Configuring an OSPF sham link
Network requirements
As shown in Figure 58:
CE 1 and CE 2 belong to VPN 1 and are connected to PE 1 and PE 2, respectively.
CE 1 and CE 2 are in the same OSPF area.
VPN traffic between CE 1 and CE 2 is required to be forwarded through the MPLS backbone, instead of any route in the OSPF area.
Figure 58: Network diagram
Table 15: Interface and IP address assignment
Device | Interface | IP address | Device | Interface | IP address |
|---|---|---|---|---|---|
CE 1 | Vlan-int11 | 100.1.1.1/24 | CE 2 | Vlan-int11 | 120.1.1.1/24 |
Vlan-int13 | 20.1.1.1/24 | Vlan-int12 | 30.1.1.2/24 | ||
PE 1 | Loop0 | 1.1.1.9/32 | PE 2 | Loop0 | 2.2.2.9/32 |
Loop1 | 3.3.3.3/32 | Loop1 | 5.5.5.5/32 | ||
Vlan-int11 | 100.1.1.2/24 | Vlan-int11 | 120.1.1.2/24 | ||
Vlan-int12 | 10.1.1.1/24 | Vlan-int12 | 10.1.1.2/24 | ||
Switch A | Vlan-int11 | 20.1.1.2/24 | |||
Vlan-int12 | 30.1.1.1/24 |
Configuration procedure
Configure OSPF on the customer networks:
Configure conventional OSPF on CE 1, Switch A, and CE 2 to advertise subnet addresses of the interfaces as shown in Figure 58. Execute the display ip routing-table command to verify that CE 1 and CE 2 have learned the OSPF route to VLAN interface 1 of each other. (Details not shown.)
Configure MPLS L3VPN on the backbone:
# Configure basic MPLS and MPLS LDP on PE 1 to establish LDP LSPs.
<PE1> system-view [PE1] interface loopback 0 [PE1-LoopBack0] ip address 1.1.1.9 32 [PE1-LoopBack0] quit [PE1] mpls lsr-id 1.1.1.9 [PE1] mpls ldp [PE1-ldp] quit [PE1] interface vlan-interface 12 [PE1-Vlan-interface12] ip address 10.1.1.1 24 [PE1-Vlan-interface12] mpls enable [PE1-Vlan-interface12] mpls ldp enable [PE1-Vlan-interface12] quit
# Configure PE 1 to take PE 2 as an MP-IBGP peer.
[PE1] bgp 100 [PE1-bgp] peer 2.2.2.9 as-number 100 [PE1-bgp] peer 2.2.2.9 connect-interface loopback 0 [PE1-bgp] address-family vpnv4 [PE1-bgp-vpnv4] peer 2.2.2.9 enable [PE1-bgp-vpnv4] quit [PE1-bgp] quit
# Configure OSPF on PE 1.
[PE1]ospf 1 [PE1-ospf-1]area 0 [PE1-ospf-1-area-0.0.0.0]network 1.1.1.9 0.0.0.0 [PE1-ospf-1-area-0.0.0.0]network 10.1.1.0 0.0.0.255 [PE1-ospf-1-area-0.0.0.0]quit [PE1-ospf-1]quit
# Configure basic MPLS and MPLS LDP on PE 2 to establish LDP LSPs.
<PE2> system-view [PE2] interface loopback 0 [PE2-LoopBack0] ip address 2.2.2.9 32 [PE2-LoopBack0] quit [PE2] mpls lsr-id 2.2.2.9 [PE2] mpls ldp [PE2-ldp] quit [PE2] interface vlan-interface 12 [PE2-Vlan-interface12] ip address 10.1.1.2 24 [PE2-Vlan-interface12] mpls enable [PE2-Vlan-interface12] mpls ldp enable [PE2-Vlan-interface12] quit
# Configure PE 2 to take PE 1 as an MP-IBGP peer.
[PE2] bgp 100 [PE2-bgp] peer 1.1.1.9 as-number 100 [PE2-bgp] peer 1.1.1.9 connect-interface loopback 0 [PE2-bgp] address-family vpnv4 [PE2-bgp-vpnv4] peer 1.1.1.9 enable [PE2-bgp-vpnv4] quit [PE2-bgp] quit
# Configure OSPF on PE 2.
[PE2]ospf 1 [PE2-ospf-1]area 0 [PE2-ospf-1-area-0.0.0.0]network 2.2.2.9 0.0.0.0 [PE2-ospf-1-area-0.0.0.0]network 10.1.1.0 0.0.0.255 [PE2-ospf-1-area-0.0.0.0]quit [PE2-ospf-1]quit
Configure PEs to allow CE access:
# Configure PE 1.
[PE1] ip vpn-instance vpn1 [PE1-vpn-instance-vpn1] route-distinguisher 100:1 [PE1-vpn-instance-vpn1] vpn-target 1:1 [PE1-vpn-instance-vpn1] quit [PE1] interface vlan-interface 11 [PE1-Vlan-interface11] ip binding vpn-instance vpn1 [PE1-Vlan-interface11] ip address 100.1.1.2 24 [PE1-Vlan-interface11] quit [PE1] ospf 100 vpn-instance vpn1 [PE1-ospf-100] domain-id 10 [PE1-ospf-100] area 1 [PE1-ospf-100-area-0.0.0.1] network 100.1.1.0 0.0.0.255 [PE1-ospf-100-area-0.0.0.1] quit [PE1-ospf-100] quit [PE2] bgp 100 [PE1-bgp] ip vpn-instance vpn1 [PE1-bgp-vpn1] address-family ipv4 unicast [PE1-bgp-ipv4-vpn1] import-route ospf 100 [PE1-bgp-ipv4-vpn1] import-route direct [PE1-bgp-ipv4-vpn1] quit [PE1-bgp-vpn1] quit [PE1-bgp] quit
# Configure PE 2.
[PE2] ip vpn-instance vpn1 [PE2-vpn-instance-vpn1] route-distinguisher 100:2 [PE2-vpn-instance-vpn1] vpn-target 1:1 [PE2-vpn-instance-vpn1] quit [PE2] interface vlan-interface 11 [PE2-Vlan-interface11] ip binding vpn-instance vpn1 [PE2-Vlan-interface11] ip address 120.1.1.2 24 [PE2-Vlan-interface11] quit [PE2] ospf 100 vpn-instance vpn1 [PE2-ospf-100] domain-id 10 [PE2-ospf-100] area 1 [PE2-ospf-100-area-0.0.0.1] network 120.1.1.0 0.0.0.255 [PE2-ospf-100-area-0.0.0.1] quit [PE2-ospf-100] quit [PE2] bgp 100 [PE2-bgp] ip vpn-instance vpn1 [PE2-bgp-vpn1] address-family ipv4 unicast [PE2-bgp-ipv4-vpn1] import-route ospf 100 [PE2-bgp-ipv4-vpn1] import-route direct [PE2-bgp-ipv4-vpn1] quit [PE2-bgp-vpn1] quit [PE2-bgp] quit
# Execute the display ip routing-table vpn-instance command on the PEs to verify that the path to the peer CE is along the OSPF route across the customer networks, instead of the BGP route across the backbone. (Details not shown.)
Configure a sham link:
# Configure PE 1.
[PE1] interface loopback 1 [PE1-LoopBack1] ip binding vpn-instance vpn1 [PE1-LoopBack1] ip address 3.3.3.3 32 [PE1-LoopBack1] quit [PE1] ospf 100 [PE1-ospf-100] area 1 [PE1-ospf-100-area-0.0.0.1] sham-link 3.3.3.3 5.5.5.5 cost 10 [PE1-ospf-100-area-0.0.0.1] quit [PE1-ospf-100] quit
# Configure PE 2.
[PE2] interface loopback 1 [PE2-LoopBack1] ip binding vpn-instance vpn1 [PE2-LoopBack1] ip address 5.5.5.5 32 [PE2-LoopBack1] quit [PE2] ospf 100 [PE2-ospf-100] area 1 [PE2-ospf-100-area-0.0.0.1] sham-link 5.5.5.5 3.3.3.3 cost 10 [PE2-ospf-100-area-0.0.0.1] quit [PE2-ospf-100] quit
Verifying the configuration
# Execute the display ip routing-table vpn-instance command on the PEs to verify the following results: (Details not shown.)
The path to the peer CE is now along the BGP route across the backbone.
A route to the sham link destination address is present.
# Execute the display ip routing-table command on the CEs to verify that the next hop of the OSPF route to the peer CE is the VLAN interface 11 connected to the PE. The VPN traffic to the peer is forwarded over the backbone. (Details not shown.)
# Verify that a sham link has been established on PEs. This example uses PE 1.
[PE1] display ospf sham-link
OSPF Process 100 with Router ID 100.1.1.2
Sham link
Area Neighbor ID Source IP Destination IP State Cost
0.0.0.1 120.1.1.2 3.3.3.3 5.5.5.5 P-2-P 10
# Verify that the peer state is Full on PE 1.
[PE1] display ospf sham-link area 1
OSPF Process 100 with Router ID 100.1.1.2
Sham-Link: 3.3.3.3 --> 5.5.5.5
Neighbor ID: 120.1.1.2 State: Full
Area: 0.0.0.1
Cost: 10 State: P-2-P Type: Sham
Timers: Hello 10s, Dead 40s, Retransmit 5s, Transmit Delay 1s
Request list: 0 Retransmit list: 0