MPLS VPN Half-Duplex VRF
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MPLS VPN Half-Duplex VRFLast Updated: June 6, 2012
The MPLS VPN Half-Duplex VRF feature provides scalable hub-and-spoke connectivity for subscribers of an Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) service. This feature addresses the limitations of hub-and-spoke topologies by removing the requirement of one virtual routing and forwarding (VRF) instance per spoke. This feature also ensures that subscriber traffic always traverses the central link between the wholesale service provider and the Internet service provider (ISP), whether the subscriber traffic is being routed to a remote network by way of the upstream ISP or to another locally or remotely connected subscriber.
Finding Feature InformationYour 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 Table at the end of this document. 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. Restrictions for MPLS VPN Half-Duplex VRFThe following features are not supported on interfaces configured with the MPLS VPN Half-Duplex VRF feature:
Information About Configuring MPLS VPN Half-Duplex VRFMPLS VPN Half-Duplex VRF OverviewThe MPLS VPN Half-Duplex VRF feature provides:
The figure below shows a sample hub-and-spoke topology. Upstream and Downstream VRFsThe MPLS VPN Half-Duplex VRF feature uses two unidirectional VRFs to forward IP traffic between the spokes and the hub PE router:
The spoke PE router redistributes routes from the downstream VRF into Multiprotocol Border Gateway Protocol (MP-BGP). That router typically advertises a summary route across the MPLS core for the connected spokes. The VRF configured on the hub PE router imports the advertised summary route. Reverse Path Forwarding CheckThe Reverse Path Forwarding (RPF) check ensures that an IP packet that enters a router uses the correct inbound interface. The MPLS VPN Half-Duplex VRF feature supports unicast RPF check on the spoke-side interfaces. Because different VRFs are used for downstream and upstream forwarding, the RPF mechanism ensures that source address checks occur in the downstream VRF. Unicast RPF is not on by default. You need to enable it, as described in Configuring Unicast Reverse Path Forwarding . How to Configure MPLS VPN Half-Duplex VRF
Configuring the Upstream and Downstream VRFs on the Spoke PE RouterSUMMARY STEPS
DETAILED STEPS Associating a VRF with an Interface
SUMMARY STEPS
DETAILED STEPS
Configuring the Downstream VRF for an AAA ServerTo configure the downstream VRF for an AAA (RADIUS) server in broadband or remote access situations, enter the following Cisco attribute value: lcp:interface-config=ip vrf forwarding U downstream D In standard VPN situations, enter instead the following Cisco attribute value: ip:vrf-id=U downstream D Verifying MPLS VPN Half-Duplex VRF Configuration
SUMMARY STEPS
DETAILED STEPS
Configuration Examples for MPLS VPN Half-Duplex VRF
Example Configuring the Upstream and Downstream VRFs on the Spoke PE RouterThe following example configures an upstream VRF named Up: Router> enable Router# configure terminal Router(config)# vrf definition Up Router(config-vrf)# rd 1:0 Router(config-vrf)# address-family ipv4 Router(config-vrf-af)# route-target import 1:0 Router(config-vrf-af)# exit-address-family The following example configures a downstream VRF named Down: Router> enable Router# configure terminal Router(config)# vrf definition Down Router(config-vrf)# rd 1:8 Router(config-vrf)# address-family ipv4 Router(config-vrf-af)# route-target import 1:8 Router(config-vrf-af)# exit-address-family Example Associating a VRF with an InterfaceThe following example associates the VRF named Up with POS 3/0/1 subinterface and specifies the downstream VRF named Down: Router> enable Router# configure terminal Router(config)# interface POS 3/0/1 Router(config-if)# vrf forwarding Up downstream Down Router(config-if)# ip address 10.0.0.1 255.0.0.0 Example Configuring MPLS VPN Half-Duplex VRF Using Static CE-PE RoutingThis example uses the hub-and-spoke topology shown in the figure below with local authentication (that is, the RADIUS server is not used): vrf definition D rd 1:8 address-family ipv4 route-target export 1:100 exit-address-family ! vrf definition U rd 1:0 address-family ipv4 route-target import 1:0 exit-address-family ! ip cef vpdn enable ! vpdn-group U accept-dialin protocol pppoe virtual-template 1 ! interface Loopback 2 vrf forwarding U ip address 10.0.0.8 255.255.255.255 ! interface ATM 2/0 description Mze ATM3/1/2 no ip address no atm ilmi-keepalive pvc 0/16 ilmi ! pvc 3/100 protocol pppoe ! pvc 3/101 protocol pppoe ! Example Configuring MPLS VPN Half-Duplex VRF Using RADIUS Server and Static CE-PE RoutingThe following example shows how to connect two Point-to-Point Protocol over Ethernet (PPPoE) clients to a single VRF pair on the spoke PE router named Router C. Although both PPPoE clients are configured in the same VRF, all communication occurs using the hub PE router. Half-duplex VRFs are configured on the spoke PE. The client configuration is downloaded to the spoke PE from the RADIUS server. This example uses the hub-and-spoke topology shown in the figure above.
aaa new-model ! aaa group server radius R server 10.0.20.26 auth-port 1812 acct-port 1813 ! aaa authentication ppp default group radius aaa authorization network default group radius ! vrf defintion D description Downstream VRF - to spokes rd 1:8 address-family ipv4 route-target export 1:100 exit-address-family ! vrf definition U description Upstream VRF - to hub rd 1:0 address-family ipv4 route-target import 1:0 exit-address-family ! ip cef vpdn enable ! vpdn-group U accept-dialin protocol pppoe virtual-template 1 ! interface Loopback2 vrf forwarding U ip address 10.0.0.8 255.255.255.255 ! interface ATM2/0 pvc 3/100 protocol pppoe ! pvc 3/101 protocol pppoe ! interface virtual-template 1 no ip address ppp authentication chap ! router bgp 1 no synchronization neighbor 172.16.0.34 remote-as 1 neighbor 172.16.0.34 update-source Loopback0 no auto-summary ! address-family vpnv4 neighbor 172.16.0.34 activate neighbor 172.16.0.34 send-community extended auto-summary exit-address-family ! address-family ipv4 vrf U no auto-summary no synchronization exit-address-family ! address-family ipv4 vrf D redistribute static no auto-summary no synchronization exit-address-family ! ip local pool U-pool 10.8.1.1 2.8.1.100 ip route vrf D 10.0.0.0 255.0.0.0 Null0 ! radius-server host 10.0.20.26 auth-port 1812 acct-port 1813 radius-server key cisco Example Configuring MPLS VPN Half-Duplex VRF Using Dynamic CE-PE RoutingThe following example shows how to use OSPF to dynamically advertise the routes on the spoke sites. This example uses the hub-and-spoke topology shown in the figure above. Creating the VRFsvrf definition Down rd 100:1 address-family ipv4 route-target export 100:0 exit-address-family ! vrf definition Up rd 100:2 address-family ipv4 route-target import 100:1 exit-address-family Configuring BGP Toward Corerouter bgp 100 no bgp default ipv4-unicast bgp log-neighbor-changes bgp graceful-restart restart-time 120 bgp graceful-restart stalepath-time 360 bgp graceful-restart neighbor 10.13.13.13 remote-as 100 neighbor 10.13.13.13 update-source Loopback0 ! address-family vpnv4 neighbor 10.13.13.13 activate neighbor 10.13.13.13 send-community extended bgp scan-time import 5 exit-address-family Configuring BGP Toward Edgeaddress-family ipv4 vrf Up no auto-summary no synchronization exit-address-family ! address-family ipv4 vrf Down redistribute ospf 1000 vrf Down no auto-summary no synchronization exit-address-family Spoke PE's Core-Facing Interfaces and Processesinterface Loopback 0 ip address 10.11.11.11 255.255.255.255 ! interface POS 3/0/2 ip address 10.0.1.1 255.0.0.0 mpls label protocol ldp mpls ip ! router ospf 100 log-adjacency-changes auto-cost reference-bandwidth 1000 nsf enforce global redistribute connected subnets network 10.11.11.11 0.0.0.0 area 100 network 10.0.1.0 0.255.255.255 area 100 Spoke PE's Edge-Facing Interfaces and Processesinterface Loopback 100 vrf forwarding Down ip address 10.22.22.22 255.255.255.255 ! interface POS 3/0/1 vrf forwarding Up downstream Down ip address 10.0.0.1 255.0.0.0 ! interface POS 3/0/3 vrf forwarding Up downstream Down ip address 10.2.0.1 255.0.0.0 ! router ospf 1000 vrf Down router-id 10.22.22.22 log-adjacency-changes auto-cost reference-bandwidth 1000 nsf enforce global redistribute connected subnets redistribute bgp 100 metric-type 1 subnets network 10.22.22.22 0.0.0.0 area 300 network 10.0.0.0 0.255.255.255 area 300 network 10.2.0.0 0.255.255.255 area 300 default-information originate Additional ReferencesRelated DocumentsMIBsTechnical Assistance
Feature Information for MPLS VPN Half-Duplex VRFThe 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.
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R) Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental. © 2012 Cisco Systems, Inc. All rights reserved.
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