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Table Of Contents
Prerequisites for MPLS VPN—L3VPN over GRE
Restrictions for MPLS VPN—L3VPN over GRE
Information About MPLS VPN—L3VPN over GRE
How to Configure MPLS VPN—L3VPN over GRE
Configuring the MPLS VPN—L3VPN over GRE Tunnel Interface
Configuration Examples for MPLS VPN—L3VPN over GRE
MPLS Configuration with MPLS VPN—L3VPN over GRE: Example
Feature Information for MPLS VPN—L3VPN over GRE
MPLS VPN—L3VPN over GRE
First Published: September 29, 2008Last Updated: February 27, 2009The MPLS VPN—L3VPN over GRE feature provides a mechanism for tunneling Multiprotocol Label Switching (MPLS) packets over a non-MPLS network.
The MPLS VPN—L3VPN over GRE feature utilizes MPLS over generic routing encapsulation (MPLSoGRE) to encapsulate MPLS packets inside IP tunnels. This action creates a virtual point-to-point link across non-MPLS networks.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for MPLS VPN—L3VPN over GRE" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS, Catalyst OS, and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for MPLS VPN—L3VPN over GRE
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Prerequisites for MPLS VPN—L3VPN over GRE
Before you configure the MPLS VPN—L3VPN over GRE feature, ensure that your MPLS Virtual Private Network (VPN) is configured and working properly. See the Configuring MPLS Layer 3 VPNs module for information about setting up MPLS VPNs.
Ensure that the following routing protocols are configured and working properly:
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Restrictions for MPLS VPN—L3VPN over GRE
The MPLS VPN—L3VPN over GRE feature does not support the following:
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Information About MPLS VPN—L3VPN over GRE
The MPLS VPN—L3VPN over GRE feature provides a mechanism for tunneling MPLS packets over non-MPLS networks.
MPLS VPN—L3VPN over GRE allows you to create a GRE tunnel across a non-MPLS network. The MPLS packets are encapsulated within the GRE tunnel packets, and the encapsulated packets traverse the non-MPLS network through the GRE tunnel. When GRE tunnel packets are received at the other side of the non-MPLS network, the GRE tunnel packet header is removed and the inner MPLS packet is forwarded to its final destination.
The MPLS VPN—L3VPN over GRE feature supports three GRE tunnel configurations:
PE-to-PE Tunneling
The provider edge-to-provider edge (PE-to-PE) tunneling configuration provides a scalable way to connect multiple customer networks across a non-MPLS network. With this configuration, traffic that is destined to multiple customer networks is multiplexed through a single GRE tunnel.
Note
As shown in Figure 1, the PE routers assign VPN routing and forwarding (VRF) numbers to the customer edge (CE) routers on each side of the non-MPLS network.
The PE routers use routing protocols such as BGP, OSPF, or Routing Information Protocol (RIP) to learn about the IP networks behind the CE routers. The routes to the IP networks behind the CE routers are stored in the associated CE router's VRF routing table.
The PE router on one side of the non-MPLS network uses the routing protocols (that are operating within the non-MPLS network) to learn about the PE router on the other side of the non-MPLS network. The learned routes that are established between the PE routers are then stored in the main or default routing table.
The opposing PE router uses BGP to learn about the routes that are associated with the customer networks behind the PE routers. These learned routes are not known to the non-MPLS network.
For this example, BGP defines a static route to the BGP neighbor (the opposing PE router) through the GRE tunnel that spans the non-MPLS network. Because the routes that are learned by the BGP neighbor include the GRE tunnel next hop, all customer network traffic is sent using the GRE tunnel.
Figure 1 PE-to-PE Tunneling
P-to-PE Tunneling
As shown in Figure 2, the provider-to-provider edge (P-to-PE) tunneling configuration provides a way to connect a PE router (P1) to an MPLS segment (PE-2) across a non-MPLS network. In this configuration, MPLS traffic that is destined to the other side of the non-MPLS network is sent through a single GRE tunnel.
Figure 2 P-to-PE Tunneling
P-to-P Tunneling
As shown in Figure 3, the provider-to-provider (P-to-P) configuration provides a method of connecting two MPLS segments (P1 to P2) across a non-MPLS network. In this configuration, MPLS traffic that is destined to the other side of the non-MPLS network is sent through a single GRE tunnel.
Figure 3 P-to-P Tunneling
How to Configure MPLS VPN—L3VPN over GRE
This section contains the following procedure:
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Configuring the MPLS VPN—L3VPN over GRE Tunnel Interface
To configure the MPLS VPN—L3VPN over GRE feature, you must create a GRE tunnel to span the non-MPLS networks. You must perform this procedure on the devices located at both ends of the GRE tunnel.
Prerequisites
Before configuring the MPLS VPN—L3VPN over GRE feature, ensure that your MPLS VPN and the appropriate routing protocols are configured and working properly. See the "Prerequisites for MPLS VPN—L3VPN over GRE" section.
SUMMARY STEPS
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DETAILED STEPS
Examples
The following example shows a GRE tunnel configuration that spans a non-MPLS network. This example shows the tunnel configuration on the PE devices (PE1 and PE2) located at both ends of the tunnel:
PE1 Configuration
Router# configure terminalRouter(config)# interface Tunnel 1Router(config-if)# ip address 10.1.1.1 255.255.255.0Router(config-if)# tunnel source 10.0.0.1Router(config-if)# tunnel destination 10.0.0.2Router(config-if)# mpls ipPE2 Configuration
Router# configure terminalRouter(config)# interface Tunnel 1Router(config-if)# ip address 10.1.1.2 255.255.255.0Router(config-if)# tunnel source 10.0.0.2Router(config-if)# tunnel destination 10.0.0.1Router(config-if)# mpls ipConfiguration Examples for MPLS VPN—L3VPN over GRE
This section provides the following configuration example for the MPLS VPN—L3VPN over GRE feature:
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MPLS Configuration with MPLS VPN—L3VPN over GRE: Example
The following basic MPLS configuration example uses a GRE tunnel to span a non-MPLS network. This example is similar to the configuration shown in Figure 1.
PE1 Configuration
!mpls ip!ip vrf vpn1rd 100:1route-target import 100:1route-target export 100:1!interface loopback 0ip address 10.2.2.2 255.255.255.255!interface GigabitEthernet 0/1/2ip address 10.1.1.1 255.255.255.0!interface Tunnel 1ip address 10.0.0.1 255.255.255.0tunnel source 10.1.1.1tunnel destination 10.1.1.2mpls ip!interface GigabitEthernet 0/1/3ip vrf forwarding vpn1ip address 10.10.0.1 255.255.255.0!router bgp 100neighbor 10.5.5.5 remote-as 100neighbor 10.5.5.5 update-source loopback0!address-family vpnv4neighbor 10.5.5.5 activateneighbor 10.5.5.5 send community-extended!address-family ipv4 vrf vpn1neighbor 10.10.0.2 remote-as 20neighbor 10.10.0.2 activate!PE2 Configuration
!mpls ip!ip vrf vpn1rd 100:1route-target import 100:1route-target export 100:1!interface loopback 0ip address 10.5.5.5 255.255.255.255!interface GigabitEthernet 0/1/1ip address 10.1.1.2 255.255.255.0!interface Tunnel 1ip address 10.0.0.2 255.255.255.0tunnel source 10.1.1.2tunnel destination 10.1.1.1mpls ip!interface GigabitEthernet 0/0/5ip vrf forwarding vpn1ip address 10.1.2.1 255.255.255.0!router bgp 100neighbor 10.2.2.2 remote-as 100neighbor 10.2.2.2 update-source loopback0!address-family vpnv4neighbor 10.2.2.2 activateneighbor 10.2.2.2 send community-extended!address-family ipv4 vrf vpn1neighbor 10.1.2.2 remote-as 30neighbor 10.1.2.2 activate!Additional References
The following sections provide references related to the MPLS VPN—L3VPN over GRE feature.
Related Documents
Setting up MPLS VPN networks
Interior Gateway Protocols
Cisco IOS XE IP Routing Protocols Configuration Guide, Release 2
Label Distribution Protocol
Multiprotocol Border Gateway Protocol (MP-BGP)
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
RFCs
Technical Assistance
Command Reference
This feature uses no new or modified commands.
Feature Information for MPLS VPN—L3VPN over GRE
Table 1 lists the release history for this feature.
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS, Catalyst OS, and Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
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