Configuring an OSPF Domain ID for a Layer 3 VPN
This example illustrates how to configure an OSPF domain ID for a VPN by using OSPF as the routing protocol between the PE and CE routers. Routes from an OSPF domain need an OSPF domain ID when they are distributed in BGP as VPN-IPv4 routes in VPNs with multiple OSPF domains. In a VPN connecting multiple OSPF domains, the routes from one domain might overlap with the routes of another.
For more information about OSPF domain IDs and Layer 3 VPNs, see Configuring Routing Between PE and CE Routers in Layer 3 VPNs.
Figure 1 shows this example’s configuration topology. Only the configuration for Router PE1 is provided. The configuration for Router PE2 can be similar to the configuration for Router PE1. There are no special configuration requirements for the CE routers.
Figure 1: Example of a Configuration Using an OSPF Domain ID
For configuration information, see the following sections:
Configuring Interfaces on Router PE1
You need to configure two interfaces for Router PE1—the so-0/0/0 interface for traffic to Router CE1 (San Francisco) and the so-0/0/1 interface for traffic to a P router in the service provider’s network.
Configure the interfaces for Router PE1:
Configuring Routing Options on Router PE1
At the [edit routing-options] hierarchy level, you need to configure the router-id and autonomous-system statements. The router-id statement identifies Router PE1.
Configure the routing options for Router PE1:
Configuring Protocols on Router PE1
On Router PE1, you need to configure MPLS, BGP, OSPF, and LDP
at the
[edit protocols] hierarchy level:
Configuring Policy Options on Router PE1
On Router PE1, you need to configure policies at the [edit policy-options] hierarchy level. These policies ensure that the CE routers in the Layer 3 VPN exchange routing information. In this example, Router CE1 in San Francisco exchanges routing information with Router CE2 in Chicago.
Configure the policy options on the PE1 router:
Configuring the Routing Instance on Router PE1
You need to configure a Layer 3 VPN routing instance on Router PE1. To indicate that the routing instance is for a Layer 3 VPN, add the instance-type vrf statement at the [edit routing-instance routing-instance-name] hierarchy level.
The domain-id statement is configured at the [edit routing-instances routing-options protocols ospf] hierarchy level. As shown in Figure 1, the routing instance on Router PE2 must share the same domain ID as the corresponding routing instance on Router PE1 so that routes from Router CE1 to Router CE2 and vice versa are distributed as Type 3 LSAs. If you configure different OSPF domain IDs in the routing instances for Router PE1 and Router PE2, the routes from each CE router will be distributed as Type 5 LSAs.
Configure the routing instance on Router PE1:
Configuration Summary for Router PE1
Configure Interfaces
Configure Routing Options
Configure Protocols
Configure VPN Policy
Routing Instance for Layer 3 VPN
