PE 上单独创建/3 2 位的地址，在PE 之间使用这个地址来建立 Sham-Link 。
＊这个／32位地址的接口必须放入相应的VRF。
＊这个／32位地址必须在B GP 里发布，而不能在OSPF里发布。
注：Sham-Link 是有COST值的，PE 穿越MPLS ×××骨干网络的OSPF CO ST值，就是Sham-Link 的CO ST值，如果没有后门链路，Sham-Link 就不需要创建了 。
说明: 在上图中，CE 路由器R3和R4上分别有地址33.3.3.3和44.4.4.4，配置 Sham-Link使PE 路由器到达远程场点地址从MPLS ×××骨干网络中传输。
1．配置R1与R2的路由协议为RIP-sh run 配置
R1#sh run | s r r
router rip
version 2
network 1.0.0.0
network 10.0.0.0
no auto-summary
R2#sh run | s r r
router rip
version 2
network 2.0.0.0
network 10.0.0.0
no auto-summary
2．在R1与R2上配置MPLS
R1
ip cef
mpls label range 100 199
mpls label protocol ldp
mpls ldp router-id lo0 force
interface Ethernet1/0
ip address 10.1.12.1 255.255.255.0
mpls ip
R2
ip cef
mpls label range 200 299
mpls label protocol ldp
mpls ldp router-id lo0 force
interface Ethernet1/1
ip address 10.1.12.2 255.255.255.0
mpls ip
3.配置MPLS ×××
R1#sh run | s ip vrf
ip vrf vpn1
rd 1:100
route-target export 1:100
route-target import 1:100
R1(config)#int e1/1
R1(config -i f)#ip vrf forwarding vpn1
R2#sh run | s ip vrf
ip vrf vpn1
rd 1:100
route-target export 1:100
route-target import 1:100
R2(config)#int e1/0
R2(config -i f)#ip vrf forwarding vpn1
4．配置OSPF
R1#sh run | s r o
router ospf 1 vrf vpn1
router-id 1.1.1.1
network 1.1.1.0 0.0.0.255 area 1
network 10.1.13.0 0.0.0.255 area 1
R2#sh run | s r o
router ospf 1 vrf vpn1
router-id 2.2.2.2
network 2.2.2.0 0.0.0.255 area 1
network 10.1.24.0 0.0.0.255 area 1
R3#sh run | s r o
router ospf 1
router-id 3.3.3.3
network 3.3.3.0 0.0.0.255 area 1
network 10.1.13.0 0.0.0.255 area 1
network 10.1.34.0 0.0.0.255 area 1
network 33.3.3.3 0.0.0.0 area 1
R4#sh run | s r o
router ospf 1
router-id 4.4.4.4
network 4.4.4.0 0.0.0.255 area 1
network 10.1.24.0 0.0.0.255 area 1
network 10.1.34.0 0.0.0.255 area 1
network 44.4.4.4 0.0.0.0 area 1
5.配置MP-BGP
R1#sh run | s r b
router bgp 12
bgp router-id 1.1.1.1
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 12
neighbor 2.2.2.2 update-source Loopback0
!
address-family vpnv4
neighbor 2.2.2.2 activate
neighbor 2.2.2.2 send-community extended
exit-address-family
!
address-family ipv4 vrf vpn1
network 100.1.1.1 mask 255.255.255.255
redistribute ospf 1
exit-address-family
R2#sh run | s r b
router bgp 12
bgp router-id 2.2.2.2
bgp log-neighbor-changes
neighbor 1.1.1.1 remote-as 12
neighbor 1.1.1.1 update-source Loopback0
!
address-family vpnv4
neighbor 1.1.1.1 activate
neighbor 1.1.1.1 send-community extended
exit-address-family
!
address-family ipv4 vrf vpn1
network 200.1.1.1 mask 255.255.255.255
redistribute ospf 1
exit-address-family
6.查看路由
(1)查看PE路由器R1 bgp的路由
R1#sh ip bgp vpnv4 all
BGP table version is 8, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale, m multipath, b backup-path, x best-external, f RT-Filter, a additional-path
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1:100 (default for vrf vpn1)
* i3.3.3.3/32 2.2.2.2 21 100 0 ?
*> 10.1.13.3 11 32768 ?
* i4.4.4.4/32 2.2.2.2 11 100 0 ?
*> 10.1.13.3 21 32768 ?
* i10.1.13.0/24 2.2.2.2 30 100 0 ?
*> 0.0.0.0 0 32768 ?
* i10.1.24.0/24 2.2.2.2 0 100 0 ?
*> 10.1.13.3 30 32768 ?
* i10.1.34.0/24 2.2.2.2 20 100 0 ?
*> 10.1.13.3 20 32768 ?
* i33.3.3.3/32 2.2.2.2 21 100 0 ?
*> 10.1.13.3 11 32768 ?
* i44.4.4.4/32 2.2.2.2 11 100 0 ?
*> 10.1.13.3 21 32768 ?
说明: PE路由器 R1到达 33.3.3.3和44.4.4.4都从 CE路由器 R3走。
(２)查看PE路由器R1 vrf的路由
R1#sh ip route vrf vpn1
Routing Table: vpn1
Codes: L - local, 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, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/11] via 10.1.13.3, 00:15:24, Ethernet1/1
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/21] via 10.1.13.3, 00:07:17, Ethernet1/1
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C 10.1.13.0/24 is directly connected, Ethernet1/1
L 10.1.13.1/32 is directly connected, Ethernet1/1
O 10.1.24.0/24 [110/30] via 10.1.13.3, 00:07:17, Ethernet1/1
O 10.1.34.0/24 [110/20] via 10.1.13.3, 00:07:17, Ethernet1/1
33.0.0.0/32 is subnetted, 1 subnets
O 33.3.3.3 [110/11] via 10.1.13.3, 00:08:04, Ethernet1/1
44.0.0.0/32 is subnetted, 1 subnets
O 44.4.4.4 [110/21] via 10.1.13.3, 00:07:17, Ethernet1/1
说明: PE路由器 R1到达 33.3.3.3和44.4.4.4都从 CE路由器 R3走。
7.在PE路由器之间创建Sham-Link
(1)在PE路由器上创建/32 位loopback地址
R1#sh run int l100
interface Loopback100
ip vrf forwarding vpn1 -------在配置完此命令后，地址会消失，需要重新配置IP。
ip address 100.1.1.1 255.255.255.255
end
说明: 创建的/32 位地址必须放入 VRF。
R2#sh run int l100
interface Loopback100
ip vrf forwarding vpn1
ip address 200.1.1.1 255.255.255.255
说明: 创建的/32 位地址必须放入 VRF。
(2)将/32 位地址在MP-BGP 里发布
R1(config)#router bg 12
R1(config-router)#address-family ipv4 vrf vpn1
R1(config-router-af)#network 100.1.1.1 mask 255.255.255.255
R2(config)#router bg 12
R2(config-router)#address-family ipv4 vrf vpn1
R2(config-router-af)#network 200.1.1.1 mask 255.255.255.255
(3) 创建Sham-Link
R1(config)#router ospf 2 vrf vpn1
r1(config-router)#area 1 sham-link 100.1.1.1 200.1.1.1 cost 10
说明: 创建Sham-Link 时，要指定源地址和目的地址，并且指明COST 值。
R2:
R2(config)#router ospf 1 vrf vpn1
R2(config-router)#area 1 sham-link 200.1.1.1 100.1.1.1 cost 10
说明: 创建Sham-Link 时，要指定源地址和目的地址，并且指明COST 值。
8．查看结果
(1)在PE路由器R1,R2上查看 Sham-Link
R1#sh ip os sham-links
Sham Link OSPF_SL0 to address 200.1.1.1 is up
Area 1 source address 100.1.1.1
Run as demand circuit
DoNotAge LSA allowed. Cost of using 10 State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40,
Hello due in 00:00:00
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
R2#sh ip os sham-links
Sham Link OSPF_SL0 to address 100.1.1.1 is up
Area 1 source address 200.1.1.1
Run as demand circuit
DoNotAge LSA allowed. Cost of using 10 State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40,
Hello due in 00:00:08
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
说明: Sham-Link建立成功。
(2)在PE路由器R1上查看 MP-BGP 的路由
R1#sh ip bgp vpnv4 all
BGP table version is 14, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale, m multipath, b backup-path, x best-external, f RT-Filter, a additional-path
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1:100 (default for vrf vpn1)
*> 3.3.3.3/32 10.1.13.3 11 32768 ?
r>i4.4.4.4/32 2.2.2.2 11 100 0 ?
*> 10.1.13.0/24 0.0.0.0 0 32768 ?
r>i10.1.24.0/24 2.2.2.2 0 100 0 ?
* i10.1.34.0/24 2.2.2.2 20 100 0 ?
*> 10.1.13.3 20 32768 ?
*> 33.3.3.3/32 10.1.13.3 11 32768 ?
r>i44.4.4.4/32 2.2.2.2 11 100 0 ?
*> 100.1.1.1/32 0.0.0.0 0 32768 i
*>i200.1.1.1/32 2.2.2.2 0 100 0 i
说明: 到达远程场点44.4.4.4 的路径选择从MPLS ××× 骨干网络中走。
(3)在PE路由器R1上查看 VRF 的路由
R1#sh ip route vrf vpn1
Routing Table: vpn1
Codes: L - local, 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, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/11] via 10.1.13.3, 01:15:29, Ethernet1/1
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/21] via 10.1.13.3, 01:07:22, Ethernet1/1
[110/21] via 200.1.1.1, 00:51:32
[110/21] via 2.2.2.2, 00:51:32
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
C 10.1.13.0/24 is directly connected, Ethernet1/1
L 10.1.13.1/32 is directly connected, Ethernet1/1
O 10.1.24.0/24 [110/20] via 2.2.2.2, 00:51:32
O 10.1.34.0/24 [110/20] via 10.1.13.3, 01:07:22, Ethernet1/1
33.0.0.0/32 is subnetted, 1 subnets
O 33.3.3.3 [110/11] via 10.1.13.3, 01:08:09, Ethernet1/1
44.0.0.0/32 is subnetted, 1 subnets
O 44.4.4.4 [110/21] via 2.2.2.2, 00:51:32
100.0.0.0/32 is subnetted, 1 subnets
C 100.1.1.1 is directly connected, Loopback100
200.1.1.0/32 is subnetted, 1 subnets
B 200.1.1.1 [200/0] via 2.2.2.2, 00:54:01
说明: 到达远程场点44.4.4.4 的路径选择从MPLS ××× 骨干网络中走。
注：因为sham-link 是要COST 值的，相当于物理接口，要调整CE 的选路，请调整
sham-link和各接口COST值来完成。
