Broadband Access Aggregation and DSL Configuration Guide, Cisco IOS XE Release 3S

Remote Access MPLS-VPNs

The Remote Access MPLS-VPNs feature allows the service provider to offer a scalable end-to-end Virtual Private Network (VPN) service to remote users. This feature integrates the Multiprotocol Label Switching (MPLS)-enabled backbone with broadband access capabilities.

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 Remote Access MPLS-VPNs" section.

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Contents

•Prerequisites for Remote Access MPLS-VPNs

•Restrictions for Remote Access MPLS-VPNs

•Information About Remote Access MPLS-VPNs

•How to Configure Remote Access MPLS-VPNs

•Configuration Examples for Remote Access MPLS-VPNs

•Additional References

•Feature Information for Remote Access MPLS-VPNs

•Glossary

Prerequisites for Remote Access MPLS-VPNs

The Remote Access MPLS-VPNs feature has the following prerequisites:

•Your network must be running the following Cisco IOS XE services before you configure VPN operation:

–MPLS in the service provider backbone routers

–Tag Distribution Protocol (TDP) or the Label Distribution Protocol (LDP)

–Border Gateway Protocol (BGP) in all routers providing a VPN service

–Cisco Express Forwarding switching in each MPLS-enabled router

•The provider edge (PE) routers that belong to the same VPN must be configured with the same VPN ID. The VPN ID must be unique to the service provider network.

Restrictions for Remote Access MPLS-VPNs

The Remote Access MPLS-VPNs feature has the following restrictions:

•The VPN ID is not used to control the distribution of routing information or to associate IP addresses.

Information About Remote Access MPLS-VPNs

•Introduction to Remote Access MPLS-VPNs

•MPLS VPN Architecture

•PPP over Ethernet to MPLS VPN

Introduction to Remote Access MPLS-VPNs

MPLS-based VPNs allow service providers to deploy a scalable and cost-effective VPN service that provides a stable and secure path through the network. An enterprise connects to geographically dispersed sites in the Internet service provider's (ISPs) network through use of an MPLS backbone. Sites are interconnected to create an MPLS VPN.

The Remote Access MPLS-VPNs feature allows the service provider to offer a scalable end-to-end VPN service to remote users. The Remote Access MPLS-VPNs feature integrates the MPLS-enabled backbone with broadband access capabilities. By integrating access VPNs with MPLS VPNs, a service provider can:

•Enable remote users and offices to seamlessly access their corporate networks

•Offer equal access to a set of different ISPs or retail service providers

•Integrate their broadband access networks with the MPLS-enabled backbone

•Provide end-to-end VPN service to enterprise customers with remote access (RA) users and offices

•Separate network access and connectivity functions from ISP functions

MPLS VPN Architecture

MPLS VPN architecture enables the service provider to build the MPLS VPN network one time and add VPNs for new customers as needed, including them in the already established network. The elements that comprise the MPLS VPN are:

•Customer edge (CE) routers—The routers to which subscribers in a customer's network connect. The CE router connects to a service provider's edge router (PE router). The CE router initiates the remote access session to the PE router.

•Provider edge (PE) routers—The routers located at the edge of the service provider's MPLS core network. The PE router connects to one or more CE routers and has full knowledge of the routes to the VPNs associated with those CE routers. The PE router does not have knowledge of the routes to VPNs whose associated CE routers are not connected to it.

•Provider (P) routers—The service provider routers that comprise the provider's core network. The P routers do not assign VPN information and they do not have any knowledge of CE routers. Instead, the main focus of the P router is on label switching.

Figure 1 shows an example of MPLS VPN network architecture.

Figure 1 MPLS VPN Network—Example

PPP over Ethernet to MPLS VPN

Figure 2 shows the topology of integrated PPP over Ethernet (PPPoE) access to an MPLS VPN.

Figure 2 PPPoE Access to MPLS VPN Topology

In Figure 2, the service provider operates an MPLS VPN that interconnects all customer sites. The service provider's core network is an MPLS backbone with VPN service capability. The service provider provides all remote access operations to its customer. The network-side interfaces are tagged interfaces, logically separated into multiple VPNs.

Remote access is provided using a PPPoE connection. In this model, when a remote user attempts to establish a connection with a corporate network, a PPPoE session is initiated and is terminated on the service provider's virtual home gateway (VHG) or PE router. All remote hosts connected to a particular CE router must be part of the VPN to which the CE router is connected.

The PPPoE to MPLS VPN architecture is a flexible architecture with the following characteristics:

•A remote host can create multiple concurrent PPPoE sessions, each to a different VPN.

•If multiple remote hosts exist behind the same CE router, each remote host can log in to a different VPN.

•Any remote host can log in to any VPN at any time because each VHG or PE router has the VRFs for all possible VPNs preinstantiated on it. This configuration requires that the VRF be applied through the RADIUS server, which can cause scalability issues.

The following events occur as the VHG or PE router processes the incoming PPPoE session:

1. A PPPoE session is initiated over the broadband access network.

2. The VHG/PE router accepts and terminates the PPPoE session.

3. The VHG/PE router obtains virtual access interface (VAI) configuration information:

–The VHG/PE obtains a virtual template interface configuration information, which typically includes VRF mapping for sessions.

–The VHG/PE sends a separate request to either the customer's or service provider's RADIUS server for the VPN to authenticate the remote user.

–The VPN's VRF instance is instantiated on the VHG or PE. The VPN's VRF contains a routing table and other information associated with a specific VPN.

Typically, the customer RADIUS server is located within the customer VPN. To ensure that transactions between the VHG/PE router and the customer RADIUS server occur over routes within the customer VPN, the VHG/PE router is assigned at least one IP address that is valid within the VPN.

4. The VHG/PE router forwards accounting records to the service provider's proxy RADIUS server, which in turn logs the accounting records and forwards them to the appropriate customer RADIUS server.

5. The VHG/PE obtains an IP address for the CPE. The address is allocated from one of the following:

–Local address pool

–Service provider's RADIUS server, which either specifies the address pool or directly provides the address

–Service provider's DHCP server

6. The CPE is now connected to the customer VPN. Packets can flow to and from the remote user.

How to Configure Remote Access MPLS-VPNs

To configure the RA to MPLS VPN feature, perform the following configuration tasks:

•Configuring the MPLS Core Network (required)

•Configuring PPPoE (required)

•Configuring and Associating Virtual Private Networks (required)

Configuring the MPLS Core Network

The MPLS core network is configured by enabling label switching of IP packets on interfaces, configuring virtual routing and forwarding instances, associating VRFs and configuring Multiprotocol BGP PE-to-PE routing sessions. For details relating to these activities, see the appropriate section of the Cisco IOS XE Multiprotocol Label Switching Configuration Guide.

Configuring PPPoE

To configure PPPoE, perform the following configuration tasks:

•Configuring a Virtual Template Interface (required)

•Configuring PPPoE in a Broadband Aggregation Group (required)

Configuring a Virtual Template Interface

To create and configure a virtual template interface that can be configured and applied dynamically in creating virtual access interfaces, perform the steps in the following task.

SUMMARY STEPS

1. enable

2. configure terminal

3. interface virtual-template number

4. ip unnumbered ethernet number

5. ppp authentication chap

6. ppp ipcp address required

DETAILED STEPS

Configuring PPPoE in a Broadband Aggregation Group

To configure a broadband aggregation (BBA) group for PPPoE and to link it to the appropriate virtual template interface, perform the steps in the following task.

SUMMARY STEPS

1. enable

2. configure terminal

3. bba-group pppoe {name | global}

4. virtual-template template-number

5. sessions per-mac limit per-mac-limit

6. sessions max limit global pppoe session limit

7. exit

8. interface gigabitethernet slot/subslot/port.[subinterface]

9. encapsulation dot1q vlan-id

10. pppoe enable [group group-name]

DETAILED STEPS

interface gigabitethernet 
slot/subslot/port.[subinterface]

Configuring and Associating Virtual Private Networks

A Virtual Private Network (VPN) service can be added to your MPLS configuration by configuring VPNs and associating the VPNs with a virtual template interface. For details relating to these activities, see the Configuring MPLS Layer 3 VPNs module.

Configuration Examples for Remote Access MPLS-VPNs

This section provides the following configuration example:

•Example: Configuring Remote Access MPLS-VPNs with One VRF for PPPoE Sessions

Example: Configuring Remote Access MPLS-VPNs with One VRF for PPPoE Sessions

The following example shows how to configure the RA to MPLS VPN feature with one VRF for PPPoE sessions:

!

!Enables the AAA access control model.

aaa new-model

!

!Configures AAA accounting.

aaa authentication login default none

aaa authentication enable default none

aaa authentication ppp default group radius

aaa authorization config-commands

aaa authorization network default local

aaa session-id common

enable password cisco

!

username pppoe password 0 pppoe

username common password 0 common

!

!Creates the common VRF.

ip vrf common

rd 100:1000

route-target export 100:1000

route-target import 100:1000

!

!Specifies the BBA group to be used to establish PPPoE sessions and specifies the maximum

!number of PPPoE sessions to be established over a vlan.

bba-group pppoe

virtual-template 1

sessions per-mac limit 32000

!

no virtual-template snmp

!

!Configures the small buffer.

buffers small permanent 15000

!

!Defines the general loopback interface used for reachability to the router and as a

!source IP address for sessions (IBGP, TDP, and so on).

interface Loopback0

ip address 10.16.3.1 255.255.255.255

ip ospf network point-to-point 
!

!Creates a loopback interface in the vpn1 VRF. You do this for each customer VRF you IP

!unnumber interfaces to.

interface Loopback1

ip vrf forwarding vpn1

ip address 10.24.1.1 255.255.255.255

!

interface Loopback2

ip vrf forwarding vpn2

ip address 10.8.1.2 255.255.255.255

!

interface gigaethernet 0/0/0

load-interval 30

negotiation auto

no cdp enable

interface gigaethernet 0/0/0.9

encapsulation dot1q 9

pppoe enable

no cdp enable

!

!Enables label switching of IP packets on the interface.

interface GigabitEthernet1/0/0

ip address 10.1.10.1 255.255.0.0

no ip redirects

load-interval 30

negotiation auto

tag-switching ip

!

!Defines the virtual template and associates the common VRF with it.

interface Virtual-Template1

ip vrf forwarding common

ip unnumbered Loopback1

peer default ip address pool common

ppp authentication chap

!

!Configures OSPF to advertise the networks.

router ospf 100

log-adjacency-changes

auto-cost reference-bandwidth 1000

network 10.16.3.1 0.0.0.0 area 0

network 10.1.0.0 0.0.255.255 area 0

!

router rip

version 2

!

!Enters address family configuration mode to configure the VRF for PE to CE routing

!sessions.

address-family ipv4 vrf common

version 2

network 10.0.0.0

no auto-summary

exit-address-family

!

!Configures BGP to advertise the networks for the VPN.

router bgp 100

no synchronization

no bgp default ipv4-unicast

bgp log-neighbor-changes

neighbor 172.16.1.4 remote-as 100

neighbor 172.16.1.4 activate

!

!Enters address family configuration mode to configure the common VRF for PE to CE routing

!sessions.

address-family ipv4 vrf common

no auto-summary

no synchronization

aggregate-address 10.10.0.0 255.255.0.0 summary-only

exit-address-family

!

address-family vpnv4

neighbor 172.16.1.4 activate

neighbor 172.16.1.4 send-community both

exit-address-family

!

!Specifies the IP local pool to use for the VRF address assignment.

ip local pool common 10.10.1.1 10.10.126.0

ip classless

!Enters routing information in the routing table for the VRF.

ip route 10.0.0.0 255.0.0.0 FastEthernet0/0/0 10.9.0.1

ip route vrf common 10.22.0.0 255.255.0.0 Null0

ip route vrf common 10.30.0.0 255.255.0.0 2.1.1.1 3

ip route vrf common 10.32.0.0 255.255.0.0 2.2.151.1 2

ip route vrf common 10.33.0.0 255.255.0.0 2.3.101.1 2

no ip http server

ip pim bidir-enable

!

no cdp run

!

!Specifies the RADIUS host and configures RADIUS accounting. radius-server retransmit is

!on by default and cannot be removed.

radius-server host 10.19.100.150 auth-port 1645 acct-port 1646

radius-server retransmit 3

radius-server key test

radius-server authorization permit missing Service-Type

radius-server vsa send authentication

call admission limit 90

!

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for Remote Access MPLS-VPNs

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which 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 Table 1 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.

Glossary

CE—customer edge.

PPPoE—Point-to-Point Protocol over Ethernet.

PE—provider edge.

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