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Cisco IOS Software Releases 12.0 ST

Inter-Autonomous Systems for MPLS VPNs

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Table Of Contents

Inter-Autonomous Systems for MPLS VPNs

Feature Overview

Benefits

Routing Between Autonomous Systems

Exchanging VPN Routing Information

Packet Forwarding

Routing Between Sub-Autonomous Systems in a Confederation

Restrictions

Related Features and Technologies

Related Documents

Supported Platforms

Supported Standards, MIBs, and RFCs

Prerequisites

Configuration Tasks

Before You Begin

Configuring EBGP Routing for the Exchange of VPN Routes Between Autonomous Systems

Configuring EBGP Routing for the Exchange of VPN Routes Between Sub-Autonomous Systems in a Confederation

Displaying VPN-IPv4 LFIB Entries

Configuration Examples

Configuring EBGP Routing to Exchange VPN Routes Between Autonomous Systems

Configuration for Autonomous System 1, CE1

Configuration for Autonomous System 1, PE1

Configuration for Autonomous System 1, P1

Configuration for Autonomous System 1, EBGP1

Configuration for Autonomous System 2, EBGP2

Configuration for Autonomous System 2, P2

Configuration for Autonomous System 2, PE2

Configuration for Autonomous System 2, CE2

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

Configuration for Autonomous System 1, CE1

Configuration for Autonomous System 1, PE1

Configuration for Autonomous System 1, P1

Configuration for Autonomous System 1, EBGP1

Configuration for Autonomous System 2, EBGP2

Configuration for Autonomous System 2, P2

Configuration for Autonomous System 2, PE2

Configuration for Autonomous System 2, CE2

Command Reference

bgp default route-target filter

Glossary


Inter-Autonomous Systems for MPLS VPNs

This feature module explains how to provide MPLS VPN services that can span multiple autonomous systems (ASs) and VPN service providers. This document includes the following sections:

•Feature Overview

•Supported Platforms

•Supported Standards, MIBs, and RFCs

•Prerequisites

•Configuration Tasks

•Configuration Examples

•Command Reference

•Glossary

The following table lists the changes made to this document:

Release
Modification
12.1(5)T

This document was introduced.

12.0(16)ST

Added support for the Cisco 12000 series routers (Engine 0).

12.0(17)ST

Added support for the Cisco 12000 series routers (Engine 2).


Feature Overview

The inter-autonomous system for MPLS VPNs feature allows an MPLS VPN to span service providers and autonomous systems.

As VPNs grow, their requirements expand. In some cases, VPNs need to reside on different autonomous systems in different geographic areas. (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.) 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.

The inter-autonomous systems for MPLS VPNs feature provides that seamless integration of autonomous systems and service providers. 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 systems' border edge routers use exterior border gateway protocol (EBGP) to exchange that 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.

An MPLS VPN with inter-autonomous system support allows a service provider to provide to customers scalable Layer 3 VPN services, such as web hosting, application hosting, interactive learning, electronic commerce, and telephony service. A VPN service provider supplies a secure, IP-based network that shares resources on one or more physical networks.

The primary function of a EBGP is to exchange network reachability information between autonomous systems, including information about the list of autonomous system routes. The autonomous systems use EGBP border edge routers to distribute the routes, which include label switching information. Each border edge router rewrites the next-hop and MPLS labels. See the section "Routing Between Autonomous Systems" for more information.

Inter-autonomous system configurations supported in an MPLS VPN can include:

•Interprovider VPN—MPLS VPNs that include two or more autonomous systems, connected by separate border edge routers. The autonomous systems exchange routes using EBGP. No interior gateway protocol (IGP) or routing information is exchanged between the autonomous systems.

•BGP Confederations — MPLS VPNs that divide a single autonomous system into multiple sub-autonomous 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.

Benefits

The inter-autonomous system MPLS VPN feature provides the following benefits:

Allows a VPN to Cross More Than One Service Provider Backbone

The inter-autonomous systems for MPLS VPNs feature allows service providers, running separate autonomous systems, to jointly offer MPLS VPN services to the same end 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. Previous MPLS VPN could only traverse a single BGP autonomous system service provider backbone. The inter-autonomous system 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

The inter-autonomous systems for MPLS VPNs feature allows a service provider to 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 IBGP Meshing

The inter-autonomous systems MPLS VPNs feature can make IBGP meshing in an autonomous system more organized and manageable. You can divide an autonomous system into multiple, separate sub-autonomous 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 NLRI between the sub-autonomous systems that form the confederation.

Routing Between Autonomous Systems

Figure 1 illustrates one MPLS VPN consisting of two separate autonomous systems. Each autonomous system operates under different administrative control and runs a different IGP. Service providers exchange routing information through EBGP border edge routers (ASBR1, ASBR2).

Figure 1 EBGP Connection Between Two Autonomous Systems

This configuration uses the following process to transmit information:

Step 1 The provider edge router (PE-1) assigns a label for a route before distributing that route. The PE router uses the multiprotocol extensions of a border gateway protocol (BGP) to transmit label mapping information. The PE router distributes the route as an VPN-IPv4 address. The address label and the VPN identifier are encoded as part of the NLRI.

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

Step 3 The EBGP border edge router (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:

•That the next hop router is always reachable in the service provider (P) backbone network.

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

Step 4 The EBGP border edge router (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 on.

•If the IBGP neighbors are not configured with the neighbor next-hop-self command, the next hop address does not get changed. 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 routers in different autonomous systems.

Exchanging VPN Routing Information

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

Figure 2 illustrates the exchange of VPN route and label information between autonomous systems. The autonomous systems use the following guidelines to exchange VPN routing information:

•Routing information includes:

–The destination network (N)

–The next hop field associated with the distributing router

–A local MPLS label (L)

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

•The ASBRs are configured to change the next hop (next-hop-self) when sending VPN-IPv4 NLRIs to the 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 Autonomous Systems in an Interprovider VPN Network

Figure 3 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 the configured to change the next hop address.

Figure 3 Exchanging Routes and Labels Between Autonomous Systems in an Interprovider VPN Network

Packet Forwarding

Figure 4 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 MPLS. Packets use the routing information stored in the LFIB of each PE router and EBGP border edge router.

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

Each autonomous system uses standard multi-level labeling to forward packets between the edges of the autonomous system routers (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 router or EBGP border edge router. (For example, the IGP label of ASBR2 points to the ASBR2 border edge router.)

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

Figure 4 Forwarding Packets Between Autonomous Systems in an Interprovider VPN Network

Figure 5 illustrates shows the same packet forwarding method, except the EBGP router (ASBR1) forwards the packet without reassigning it a new label.

Figure 5 Forwarding Packets Between Autonomous Systems in an Interprovider VPN Network

Routing Between Sub-Autonomous Systems in a Confederation

A VPN can span service providers running in separate autonomous systems or between multiple sub-autonomous systems that have been grouped together to form a confederation.

A confederation reduces the total number of peer devices in an autonomous system. A confederation divides an autonomous system into sub-autonomous systems and assigns a confederation identifier to the autonomous systems.

In a confederation, each sub-autonomous system is fully meshed with other sub-autonomous systems. The sub-autonomous systems communicate using an IGP, such as Open Shortest Path First (OSPF) or Intermediate System-to-Intermediate System (IS-IS). Each sub-autonomous system also has an EBGP connection to the other sub-autonomous systems. The confederation EBGP (CEBGP) border edge routers forward next-hop-self addresses between the specified sub-autonomous systems. The next-hop-self address forces the 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 sub-autonomous systems in two ways:

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

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

Note Figure 2 and Figure 3 illustrate how two autonomous systems exchange routes and forward packets. Sub-autonomous systems in a confederation use a similar method of exchanging routes and forwarding packets.

Figure 6 illustrates a typical MPLS VPN confederation configuration. In this confederation configuration:

•The two CEBGP border edge routers exchange VPN-IPv4 addresses with labels between the two sub-autonomous systems.

•The distributing router 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 Sub-Autonomous Systems in a Confederation

In this confederation configuration:

•CEBGP border edge routers function as neighboring peers between the sub-autonomous systems. The sub-autonomous systems use EBGP to exchange route information.

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

•Each PE and CEBGP border edge router assigns its own label to each VPN-IPv4 address prefix before redistributing the routes. The CEBGP border edge routers 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 sub-autonomous systems, the CEBGP border edge router address is distributed throughout the IBGP neighbors and the two CEBGP border edge routers are known to both confederations.

Restrictions

A VPN-IPv4 EBGP session must be configured between directly connected ASBRs. Multihop VPN-IPv4 EBGP is not supported.

Related Features and Technologies

The Inter-Autonomous Systems for MPLS VPNs feature is used with the VPN capabilities of MPLS. MPLS VPNs were introduced in IOS Release 12.0(5)T.

Related Documents

•MPLS Virtual Private Network Feature Module

•MPLS Virtual Private Network Enhancements Feature Module

•Cisco IOS Switching Services Configuration Guide (Release 12.2), Multiprotocol Label Switching

Supported Platforms

The following router platforms are supported at the service provider edge:

•Cisco 7200 series

•Cisco 7500 series

•Cisco 12000 series (Engine 0 and Engine 2)

Supported Standards, MIBs, and RFCs

MIBs

No new or modified MIBs are supported by this feature.

RFCs

•RFC 1771, A Border Gateway Protocol 4

•RFC1965, Autonomous System Confederation for BGP

•RFC 1164, Application of the Border Gateway Protocol in the Internet

•RFC 2842, Capabilities Advertisement with BGP-4

•RFC 2283, Multiprotocol Extensions for BGP-4

•RFC 2547, BGP/MPLS VPNs

Standards

•Internet draft draft-ramachandra-bgp-ext-communities-08.txt, BGP Extended Community Attribute

Prerequisites

The network must be properly configured for MPLS VPN operation before you configure inter-autonomous systems. Refer to the following documents for MPLS VPN network configuration details:

•MPLS Virtual Private Network Feature Module

•MPLS Virtual Private Network Enhancements Feature Module

•Cisco IOS Switching Services Configuration Guide (Release 12.2).

Configuration Tasks

To configure the exchange of VPN-IPv4 addresses between two or more autonomous systems or sub-autonomous systems in a confederation, perform the following tasks:

•Configuring EBGP Routing for the Exchange of VPN Routes Between Autonomous Systems

•Configuring EBGP Routing for the Exchange of VPN Routes Between Sub-Autonomous Systems in a Confederation

•Displaying VPN-IPv4 LFIB Entries

Before You Begin

Before you configure EBGP routing between autonomous systems or sub-autonomous systems in an 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 (as appropriate to the existing network configuration) the following tasks as described in the Cisco IOS Switching Services Configuration Guide (the Configuring Multiprotocol Label Switching chapter).

•Define VPN routing instances

•Configure BGP routing sessions in the service provider (P) network

•Configure PE to PE routing sessions in the service provider (P) network

•Configure BGP PE to CE routing sessions

Configuring EBGP Routing for the Exchange of VPN Routes Between Autonomous Systems

Use the following procedure to configure an EBGP border edge router in an autonomous system to exchange VPN routes with another autonomous system.

Note Issue the redistribute connected subnets command in the IGP configuration portion of the router to propagates host routes for VPN-IPv4 EBGP neighbors to other routers and provider edge routers. Alternatively, you can specify the next-hop-self address when you configure IBGP neighbors.

 
Command
Purpose

Step 1 

Router# configure terminal

Enters the global configuration mode.

Step 2 

Router(config)# router bgp autonomous-system

Creates an EBGP routing process and assigns it an AS number. The autonomous system number is passed along to identify the router to EBGP routers in another autonomous system.

Step 3 

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

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

Step 4 

Router(config-router)# address-family vpnv4[unicast]

Configures a routing session to carry VPN-IPv4 addresses across the VPN backbone. Each address has been made globally unique by the addition of an 8-byte route distinguisher (RD). Unicast is optional; use it if you need to specify a unicast prefix.

Step 5 

Router(config-router-af)# neighbor peer-group-name remote-as autonomous-system

Enters the address family submode and specifies a neighboring EBGP peer group. This EBGP peer group is identified to the specified autonomous system.

Step 6 

Router(config-router-af)# neighbor peer-group-name activate

Activates the advertisement of the VPN-IPv4 address family to a neighboring EBGP router.

Step 7 

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

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

Configuring EBGP Routing for the Exchange of VPN Routes Between Sub-Autonomous Systems in a Confederation

Use the following procedure to configure EBGP border edge router in a confederation to exchange VPN routes with another sub-autonomous system.

Notes:

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

•In this confederation, sub-autonomous 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 routers in the sub-autonomous system are distributed throughout the network, not just the addresses of CEBGP-1 and CEBGP-2.

 
Command
Purpose

Step 1 

Router# configure terminal

Enters the global configuration mode.

Step 2 

Router(config)# router bgp sub-autonomous-system

Creates an EBGP routing process and assigns it an AS number. The sub-autonomous system number is passed along to identify the router to EBGP routers in other sub-autonomous systems.

Step 3 

Router(config)# bgp confederation identifier autonomous-system

Defines an EBGP confederation by specifying a confederation identifier associated with each sub-autonomous system. The sub-autonomous systems appear as a single autonomous system.

Step 4 

Router(config)# bgp confederation peers sub-autonomous-systems

Specifies the sub-autonomous systems that belong to the confederation (identifying neighbors from other sub-autonomous systems within the confederation as special EBGP peers).

Step 5 

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

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

Step 6 

Router(config-router)# address-family vpnv4[unicast]

Configures a routing session to carry VPN-IPv4 addresses across the VPN backbone. Each address has been made globally unique by the addition of an 8-byte route distinguisher (RD). Unicast is optional; use it if you need to specify a unicast prefix.

Step 7 

Router(config-router-af)# neighbor peer-group-name remote-as autonomous-system

Enters the address family submode and specifies a neighboring EBGP peer group. This EBGP peer group is identified to the specified sub-autonomous system.

Step 8 

Router(config-router-af)# neighbor peer-group-name next-hop-self

Advertises the router as the next hop for the specified neighbor. If you specify a next-hop-self address as part of the router configuration, you do not need to use the redistribute connected command

Step 9 

Router(config-router-af)# neighbor peer-group-name activate

Activates the advertisement of the VPN-IPv4 address family to a neighboring PE router in the specified sub-autonomous system.

Step 10 

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

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

Displaying VPN-IPv4 LFIB Entries

Use the following procedure to display the VPN-IPv4 Label Forwarding Information Base (LFIB) entries at the border edge routers in the autonomous systems:

 
Command
Purpose

Step 1  

Router# show ip bgp vpnv4 all [tags]

Displays information about all VPN-IPv4 labels.

Step 2  

Router# show tag-switching forwarding-table

Displays the contents of the LFIB (such as VPN-IPv4 prefix/length and BGP next hop destination for the route).

The following is an example of how the VPN-IPv4 LFIB entries appear when you use the show tag-switching forwarding-table privileged EXEC command:

Router# show tag-switching forwarding-table 

Local Outgoing      Prefix            Bytes tag Outgoing       Next Hop       

tag   tag or VC     or Tunnel Id      switched  interface                     

33    33            10.120.4.0/24     0         Hs0/0         point2point    

35    27            100:12:10.200.0.1/32 \         

                                      0         Hs0/0         point2point

Note In this example, the Prefix field appears as a VPN-IPv4 route distinguisher (RD), plus the prefix. If the value is longer than the Prefix column (as illustrated in the last line of the example), the output automatically wraps onto the next line in the forwarding table to preserve column alignment.

Configuration Examples

This section provides the following configuration examples:

•Configuring EBGP Routing to Exchange VPN Routes Between Autonomous Systems

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

Configuring EBGP Routing to Exchange VPN Routes Between Autonomous Systems

The network topology in Figure 7 shows two autonomous systems, which are configured as follows:

•Autonomous system 1 (AS1) includes PE1, P1, EBGP1. The IGP is OSPF.

•Autonomous system 2 (AS2) includes PE2, P2, EBGP2. The IGP is ISIS.

•CE1 and CE2 belongs to the same VPN, which is called VPN1.

•The P routers 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

Configuration for Autonomous System 1, CE1 

CE1: Burlington 

! 

interface Loopback1 

 ip address 1.0.0.6 255.255.255.255 

! 

interface Serial1/3 

 description Veritas 

 no ip address 

 encapsulation frame-relay 

 frame-relay intf-type dce 

! 

interface Serial1/3.1 point-to-point 

 description Veritas 

 ip address 1.6.2.1 255.255.255.252 

 frame-relay interface-dlci 22 

! 

router ospf 1 

 network 1.0.0.0 0.255.255.255 area 0

Configuration for Autonomous System 1, PE1 

PE1: Veritas 

! 

ip cef 

! 

ip vrf V1 

 rd 1:105 

 route-target export 1:100 

 route-target import 1:100 

! 

interface Serial0/0 

 description Burlington 

 no ip address 

 encapsulation frame-relay 

 no fair-queue 

 clockrate 2000000 

! 

interface Serial0/0.3 point-to-point 

 description Burlington 

 ip vrf forwarding V1 

 ip address 1.6.2.2 255.255.255.252 

 frame-relay interface-dlci 22 

! 

interface Ethernet0/1 

 description Vermont 

 ip address 100.2.2.5 255.255.255.0 

 tag-switching ip 

! 

router ospf 1 

 log-adjacency-changes 

 network 100.0.0.0 0.255.255.255 area 0 

! 

router ospf 10 vrf V1 

 log-adjacency-changes 

 redistribute bgp 1 metric 100 subnets 

 network 1.0.0.0 0.255.255.255 area 0 

! 

router bgp 1 

 no synchronization 

 neighbor R peer-group 

 neighbor R remote-as 1 

 neighbor R update-source Loopback0 

 neighbor 100.0.0.2 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 100.0.0.2 peer-group R 

 no auto-summary 

 exit-address-family

Configuration for Autonomous System 1, P1 

P1: Vermont 

! 

ip cef 

! 

interface Loopback0 

 ip address 100.0.0.2 255.255.255.255 

! 

interface Ethernet0/1 

 description Ogunquit 

 ip address 100.2.1.1 255.255.255.0 

 tag-switching ip 

! 

interface FastEthernet2/0 

 description Veritas 

 ip address 100.2.2.1 255.255.255.0 

 duplex auto 

 speed auto 

 tag-switching ip 

! 

router ospf 1 

 log-adjacency-changes 

 network 100.0.0.0 0.255.255.255 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 100.0.0.4 peer-group R 

 neighbor 100.0.0.5 peer-group R 

 ! 

 address-family vpnv4 

 neighbor R activate 

 neighbor R route-reflector-client 

 neighbor R send-community extended 

 neighbor 100.0.0.4 peer-group R 

 neighbor 100.0.0.5 peer-group R 

 exit-address-family

Configuration for Autonomous System 1, EBGP1 

EBGP1: Ogunquit 

! 

ip cef 

! 

interface Loopback0 

 ip address 100.0.0.4 255.255.255.255 

! 

interface Ethernet0/1 

 description Vermont 

 ip address 100.2.1.40 255.255.255.0 

 tag-switching ip 

! 

interface ATM1/0 

 description Lowell 

 no ip address 

 no atm scrambling cell-payload 

 no atm ilmi-keepalive 

! 

interface ATM1/0.1 point-to-point 

 description Lowell 

 ip address 12.0.0.1 255.255.255.252 

 pvc 1/100 

! 

router ospf 1 

 log-adjacency-changes 

 redistribute connected subnets 

 network 100.0.0.0 0.255.255.255 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 12.0.0.2 remote-as 2 

 neighbor 100.0.0.2 peer-group R 

 no auto-summary 

 ! 

 address-family vpnv4 

 neighbor R activate 

 neighbor R send-community extended 

 neighbor 12.0.0.2 activate 

 neighbor 12.0.0.2 send-community extended 

 neighbor 100.0.0.2 peer-group R 

 no auto-summary 

 exit-address-family

Configuration for Autonomous System 2, EBGP2 

EBGP2: Lowell 

! 

ip cef 

! 

ip vrf V1 

 rd 2:103 

 route-target export 1:100 

 route-target import 1:100 

! 

interface Loopback0 

 ip address 200.0.0.3 255.255.255.255 

 ip router isis 

! 

interface Loopback1 

 ip vrf forwarding V1 

 ip address 1.0.0.3 255.255.255.255 

! 

interface Serial0/0 

 description Littleton 

 no ip address 

 encapsulation frame-relay 

 load-interval 30 

 no fair-queue 

 clockrate 2000000 

! 

interface Serial0/0.2 point-to-point 

 description Littleton 

 ip unnumbered Loopback0 

 ip router isis 

 tag-switching ip 

 frame-relay interface-dlci 23 

! 

interface ATM1/0 

 description Ogunquit 

 no ip address 

 atm clock INTERNAL 

 no atm scrambling cell-payload 

 no atm ilmi-keepalive 

! 

interface ATM1/0.1 point-to-point 

 description Ogunquit 

 ip address 12.0.0.2 255.255.255.252 

 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 12.0.0.1 remote-as 1 

 neighbor 200.0.0.8 remote-as 2 

 neighbor 200.0.0.8 update-source Loopback0 

 neighbor 200.0.0.8 next-hop-self 

 ! 

address-family ipv4 vrf V1 

 redistribute connected 

 no auto-summary 

 no synchronization 

 exit-address-family 

 ! 

address-family vpnv4 

 neighbor 12.0.0.1 activate 

 neighbor 12.0.0.1 send-community extended 

 neighbor 200.0.0.8 activate 

 neighbor 200.0.0.8 next-hop-self 

 neighbor 200.0.0.8 send-community extended 

 exit-address-family

Configuration for Autonomous System 2, P2 

P2: Littleton 

! 

ip cef 

! 

ip vrf V1 

 rd 2:108 

 route-target export 1:100 

 route-target import 1:100 

! 

interface Loopback0 

 ip address 200.0.0.8 255.255.255.255 

 ip router isis 

! 

interface Loopback1 

 ip vrf forwarding V1 

 ip address 1.0.0.8 255.255.255.255 

! 

interface FastEthernet0/0 

 description Pax 

 ip address 200.9.1.2 255.255.255.0 

 ip router isis 

 tag-switching ip 

! 

interface Serial5/0 

 description Lowell 

 no ip address 

 encapsulation frame-relay 

 frame-relay intf-type dce 

! 

interface Serial5/0.1 point-to-point 

 description Lowell 

 ip unnumbered Loopback0 

 ip router isis 

 tag-switching ip 

 frame-relay interface-dlci 23 

! 

router isis 

 net 49.0002.0000.0000.0008.00 

! 

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 200.0.0.3 peer-group R 

 neighbor 200.0.0.9 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 200.0.0.3 peer-group R 

 neighbor 200.0.0.9 peer-group R 

 exit-address-family

Configuration for Autonomous System 2, PE2 

PE2: Pax 

! 

ip cef 

! 

ip vrf V1 

 rd 2:109 

 route-target export 1:100 

 route-target import 1:100 

! 

interface Loopback0 

 ip address 200.0.0.9 255.255.255.255 

 ip router isis 

! 

interface Loopback1 

 ip vrf forwarding V1 

 ip address 1.0.0.9 255.255.255.255 

! 

interface Serial0/0 

 description Bethel 

 no ip address 

 encapsulation frame-relay 

 frame-relay intf-type dce 

 no fair-queue 

 clockrate 2000000 

! 

interface Serial0/0.1 point-to-point 

 description Bethel 

 ip vrf forwarding V1 

 ip unnumbered Loopback1 

 frame-relay interface-dlci 24 

! 

interface FastEthernet0/1 

 description Littleton 

 ip address 200.9.1.1 255.255.255.0 

 ip router isis 

 tag-switching ip 

! 

router ospf 10 vrf V1 

 log-adjacency-changes 

 redistribute bgp 2 subnets 

 network 1.0.0.0 0.255.255.255 area 0 

! 

router isis 

 net 49.0002.0000.0000.0009.00 

! 

router bgp 2 

 no synchronization 

 bgp log-neighbor-changes 

 neighbor 200.0.0.8 remote-as 2 

 neighbor 200.0.0.8 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 200.0.0.8 activate 

 neighbor 200.0.0.8 send-community extended 

 exit-address-family

Configuration for Autonomous System 2, CE2 

CE2: Bethel 

! 

interface Loopback0 

 ip address 1.0.0.11 255.255.255.255 

! 

interface Serial0 

 description Pax 

 no ip address 

 encapsulation frame-relay 

 no fair-queue 

 clockrate 2000000 

! 

interface Serial0.1 point-to-point 

 description Pax 

 ip unnumbered Loopback0 

 frame-relay interface-dlci 24 

! 

router ospf 1 

 network 1.0.0.0 0.255.255.255 area 0

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

The network topology in Figure 8 shows a single internet service provider (ISP), which is partitioning the backbone with confederations. The AS number of the provider is 100. The two autonomous systems run their own IGPs and are configured as follows:

•Autonomous system 1 (AS1) includes PE1, P1, EBGP1. The IGP is OSPF.

•Autonomous system 2 (AS2) includes PE2, P2, EBGP2. The IGP is ISIS.

•CE1 and CE2 belongs to the same VPN, which is called VPN1.

•The P routers are route reflectors.

•EBGP1 is configured with the redistribute connected subnets command.

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

Figure 8 Configuring Two Autonomous Systems in a Confederation

Configuration for Autonomous System 1, CE1 

CE1: Burlington 

! 

interface Loopback1 

 ip address 1.0.0.6 255.255.255.255 

! 

interface Serial1/3 

 description Veritas 

 no ip address 

 encapsulation frame-relay 

 frame-relay intf-type dce 

! 

interface Serial1/3.1 point-to-point 

 description Veritas 

 ip address 1.6.2.1 255.255.255.252 

 frame-relay interface-dlci 22 

! 

router ospf 1 

 network 1.0.0.0 0.255.255.255 area 0

Configuration for Autonomous System 1, PE1 

PE1: Veritas 

! 

ip cef 

! 

ip vrf V1 

 rd 1:105 

 route-target export 1:100 

 route-target import 1:100 

! 

interface Serial0/0 

 description Burlington 

 no ip address 

 encapsulation frame-relay 

 no fair-queue 

 clockrate 2000000 

! 

interface Serial0/0.3 point-to-point 

 description Burlington 

 ip vrf forwarding V1 

 ip address 1.6.2.2 255.255.255.252 

 frame-relay interface-dlci 22 

! 

interface Ethernet0/1 

 description Vermont 

 ip address 100.2.2.5 255.255.255.0 

 tag-switching ip 

! 

router ospf 1 

 log-adjacency-changes 

 network 100.0.0.0 0.255.255.255 area 0 

! 

router ospf 10 vrf V1 

 log-adjacency-changes 

 redistribute bgp 1 metric 100 subnets 

 network 1.0.0.0 0.255.255.255 area 0 

! 

router bgp 1 

no synchronization 

bgp confederation identifier 100 

bgp confederation identifier 100 

neighbor R peer-group 

neighbor R remote-as 1 

neighbor R update-source Loopback0 

neighbor 100.0.0.2 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 100.0.0.2 peer-group R 

 no auto-summary 

 exit-address-family

Configuration for Autonomous System 1, P1 

P1: Vermont 

! 

ip cef 

! 

interface Loopback0 

 ip address 100.0.0.2 255.255.255.255 

! 

interface Ethernet0/1 

 description Ogunquit 

 ip address 100.2.1.1 255.255.255.0 

 tag-switching ip 

! 

interface FastEthernet2/0 

 description Veritas 

 ip address 100.2.2.1 255.255.255.0 

 duplex auto 

 speed auto 

 tag-switching ip 

! 

router ospf 1 

 log-adjacency-changes 

 network 100.0.0.0 0.255.255.255 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 100.0.0.4 peer-group R 

neighbor 100.0.0.5 peer-group R 

 ! 

 address-family vpnv4 

 neighbor R activate 

 neighbor R route-reflector-client 

 neighbor R send-community extended 

 neighbor 100.0.0.4 peer-group R 

 neighbor 100.0.0.5 peer-group R 

 exit-address-family

Configuration for Autonomous System 1, EBGP1 

EBGP1: Ogunquit 

! 

ip cef 

! 

interface Loopback0 

 ip address 100.0.0.4 255.255.255.255 

! 

interface Ethernet0/1 

 description Vermont 

 ip address 100.2.1.40 255.255.255.0 

 tag-switching ip 

! 

interface ATM1/0 

 description Lowell 

 no ip address 

 no atm scrambling cell-payload 

 no atm ilmi-keepalive 

! 

interface ATM1/0.1 point-to-point 

 description Lowell 

 ip address 12.0.0.1 255.255.255.252 

 pvc 1/100 

! 

router ospf 1 

 log-adjacency-changes 

 redistribute connected subnets 

 network 100.0.0.0 0.255.255.255 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 12.0.0.2 remote-as 2 

neighbor 12.0.0.2 next-hop-self 

neighbor 100.0.0.2 peer-group R 

no auto-summary 

 ! 

 address-family vpnv4 

neighbor R activate 

neighbor R send-community extended 

neighbor 12.0.0.2 activate 

neighbor 12.0.0.2 next-hop-self 

neighbor 12.0.0.2 send-community extended 

neighbor 100.0.0.2 peer-group R 

no auto-summary 

exit-address-family

Configuration for Autonomous System 2, EBGP2 

EBGP2: Lowell 

! 

ip cef 

! 

ip vrf V1 

 rd 2:103 

 route-target export 1:100 

 route-target import 1:100 

! 

interface Loopback0 

 ip address 200.0.0.3 255.255.255.255 

 ip router isis 

! 

interface Loopback1 

 ip vrf forwarding V1 

 ip address 1.0.0.3 255.255.255.255 

! 

interface Serial0/0 

 description Littleton 

 no ip address 

 encapsulation frame-relay 

 load-interval 30 

 no fair-queue 

 clockrate 2000000 

! 

interface Serial0/0.2 point-to-point 

 description Littleton 

 ip unnumbered Loopback0 

 ip router isis 

 tag-switching ip 

 frame-relay interface-dlci 23 

! 

interface ATM1/0 

 description Ogunquit 

 no ip address 

 atm clock INTERNAL 

 no atm scrambling cell-payload 

 no atm ilmi-keepalive 

! 

interface ATM1/0.1 point-to-point 

 description Ogunquit 

 ip address 12.0.0.2 255.255.255.252 

 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 

bgp confederation identifier 100 

bgp confederation peers 1 

neighbor 12.0.0.1 remote-as 1 

neighbor 12.0.0.1 next-hop-self 

neighbor 200.0.0.8 remote-as 2 

neighbor 200.0.0.8 update-source Loopback0 

neighbor 200.0.0.8 next-hop-self 

 ! 

address-family ipv4 vrf V1 

 redistribute connected 

 no auto-summary 

 no synchronization 

 exit-address-family 

 ! 

address-family vpnv4 

neighbor 12.0.0.1 activate 

neighbor 12.0.0.1 next-hop-self 

neighbor 12.0.0.1 send-community extended 

neighbor 200.0.0.8 activate 

neighbor 200.0.0.8 next-hop-self 

neigh