MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

The Multiprotocol Label Switching (MPLS) VPN Inter-AS with Autonomous System Boundary Routers (ASBRs) Exchanging VPN-IPv4 Addresses feature allows a MPLS VPN to span service providers and autonomous systems. This module explains how to enable ASBRs to use Exterior Border Gateway Protocol (EBGP) to exchange IPv4 Network Layer Reachability Information (NLRI) in the form of VPN-IPv4 addresses.

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Prerequisites for MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

  • Before you configure Exterior Border Gateway Protocol (EBGP) routing between autonomous systems or subautonomous systems in an Multiprotocol Label Switching (MPLS) VPN, ensure that you have properly configured all MPLS VPN routing instances and sessions. The configuration tasks outlined in this section build from those configuration tasks. Perform the following tasks as described in the Configuring MPLS Layer 3 VPNs module:
    • Define VPN routing instances
    • Configure BGP routing sessions in the MPLS core
    • Configure provider-edge-provider-edge (PE-to-PE) routing sessions in the MPLS core
    • Configure BGP provider-edge-customer-edge (PE-to-CE) routing sessions
    • Configure a VPN-IPv4 EBGP session between directly connected Autonomous System Boundary Routers (ASBRs)

Restrictions for MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Multihop VPN-IPv4 Exterior Border Gateway Protocol (EBGP) is not supported.

Information About MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

MPLS VPN Inter-AS Introduction

An autonomous system is a single network or group of networks that is controlled by a common system administration group and that uses a single, clearly defined routing protocol.

As VPNs grow, their requirements expand. In some cases, VPNs need to reside on different autonomous systems in different geographic areas. Also, some VPNs need to extend across multiple service providers (overlapping VPNs). Regardless of the complexity and location of the VPNs, the connection between autonomous systems must be seamless to the customer.

Benefits of MPLS VPN Inter-AS

An MultiprotocolLabel Switching (MPLS) VPN Inter-AS provides the following benefits:

  • Allows a VPN to cross more than one service provider backbone: Service providers running separate autonomous systems can jointly offer MPLS VPN services to the same customer. A VPN can begin at one customer site and traverse different VPN service provider backbones before arriving at another site of the same customer. Previously, MPLS VPN could traverse only a single Border Gateway Protocol (BGP) autonomous system service provider backbone. This feature allows multiple autonomous systems to form a continuous (and seamless) network between customer sites of a service provider.

  • Allows a VPN to exist in different areas: A service provider can create a VPN in different geographic areas. Having all VPN traffic flow through one point (between the areas) allows for better rate control of network traffic between the areas.

  • Allows confederations to optimize Internal Border Gateway Protocol (IBGP) meshing: IBGP meshing in an autonomous system is more organized and manageable. An autonomous system can be divided into multiple, separate subautonomous systems and then classify them into a single confederation (even though the entire VPN backbone appears as a single autonomous system). This capability allows a service provider to offer MPLS VPNs across the confederation because it supports the exchange of labeled VPN-IPv4 Network Layer Reachability Information (NLRI) between the subautonomous systems that form the confederation.

Use of Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Separate autonomous systems from different service providers can communicate by exchanging IPv4 Network Layer Reachability Information (NLRI) in the form of VPN-IPv4 addresses. The Autonomous System Border Routers (ASBRs) use Exterior Border Gateway Protocol (EBGP) to exchange network reachability information. Then an Interior Gateway Protocol (IGP) distributes the network layer information for VPN-IPv4 prefixes throughout each VPN and each autonomous system. Routing information uses the following protocols:

  • Within an autonomous system, routing information is shared using an IGP.

  • Between autonomous systems, routing information is shared using an EBGP. An EBGP allows a service provider to set up an interdomain routing system that guarantees the loop-free exchange of routing information between separate autonomous systems.

The primary function of an EBGP is to exchange network reachability information between autonomous systems, including information about the list of autonomous system routes. The autonomous systems use EBGP border edge devices to distribute the routes, which include label switching information. Each border edge device rewrites the next hop and labels. See the Information Exchange in an MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses section for more information.

Interautonomous system configurations supported in an MPLS VPN are as follows:

  • Interprovider VPN-- MPLS VPNs that include two or more autonomous systems, connected by separate border edge devices. The autonomous systems exchange routes using EBGP. No IGP or routing information is exchanged between the autonomous systems.

  • BGP confederations-- MPLS VPNs that divide a single autonomous system into multiple subautonomous systems, and classify them as a single, designated confederation. The network recognizes the confederation as a single autonomous system. The peers in the different autonomous systems communicate over EBGP sessions; however, they can exchange route information as if they were IBGP peers.

Information Exchange in an MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

This section contains the following topics:

Transmission of Information in an MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

The figure below illustrates an Multiprotocol Label Switching (MPLS) VPN consisting of two separate autonomous systems. Each autonomous system operates under different administrative control and runs a different Interior Gateway Protocol (IGP). Service providers exchange routing information through Exterior Border Gateway Protocol (EBGP) border edge devices (ASBR1, ASBR2).

Figure 1. EBGP Connection Between Two MPLS VPN Inter-AS Systems with ASBRs Exchanging VPN-IPv4 Addresses

This configuration uses the following process to transmit information:

SUMMARY STEPS

  1. The provider edge device (PE-1) assigns a label for a route before distributing that route. The PE device uses the multiprotocol extensions of Border Gateway Protocol (BGP) to transmit label mapping information. The PE device distributes the route as a VPN-IPv4 address. The address label and the VPN identifier are encoded as part of the IPv4 Network Layer Reachability Information (NLRI).
  2. The two route reflectors (RR-1 and RR-2) reflect VPN-IPv4 internal routes within the autonomous system. The border edge devices (ASBR1 and ASBR2) of the autonomous systems advertise the VPN-IPv4 external routes.
  3. The EBGP border edge device (ASBR1) redistributes the route to the next autonomous system (ASBR2). ASBR1 specifies its own address as the value of the EBGP next-hop attribute and assigns a new label. The address ensures the following:
  4. The EBGP border edge device (ASBR2) redistributes the route in one of the following ways, depending on its configuration:

DETAILED STEPS

Step 1

The provider edge device (PE-1) assigns a label for a route before distributing that route. The PE device uses the multiprotocol extensions of Border Gateway Protocol (BGP) to transmit label mapping information. The PE device distributes the route as a VPN-IPv4 address. The address label and the VPN identifier are encoded as part of the IPv4 Network Layer Reachability Information (NLRI).

Step 2

The two route reflectors (RR-1 and RR-2) reflect VPN-IPv4 internal routes within the autonomous system. The border edge devices (ASBR1 and ASBR2) of the autonomous systems advertise the VPN-IPv4 external routes.

Step 3

The EBGP border edge device (ASBR1) redistributes the route to the next autonomous system (ASBR2). ASBR1 specifies its own address as the value of the EBGP next-hop attribute and assigns a new label. The address ensures the following:

  • The next-hop device is always reachable in the service provider (P) backbone network.

  • Tthe label assigned by the distributing device is properly interpreted. (The label associated with a route must be assigned by the corresponding next-hop device.)

Step 4

The EBGP border edge device (ASBR2) redistributes the route in one of the following ways, depending on its configuration:

  • If the IBGP neighbors are configured with the neighbor next-hop-self command, ASBR2 changes the next-hop address of updates received from the EBGP peer, then forwards it.

  • If the IBGP neighbors are not configured with the neighbor next-hop-self command, the next-hop address does not change. ASBR2 must propagate a host route for the EBGP peer through the IGP. To propagate the EBGP VPN-IPv4 neighbor host route, use the redistribute connected subnets command. The EBGP VPN-IPv4 neighbor host route is automatically installed in the routing table when the neighbor comes up. This is essential to establish the label switched path between PE devices in different autonomous systems.

Exchange of VPN Routing Information in an MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Autonomous systems exchange VPN routing information (routes and labels) to establish connections. To control connections between autonomous systems, the provider edge (PE) devices and Exterior Border Gateway Protocol (EBGP) border edge devices maintain a Label Forwarding Information Base (LFIB). The LFIB manages the labels and routes that the PE devices and EBGP border edge devices receive during the exchange of VPN information.

The figure below illustrates the exchange of VPN route and label information between autonomous systems. The autonomous systems use the following conditions to exchange VPN routing information:

  • Routing information includes:

    • The destination network (N)

    • The next-hop field associated with the distributing device

    • A local MPLS label (L)

  • An RD1: route distinguisher is part of a destination network address. It makes the VPN-IPv4 route globally unique in the VPN service provider environment.

  • The Autonomous System Border Routers (ASBRs) are configured to change the next-hop (next hop-self) when sending VPN-IPv4 Network Layer Reachability Information (NLRI) to the Internal Border Gateway Protocol (IBGP) neighbors. Therefore, the ASBRs must allocate a new label when they forward the NLRI to the IBGP neighbors.

Figure 2. Exchanging Routes and Labels Between MPLS VPN Inter-AS Systems with ASBRs Exchanging VPN-IPv4 Addresses

The figure below illustrates the exchange of VPN route and label information between autonomous systems. The only difference is that ASBR2 is configured with the redistribute connected command, which propagates the host routes to all PEs. The redistribute connected command is necessary because ASBR2 is not configured to change the next-hop address.

Figure 3. Exchanging Routes and Labels with the redistribute connected Command in an MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Packet Forwarding Between MPLS VPN Inter-AS Systems with ASBRs Exchanging VPN-IPv4 Addresses

The figure below illustrates how packets are forwarded between autonomous systems in an interprovider network using the following packet forwarding method.

Packets are forwarded to their destination by means of Multiprotocol Label Switching (MPLS). Packets use the routing information stored in the Label Forwarding Information Base (LFIB) of each provider edge (PE) device and Exterior Border Gateway Protocol (EBGP) border edge device.

The service provider VPN backbone uses dynamic label switching to forward labels.

Each autonomous system uses standard multilevel labeling to forward packets between the edges of the autonomous system devices (for example, from CE-5 to PE-3). Between autonomous systems, only a single level of labeling is used, corresponding to the advertised route.

A data packet carries two levels of labels when traversing the VPN backbone:

  • The first label (IGP route label) directs the packet to the correct PE device or EBGP border edge device. (For example, the Interior Gateway Protocol (IGP) label of ASBR2 points to the ASBR2 border edge device.)

  • The second label (VPN route label) directs the packet to the appropriate PE device or EBGP border edge device.

Figure 4. Forwarding Packets Between MPLS VPN Inter-AS Systems with ASBRs Exchanging VPN-IPv4 Addresses

The figure below shows the same packet forwarding method as described in the figure above, except the EBGP device (ASBR1) forwards the packet without reassigning it a new label.

Figure 5. Forwarding Packets Without a New Label Assignment Between MPLS VPN Inter-AS Systems with ASBRs Exchanging VPN-IPv4 Addresses

Use of a Confederation for MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

A confederation is a collection of multiple subautonomous systems that are grouped together. A confederation reduces the total number of peer devices in an autonomous system. A confederation divides an autonomous system into subautonomous systems and assigns a confederation identifier to the autonomous systems. A VPN can span service providers running in separate autonomous systems or in multiple subautonomous systems that form a confederation.

In a confederation, each subautonomous system is fully meshed with other subautonomous systems. The subautonomous systems communicate using an Interior Gateway Protocol (IGP), such as Open Shortest Path First (OSPF) or Intermediate System-to-Intermediate System (IS-IS). Each subautonomous system also has an Exterior Border Gateway Protocol (EBGP) connection to the other subautonomous systems. The confederation EBGP (CEBGP) border edge devices forward next-hop-self addresses between the specified subautonomous systems. The next-hop-self address forces the Border Gateway Protocol (BGP) to use a specified address as the next hop rather than letting the protocol choose the next hop.

You can configure a confederation with separate subautonomous systems in either of two ways:

  • You can configure a device to forward next-hop-self addresses between only the CEBGP border edge devices (both directions). The subautonomous systems (IBGP peers) at the subautonomous system border do not forward the next-hop-self address. Each subautonomous system runs as a single IGP domain. However, the CEBGP border edge device addresses are known in the IGP domains.

  • You can configure a device to forward next-hop-self addresses between the CEBGP border edge devices (both directions) and within the IBGP peers at the subautonomous system border. Each subautonomous system runs as a single IGP domain but also forwards next-hop-self addresses between the PE devices in the domain. The CEBGP border edge device addresses are known in the IGP domains.

The figure below illustrates a typical MPLS VPN confederation configuration. In this confederation configuration:

  • The two CEBGP border edge devices exchange VPN-IPv4 addresses with labels between the two subautonomous systems.

  • The distributing device changes the next-hop addresses and labels and uses a next-hop-self address.

  • IGP-1 and IGP-2 know the addresses of CEBGP-1 and CEBGP-2.

Figure 6. EBGP Connection Between Two Subautonomous Systems in a Confederation

In this confederation configuration:

  • CEBGP border edge devices function as neighboring peers between the subautonomous systems. The subautonomous systems use EBGP to exchange route information.

  • Each CEBGP border edge device (CEBGP-1, CEBGP-2) assigns a label for the route before distributing the route to the next subautonomous system. The CEBGP border edge device distributes the route as a VPN-IPv4 address by using the multiprotocol extensions of BGP. The label and the VPN identifier are encoded as part of the IPv4 Network Layer Reachability Information (NLRI).

  • Each provider edge (PE) and CEBGP border edge device assigns its own label to each VPN-IPv4 address prefix before redistributing the routes. The CEBGP border edge devices exchange VPN-IPv4 addresses with the labels. The next-hop-self address is included in the label (as the value of the EBGP next-hop attribute). Within the subautonomous systems, the CEBGP border edge device address is distributed throughout the IBGP neighbors, and the two CEBGP border edge devices are known to both confederations.

How to Configure MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Configuring the ASBRs to Exchange VPN-IPv4 Addresses

To configure an Exterior Border Gateway Protocol (EBGP) Autonomous System Border Router (ASBR) to exchange VPN-IPv4 routes with another autonomous system, perform this task.


Note

Issue the redistribute connected subnets command in the Interior Gateway Protocol (IGP) configuration portion of the device to propagate host routes for VPN-IPv4 EBGP neighbors to other devices and provider edge devices. Alternatively, you can specify the next-hop-self address when you configure Internal Border Gateway Protocol (IBGP) neighbors.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. router bgp as-number
  4. no bgp default route-target filter
  5. address-family vpnv4 [unicast]
  6. neighbor peer-group-name remote-as as-number
  7. neighbor peer-group-name activate
  8. exit-address-family
  9. end

DETAILED STEPS

  Command or Action Purpose

Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

router bgp as-number

Example:


Device(config)# router bgp 1

Creates an EBGP routing process and assigns it an autonomous system number.

  • The autonomous system number is passed along and identifies the device to EBGP devices in another autonomous system.

Step 4

no bgp default route-target filter

Example:


Device(config)# no bgp default route-target filter

Disables BGP route-target filtering and places the device in configuration mode.

  • All received BGP VPN-IPv4 routes are accepted by the device.

Step 5

address-family vpnv4 [unicast]

Example:


Device(config-router)# address-family vpnv4

Configures a routing session to carry VPNv4 addresses across the VPN backbone and places the device in address family configuration mode.

  • Each address has been made globally unique by the addition of an 8-byte route distinguisher (RD).

  • The unicast keyword specifies a unicast prefix.

Step 6

neighbor peer-group-name remote-as as-number

Example:


Device(config-router-af)# neighbor 1 remote-as 2

Enters the address family configuration mode and specifies a neighboring EBGP peer group.

  • This EBGP peer group is identified to the specified autonomous system.

Step 7

neighbor peer-group-name activate

Example:


Device(config-router-af)# neighbor 1 activate

Activates the advertisement of the VPNv4 address family to a neighboring EBGP device.

Step 8

exit-address-family

Example:


Device(config-router-af)# exit-address-family

Exits from the address family submode of the router configuration mode.

Step 9

end

Example:


Device(config)# end

Exits to privileged EXEC mode.

Configuring EBGP Routing to Exchange VPN Routes Between Subautonomous Systems in a Confederation

Perform this task to configure EBGP routing to exchange VPN routes between subautonomous systems in a confederation.


Note

To ensure that the host routes for VPN-IPv4 EBGP neighbors are propagated (by means of the IGP) to the other devices and provider edge devices, specify the redistribute connected command in the IGP configuration portion of the CEBGP device. If you are using OSPF, make sure that the OSPF process is not enabled on the CEBGP interface where the “redistribute connected” subnet exists.


Note

In this confederation, subautonomous system IGP domains must know the addresses of CEBGP-1 and CEBGP-2. If you do not specify a next-hop-self address as part of the router configuration, ensure that the addresses of all PE devices in the subautonomous system are distributed throughout the network, not just the addresses of CEBGP-1 and CEBGP-2.

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. router bgp sub-autonomous-system
  4. bgp confederation identifier as-number
  5. bgp conferderation peers sub-autonomous-system
  6. no bgp default route-target filter
  7. address-family vpnv4 [unicast]
  8. neighbor peer-group-name remote-as as-number
  9. neighbor peer-group-name next-hop-self
  10. neighbor peer-group-name activate
  11. exit-address-family
  12. end

DETAILED STEPS

  Command or Action Purpose

Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Device# configure terminal

Enters global configuration mode.

Step 3

router bgp sub-autonomous-system

Example:


Device(config)# router bgp 2

Creates an EBGP routing process and assigns it an autonomous system number and enters the device in configuration mode.

  • The subautonomous system number is passed along to identify the device to EBGP devices in other subautonomous systems.

Step 4

bgp confederation identifier as-number

Example:


Device(config-router)# bgp confederation identifier 100

Defines an EBGP confederation by specifying a confederation identifier associated with each subautonomous system.

  • The subautonomous systems appear as a single autonomous system.

Step 5

bgp conferderation peers sub-autonomous-system

Example:


Device(config-router)# bgp confederation peers 1

Specifies the subautonomous systems that belong to the confederation (identifies neighbors of other subautonomous systems within the confederation as special EBGP peers).

Step 6

no bgp default route-target filter

Example:


Device(config-router)# no bgp default route-target filter

Disables BGP route-target community filtering. All received BGP VPN-IPv4 routes are accepted by the device.

Step 7

address-family vpnv4 [unicast]

Example:


Device(config-router)# address-family vpnv4

Configures a routing session to carry VPNv4 addresses across the VPN backbone. Each address is made globally unique by the addition of an 8-byte RD. Enters address family configuration mode.

  • The unicast keyword specifies a unicast prefix.

Step 8

neighbor peer-group-name remote-as as-number

Example:


Device(config-router-af)# neighbor 1 remote-as 1

Enters the address family configuration mode and specifies a neighboring EBGP peer group.

  • This EBGP peer group is identified to the specified subautonomous system.

Step 9

neighbor peer-group-name next-hop-self

Example:


Device(config-router-af)# neighbor 1 next-hop-self

Advertises the device as the next hop for the specified neighbor.

  • If a next-hop-self address is specified as part of the router configuration, the redistribute connected command need not be used.

Step 10

neighbor peer-group-name activate

Example:


Device(config-router-af)# neighbor R activate

Activates the advertisement of the VPNv4 address family to a neighboring PE device in the specified subautonomous system.

Step 11

exit-address-family

Example:


Device(config-router-af)# exit-address-family

Exits from the address family submode of the router configuration mode.

Step 12

end

Example:


Device(config)# end

Exits to privileged EXEC mode.

Verifying Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Perform this task to display the VPN-IPv4 Label Forwarding Information Base (LFIB) entries.

SUMMARY STEPS

  1. enable
  2. show ip bgp vpnv4 {all | rd route-distinguisher | vrf vrf-name} [summary] [labels]
  3. show mpls forwarding-table [network {mask | length} | labels label [-label] | interface interface | next-hop address | lsp-tunnel [tunnel-id]] [vrf vrf-name] [detail]
  4. disable

DETAILED STEPS

  Command or Action Purpose

Step 1

enable

Example:


Device> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

show ip bgp vpnv4 {all | rd route-distinguisher | vrf vrf-name} [summary] [labels]

Example:


Device# show ip bgp vpnv4 all labels

Displays VPN address information from the BGP table.

  • Use the all and labels keywords to display information about all VPNv4 labels.

Step 3

show mpls forwarding-table [network {mask | length} | labels label [-label] | interface interface | next-hop address | lsp-tunnel [tunnel-id]] [vrf vrf-name] [detail]

Example:


Device# show mpls forwarding-table

Displays the contents of the MPLS LFIB (such as VPNv4 prefix/length and BGP next-hop destination for the route).

Step 4

disable

Example:


Device# disable

Returns to user EXEC mode.

Configuration Examples for MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Example: Configuring MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

The network topology in the figure below shows two autonomous systems, which are configured as follows:

  • Autonomous system 1 (AS1) includes provider edge 1 (PE1), P1, and Exterior Border Gateway Protocol 1(EBGP1). The Interior Gateway Protocol (IGP) is Open Shortest Path First(OSPF).

  • Autonomous system 2 (AS2) includes PE2, P2, and EBGP2. The IGP is Intermediate System to Intermediate System (IS-IS).

  • Customer edge 1 (CE1) and CE2 belong to the same VPN, which is called VPN1.

  • The P devices are route reflectors.

  • EBGP1 is configured with the redistribute connected subnets command.

  • EBGP2 is configured with the neighbor next-hop-self command.

Figure 7. Configuring Two Autonomous Systems

Example: Configuration for Autonomous System 1 CE1

The following example shows how to configure CE1 in VPN1 in a topology with two autonomous systems: 


interface Loopback1 
 ip address 10.1.0.4 255.0.0.0 
! 
interface GigabitEthernet0/0/0 
 		no ip address 
 encapsulation frame-relay 
 frame-relay intf-type dce 
! 
interface GigabitEthernet0/5/3 point-to-point 
  ip address 10.1.0.2 255.0.0.0 
 frame-relay interface-dlci 22 
! 
router ospf 1 
 network 192.168.3.0 255.255.0.0 area 0

Example: Configuration for Autonomous System 1 PE1

The following example shows how to configure PE1 in AS1 in a topology with two autonomous systems: 


ip cef 
! 
ip vrf V1 
 rd 1:105 
 route-target export 1:100 
 route-target import 1:100 
! 
interface GigabitEthernet0/0/0
 no ip address 
 encapsulation frame-relay 
 no fair-queue 
 clockrate 2000000 
! 
interface GigabitEthernet0/0/0.3 point-to-point 
 ip vrf forwarding V1 
 ip address 192.168.2.4 255.255.0.0 
 frame-relay interface-dlci 22 
! 
interface GigabitEthernet0/5/3 
 ip address 192.168.3.5 255.255.0.0 
 tag-switching ip 
! 
router ospf 1 
 log-adjacency-changes 
 network 192.168.41.0 255.255.0.0 area 0 
! 
router ospf 10 vrf V1 
 log-adjacency-changes 
 redistribute bgp 1 metric 100 subnets 
 network 192.168.41.0 255.255.0.0 area 0 
! 
router bgp 1 
 no synchronization 
 neighbor 1 peer-group 
 neighbor 1 remote-as 1 
 neighbor 1 update-source Loopback0 
 neighbor 192.168.11.10 peer-group R 
 no auto-summary 
 ! 
 address-family ipv4 vrf V1 
  redistribute ospf 10 
  no auto-summary 
  no synchronization 
  exit-address-family 
 ! 
 address-family vpnv4 
  neighbor R activate 
  neighbor R send-community extended 
  neighbor 192.168.11.10 peer-group R 
  no auto-summary 
  exit-address-family

Example: Configuration for Autonomous System 1 P1

The following example shows how to configure P1 in AS1 in a topology with two autonomous systems: 


ip cef 
! 
interface Loopback0 
 ip address 10.1.2.1 255.0.0.0 
! 
interface GigabitEthernet0/4/7 
 ip address 10.1.0.4 255.0.0.0 
 tag-switching ip 
! 
interface GigabitEthernet0/5/3 
 ip address 10.2.0.3 255.0.0.0 
 duplex auto 
 speed auto 
 tag-switching ip 
! 
router ospf 1 
 log-adjacency-changes 
 network 10.1.0.2 255.0.0.0 area 0 
! 
router bgp 1 
 no synchronization 
 bgp log-neighbor-changes 
 neighbor R peer-group 
 neighbor R remote-as 1 
 neighbor R update-source Loopback0 
 neighbor R route-reflector-client 
 neighbor 192.168.3.4 peer-group R 
 neighbor 192.168.3.5 peer-group R 
 ! 
 address-family vpnv4 
  neighbor R activate 
  neighbor R route-reflector-client 
  neighbor R send-community extended 
  neighbor 192.168.3.4 peer-group R 
  neighbor 192.168.3.5 peer-group R 
  exit-address-family

Example: Configuration for Autonomous System 1 EBGP1

The following example shows how to configure EBGP1 in AS1 in a topology with two autonomous systems: 

ip cef 
! 
interface Loopback0 
 ip address 10.2.2.1 255.0.0.0 
! 
! 
ip cef 
! 
interface Loopback0 
 ip address 10.2.2.1 255.0.0.0 
! 
interface GigabitEthernetEthernet0/5/3 
 ip address 10.1.0.5 255.0.0.0 
 tag-switching ip 
! 
interface GigabitEthernet0/0/0 
! 
interface GigabitEthernet0/0/0.1 point-to-point 
! 
router ospf 1 
 log-adjacency-changes 
 redistribute connected subnets 
 network 10.1.0.5 255.0.0.0 area 0 
! 
router bgp 1 
 no synchronization 
 no bgp default route-target filter 
 bgp log-neighbor-changes 
 neighbor R peer-group 
 neighbor R remote-as 1 
 neighbor R update-source Loopback0 
 neighbor 10.1.0.2 remote-as 2 
 neighbor 10.1.0.2 peer-group R 
 no auto-summary 
 ! 
 address-family vpnv4 
  neighbor R activate 
  neighbor R send-community extended 
  neighbor 10.1.0.2 activate 
  neighbor 10.1.0.2 send-community extended 
  neighbor 10.1.0.2 peer-group R 
  no auto-summary 
  exit-address-family

Example: Configuration for Autonomous System 2 EBGP2

The following example shows how to configure EBGP2 in AS2 in a topology with two autonomous systems: 

ip cef 
! 
ip vrf V1 
 rd 2:103 
 route-target export 1:100 
 route-target import 1:100 
! 
interface Loopback0 
 ip address 10.1.1.2 255.0.0.0 
 ip router isis 
! 
interface Loopback1 
 ip vrf forwarding V1 
 ip address 10.1.1.2 255.0.0.0 
! 
interface GigabitEthernet0/4/7
 no ip address 
 encapsulation frame-relay 
 load-interval 30 
 no fair-queue 
 clockrate 2000000 
! 
interface GigabitEthernet0/0/3 point-to-point 
 ip unnumbered Loopback0 
 ip router isis 
 tag-switching ip 
 frame-relay interface-dlci 23 
! 
interface GigabitEthernet0/0/4 
 no ip address 
 atm clock INTERNAL 
 no atm scrambling cell-payload 
 no atm ilmi-keepalive 
! 
interface GigabitEthernet0/0/4.1 point-to-point 
 ip address 10.1.0.5 255.0.0.0 
 pvc 1/100 
! 
router isis 
 net 49.0002.0000.0000.0003.00 
! 
router bgp 2 
 no synchronization 
 no bgp default route-target filter 
 bgp log-neighbor-changes 
 neighbor 10.1.0.1 remote-as 1 
 neighbor 10.1.1.2 remote-as 2 
 neighbor 10.1.1.2 update-source Loopback0 
 neighbor 10.1.1.2 next-hop-self 
! 
 address-family ipv4 vrf V1 
  redistribute connected 
  no auto-summary 
  no synchronization 
  exit-address-family 
 ! 
 address-family vpnv4 
  neighbor 10.1.0.1 activate 
  neighbor 10.1.0.1 send-community extended 
  neighbor 10.1.1.2 activate 
  neighbor 10.1.1.2 next-hop-self 
  neighbor 10.1.1.2 send-community extended 
  exit-address-family

Example: Configuration for Autonomous System 2 P2

The following example shows how to configure P2 in AS2 in a topology with two autonomous systems: 


ip cef 
! 
ip vrf V1 
 rd 2:108 
 route-target export 1:100 
 route-target import 1:100 
! 
interface Loopback0 
 ip address 10.1.0.2 255.0.0.0 
 ip router isis 
! 
interface Loopback1 
 ip vrf forwarding V1 
 ip address 10.1.0.2 255.0.0.0 
! 
interface GigabitEthernet0/0/0 
 ip address 10.2.1.4 255.0.0.0 
 ip router isis 
 tag-switching ip 
! 
interface GigabitEthernet0/0/3 
 no ip address 
 encapsulation frame-relay 
 frame-relay intf-type dce 
! 
interface GigabitEthernet0/0/3.1 point-to-point 
 ip unnumbered Loopback0 
 ip router isis 
 tag-switching ip 
 frame-relay interface-dlci 23 
! 
router isis 
 net aa.0002.0000.0000.0008.00 
! 
router bgp 2 
 no synchronization 
 bgp log-neighbor-changes 
 neighbor R peer-group 
 neighbor R remote-as 2 
 neighbor R update-source Loopback0 
 neighbor R route-reflector-client 
 neighbor 10.1.2.1 peer-group R 
 neighbor 10.0.1.2 peer-group R 
 ! 
 address-family ipv4 vrf V1 
  redistribute connected 
  no auto-summary 
  no synchronization 
  exit-address-family 
 ! 
 address-family vpnv4 
  neighbor R activate 
  neighbor R route-reflector-client 
  neighbor R send-community extended 
  neighbor 10.1.2.1 peer-group R 
  neighbor 10.0.1.2 peer-group R 
  exit-address-family

Example: Configuration for Autonomous System 2 PE2

The following example shows how to configure PE2 in AS2 in a topology with two autonomous systems: 


ip cef 
! 
ip vrf V1 
 rd 2:109 
 route-target export 1:100 
 route-target import 1:100 
! 
interface Loopback0 
 ip address 192.168.11.10 255.255.0.0 
 ip router isis 
! 
interface Loopback1 
 ip vrf forwarding V1 
 ip address 192.168.11.10 255.255.0.0 
! 
interface GigabitEthernet0/5/3
 no ip address 
 encapsulation frame-relay 
 frame-relay intf-type dce 
 no fair-queue 
 clockrate 2000000 
! 
interface GigabitEthernet0/5/3.1 point-to-point 
 ip vrf forwarding V1 
 ip unnumbered Loopback1 
 frame-relay interface-dlci 24 
! 
interface GigabitEthernet0/0/0 
 ip address 192.168.2.10 255.255.0.0 
 ip router isis 
 tag-switching ip 
! 
router ospf 10 vrf V1 
 log-adjacency-changes 
 redistribute bgp 2 subnets 
 network 192.168.2.2 255.255.0.0 area 0 
! 
router isis 
 net 49.0002.0000.0000.0009.00 
! 
router bgp 2 
 no synchronization 
 bgp log-neighbor-changes 
 neighbor 192.168.3.2 remote-as 2 
 neighbor 192.168.3.2 update-source Loopback0 
 ! 
 address-family ipv4 vrf V1 
  redistribute connected 
  redistribute ospf 10 
  no auto-summary 
  no synchronization 
  exit-address-family
 ! 
 address-family vpnv4 
  neighbor 192.168.3.2 activate 
  neighbor 192.168.3.2 send-community extended 
  exit-address-family v

Example: Configuration for Autonomous System 2 CE2

The following example shows how to configure CE2 in VPN1 in a topology with two autonomous systems: 


interface Loopback0 
 ip address 192.168.2.2 255.255.0.0 
! 
interface GigabitEthernet0/0/0 
 no ip address 
 encapsulation frame-relay 
 no fair-queue 
 clockrate 2000000 
! 
interface GigabitEthernet0/0/0.1 point-to-point 
 ip unnumbered Loopback0 
 frame-relay interface-dlci 24 
! 
router ospf 1 
 network 192.168.4.6 255.255.0.0 area 0

Example: Configuring MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses in a Confederation

The network topology in the figure below shows a single internet service provider, which is partitioning the backbone with confederations. The autonomous system number of the provider is 100. The two autonomous systems run their own IGPs and are configured as follows:

  • Autonomous system 1 (AS1) includes provider edge 1 (PE1), P1, Autonomous System Border Router 1 (ASBR1). The Interior Gateway Protocol (IGP) is Open Shortest Path First (OSPF).

  • Autonomous system 2 (AS2) includes PE2, P2, ASBR2. The IGP is Intermediate System to Intermediate System (IS-IS).

  • Customer edge 1 (CE1) and CE2 belong to the same VPN, which is called VPN1.

  • The P devices are route reflectors.

  • ASBR1 is configured with the redistribute connected subnets command.

  • ASBR2 is configured with the neighbor next-hop-self command.

Figure 8. Configuring Two Autonomous Systems in a Confederation

Example: Configuration for Autonomous System 1 CE1

The following example shows how to configure CE1 in VPN1 in a confederation topology: 


interface Loopback1 
 ip address 192.168.3.4 255.255.255.255 
! 
interface GigabitEthernet0/4/7 
 no ip address 
 encapsulation frame-relay 
 frame-relay intf-type dce 
! 
interface GigabitEthernet0/4/7.1 point-to-point 
 ip address 192.168.1.3 255.255.0.0 
 frame-relay interface-dlci 22 
! 
router ospf 1 
 network 192.168.0.1 255.255.0.0 area 0

Example: Configuration for Autonomous System 1 PE1

The following example shows how to configure PE1 in AS1 in a confederation topology: 


ip cef 
! 
ip vrf V1 
 rd 1:105 
 route-target export 1:100 
 route-target import 1:100 
! 
interface GigabitEthernet0/0/0
 no ip address 
 encapsulation frame-relay 
 no fair-queue 
 clockrate 2000000 
! 
interface GigabitEthernet0/0/0.3 point-to-point 
 ip vrf forwarding V1 
 ip address 10.0.2.4 255.0.0.0 
 frame-relay interface-dlci 22 
! 
interface GigabitEthernet0/4/7
 ip address 10.1.2.6 255.0.0.0 
 tag-switching ip 
! 
router ospf 1 
 log-adjacency-changes 
 network 10.1.8.4 255.0.0.0 area 0 
! 
router ospf 10 vrf V1 
 log-adjacency-changes 
 redistribute bgp 1 metric 100 subnets 
 network 10.1.8.4 255.0.0.0 area 0 
! 
router bgp 1 
 no synchronization 
 bgp confederation identifier 100 
 bgp confederation identifier 100 
 neighbor 1 peer-group 
 neighbor 1 remote-as 1 
 neighbor 1 update-source Loopback0 
 neighbor 10.2.1.2 peer-group R 
 no auto-summary 
 ! 
 address-family ipv4 vrf V1 
  redistribute ospf 10 
  no auto-summary 
  no synchronization 
  exit-address-family 
 ! 
 address-family vpnv4 
  neighbor R activate 
  neighbor R send-community extended 
  neighbor 10.2.1.2 peer-group R 
  no auto-summary 
  exit-address-family

Example: Configuration for Autonomous System 1 P1

The following example shows how to configure P1 in AS1 in a confederation topology: 


ip cef 
! 
interface Loopback0 
 ip address 10.0.0.2 255.0.0.0 
! 
interface GigabitEthernet0/0/0 
 ip address 10.2.1.1 255.0.0.0 
 tag-switching ip 
! 
interface GigabitEthernet0/4/7 
 ip address 10.2.2.1 255.0.0.0 
 duplex auto 
 speed auto 
 tag-switching ip 
! 
router ospf 1 
 log-adjacency-changes 
 network 10.1.2.2 255.0.0.0 area 0 
! 
router bgp 1 
 no synchronization 
 bgp log-neighbor-changes 
 bgp confederation identifier 100 
 neighbor R peer-group 
 neighbor R remote-as 1 
 neighbor R update-source Loopback0 
 neighbor R route-reflector-client 
 neighbor 10.0.0.4 peer-group R 
 neighbor 10.0.0.5 peer-group R 
 ! 
 address-family vpnv4 
  neighbor R activate 
  neighbor R route-reflector-client 
  neighbor R send-community extended 
  neighbor 10.1.0.4 peer-group R 
  neighbor 10.1.0.5 peer-group R 
  exit-address-family

Example: Configuration for Autonomous System 1 ASBR1

The following example shows how to configure ASBR1 in AS1 in a confederation topology: 


ip cef 
! 
interface Loopback0 
 ip address 10.0.0.4 255.0.0.0 
! 
interface GigabitEthernet0/0/0 
 ip address 10.2.1.40 255.255.255.0 
 tag-switching ip 
! 
interface GigabitEthernet0/5/3 
 no ip address 
 no atm scrambling cell-payload 
 no atm ilmi-keepalive 
! 
interface GigabitEthernet0/5/3.1 point-to-point 
 ip address 10.0.0.1 255.0.0.0 
 pvc 1/100 
! 
router ospf 1 
 log-adjacency-changes 
 redistribute connected subnets 
 network 10.0.0.3 255.0.0.0 area 0 
! 
router bgp 1 
 no synchronization 
 no bgp default route-target filter 
 bgp log-neighbor-changes 
 bgp confederation identifier 100 
 bgp confederation peers 1 
 neighbor R peer-group 
 neighbor R remote-as 1 
 neighbor R update-source Loopback0 
 neighbor 10.0.0.2 remote-as 2 
 neighbor 10.0.0.2 next-hop-self 
 neighbor 10.0.0.2 peer-group R 
 no auto-summary 
 ! 
 address-family vpnv4 
  neighbor R activate 
  neighbor R send-community extended 
  neighbor 10.0.0.2 activate 
  neighbor 10.0.0.2 next-hop-self 
  neighbor 10.0.0.2 send-community extended 
  neighbor 10.0.0.2 peer-group R 
  no auto-summary 
  exit-address-family

Example: Configuration for Autonomous System 2 ASBR2

The following example shows how to configure ASBR2 in AS2 in a confederation topology: 


ip cef 
! 
ip vrf V1 
 rd 2:103 
 route-target export 1:100 
 route-target import 1:100 
! 
interface Loopback0 
 ip address 10.0.0.3 255.0.0.0 
 ip router isis 
! 
interface Loopback1 
 ip vrf forwarding V1 
 ip address 10.0.0.3 255.0.0.0 
! 
interface GigabitEthernet0/4/7
 no ip address 
 encapsulation frame-relay 
 load-interval 30 
 no fair-queue 
 clockrate 2000000 
! 
interface GigabitEthernet0/4/7.2 point-to-point 
 ip unnumbered Loopback0 
 ip router isis 
 tag-switching ip 
 frame-relay interface-dlci 23 
! 
interface GigabitEthernet0/5/3 
 no ip address 
 atm clock INTERNAL 
 no atm scrambling cell-payload 
 no atm ilmi-keepalive 
! 
interface GigabitEthernet0/5/3.1 point-to-point 
 ip address 10.0.0.2 255.0.0.0 
 pvc 1/100 
! 
router isis 
 net aa.0002.0000.0000.0003.00 
! 
router bgp 2 
 no synchronization 
 no bgp default route-target filter 
 bgp log-neighbor-changes 
 bgp confederation identifier 100 
 bgp confederation peers 1 
 neighbor 10.0.0.1 remote-as 1 
 neighbor 10.0.0.1 next-hop-self 
 neighbor 10.0.0.8 remote-as 2 
 neighbor 10.0.0.8 update-source Loopback0 
 neighbor 10.0.0.8 next-hop-self 
 ! 
 address-family ipv4 vrf V1 
  redistribute connected 
  no auto-summary 
  no synchronization 
  exit-address-family 
 ! 
 address-family vpnv4 
  neighbor 10.0.0.1 activate 
  neighbor 10.0.0.1 next-hop-self 
  neighbor 10.0.0.1 send-community extended 
  neighbor 10.0.0.8 activate 
  neighbor 10.0.0.8 next-hop-self 
  neighbor 10.0.0.8 send-community extended 
  exit-address-family

Example: Configuration for Autonomous System 2 P2

The following example shows how to configure P2 in AS2 in a confederation topology: 


ip cef 
! 
ip vrf V1 
 rd 2:108 
 route-target export 1:100 
 route-target import 1:100 
! 
interface Loopback0 
 ip address 10.0.0.8 255.0.0.0 
 ip router isis 
! 
interface Loopback1 
 ip vrf forwarding V1 
 ip address 10.0.0.8 255.0.0.0 
! 
interface GigabitEthernet0/0/0 
 ip address 10.9.1.2 255.0.0.0 
 ip router isis 
 tag-switching ip 
! 
interface GigabitEthernet0/5/3 
 no ip address 
 encapsulation frame-relay 
 frame-relay intf-type dce 
! 
interface GigabitEthernet0/5/3.1 point-to-point 
 ip unnumbered Loopback0 
 ip router isis 
 tag-switching ip 
 frame-relay interface-dlci 23 
! 
router isis 
 net aa.0002.0000.0000.0008.00 
! 
router bgp 2 
 no synchronization 
 bgp log-neighbor-changes 
 bgp confederation identifier 100 
 neighbor R peer-group 
 neighbor R remote-as 2 
 neighbor R update-source Loopback0 
 neighbor R route-reflector-client 
 neighbor 10.0.0.3 peer-group R 
 neighbor 10.0.0.9 peer-group R 
 ! 
 address-family ipv4 vrf V1 
  redistribute connected 
  no auto-summary 
  no synchronization 
  exit-address-family 
 ! 
 address-family vpnv4 
  neighbor R activate 
  neighbor R route-reflector-client 
  neighbor R send-community extended 
  neighbor 10.0.0.3 peer-group R 
  neighbor 10.0.0.9 peer-group R 
  exit-address-family

Example: Configuration for Autonomous System 2 PE2

The following example shows how to configure PE2 in AS2 in a confederation topology: 


ip cef 
! 
ip vrf V1 
 rd 2:109 
 route-target export 1:100 
 route-target import 1:100 
! 
interface Loopback0 
 ip address 10.0.0.9 255.0.0.0 
 ip router isis 
! 
interface Loopback1 
 ip vrf forwarding V1 
 ip address 10.0.0.9 255.0.0.0 
! 
interface GigabitEthernet0/0/4
 no ip address 
 encapsulation frame-relay 
 frame-relay intf-type dce 
 no fair-queue 
 clockrate 2000000 
! 
interface GigabitEthernet0/0/4.1 point-to-point 
 description Bethel 
 ip vrf forwarding V1 
 ip unnumbered Loopback1 
 frame-relay interface-dlci 24 
! 
interface GigabitEthernet0/4/7 
 ip address 10.9.1.1 255.0.0.0 
 ip router isis 
 tag-switching ip 
! 
router ospf 10 vrf V1 
 log-adjacency-changes 
 redistribute bgp 2 subnets 
 network 10.0.0.2 255.0.0.0 area 0 
! 
router isis 
 net aa.0002.0000.0000.0009.00 
! 
router bgp 2 
 no synchronization 
 bgp log-neighbor-changes 
 bgp confederation identifier 100 
 neighbor 10.0.0.8 remote-as 2 
 neighbor 10.0.0.8 update-source Loopback0 
 ! 
 address-family ipv4 vrf V1 
  redistribute connected 
  redistribute ospf 10 
  no auto-summary 
  no synchronization 
  exit-address-family 
 !
 address-family vpnv4 
  neighbor 10.0.0.8 activate 
  neighbor 10.0.0.8 send-community extended 
  exit-address-family

Example: Configuration for Autonomous System 2 CE2

The following example shows how to configure CE2 in VPN1 in a confederation topology: 



interface Loopback0 
 ip address 10.0.0.11 255.0.0.0 
! 
interface GigabitEthernet0/0/7 
 no ip address 
 encapsulation frame-relay 
 no fair-queue 
 clockrate 2000000 
! 
interface GigabitEthernet0/0/7.1 point-to-point 
ip unnumbered Loopback0 
 frame-relay interface-dlci 24 
! 
router ospf 1 
 network 10.0.1.2 255.0.0.0 area 0

Additional References

Related Documents

Related Topic

Document Title

MPLS

MPLS Product Literature

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

RFC 1700

Assigned Numbers

RFC 1966

BGP Route Reflection: An Alternative to Full Mesh IBGP

RFC 2842

Capabilities Advertisement with BGP-4

RFC 2858

Multiprotocol Extensions for BGP-4

RFC 3107

Carrying Label Information in BGP-4

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

Technical support

Feature Information for MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 1. Feature Information for MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Feature Name

Releases

Feature Information

MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

Cisco IOS XE Release 3.13.0S

This feature was introduced on the Cisco ASR 920 Series Aggregation Services Router (ASR-920-12CZ-A, ASR-920-12CZ-D, ASR-920-4SZ-A, ASR-920-4SZ-D).