Implementing MPLS Layer 3 VPNs

A Multiprotocol Label Switching (MPLS) Layer 3 Virtual Private Network (VPN) consists of a set of sites that are interconnected by means of an MPLS provider core network. At each customer site, one or more customer edge (CE) routers attach to one or more provider edge (PE) routers.

This module provides the conceptual and configuration information for MPLS Layer 3 VPNs on Cisco NCS 5000 Series Routers.


Note
You must acquire an evaluation or permanent license in order to use MPLS Layer 3 VPN functionality. For more information about licenses, see the module in the System Management Configuration Guide for Cisco NCS 5000 Series Routers.

For a complete description of the commands listed in this module, refer these command references:

This chapter includes topics on:

MPLS L3VPN Overview

Before defining an MPLS VPN, VPN in general must be defined. A VPN is:

  • An IP-based network delivering private network services over a public infrastructure

  • A set of sites that are allowed to communicate with each other privately over the Internet or other public or private networks

Conventional VPNs are created by configuring a full mesh of tunnels or permanent virtual circuits (PVCs) to all sites in a VPN. This type of VPN is not easy to maintain or expand, as adding a new site requires changing each edge device in the VPN.

MPLS-based VPNs are created in Layer 3 and are based on the peer model. The peer model enables the service provider and the customer to exchange Layer 3 routing information. The service provider relays the data between the customer sites without customer involvement.

MPLS VPNs are easier to manage and expand than conventional VPNs. When a new site is added to an MPLS VPN, only the edge router of the service provider that provides services to the customer site needs to be updated.

The following figure depicts a basic MPLS VPN topology.

Figure 1. Basic MPLS VPN Topology


These are the basic components of MPLS VPN:

  • Provider (P) router—Router in the core of the provider network. P routers run MPLS switching and do not attach VPN labels to routed packets. VPN labels are used to direct data packets to the correct private network or customer edge router.

  • PE router—Router that attaches the VPN label to incoming packets based on the interface or sub-interface on which they are received, and also attaches the MPLS core labels. A PE router attaches directly to a CE router.

  • Customer (C) router—Router in the Internet service provider (ISP) or enterprise network.

  • Customer edge (CE) router—Edge router on the network of the ISP that connects to the PE router on the network. A CE router must interface with a PE router.

How MPLS L3VPN Works

MPLS VPN functionality is enabled at the edge of an MPLS network. The PE router performs the following tasks:

  • Exchanges routing updates with the CE router

  • Translates the CE routing information into VPN version 4 (VPNv4) routes

  • Exchanges VPNv4 routes with other PE routers through the Multiprotocol Border Gateway Protocol (MP-BGP)

Major Components of MPLS L3VPN

An MPLS-based VPN network has three major components:

  • VPN route target communities—A VPN route target community is a list of all members of a VPN community. VPN route targets need to be configured for each VPN community member.

  • Multiprotocol BGP (MP-BGP) peering of the VPN community PE routers—MP-BGP propagates VRF reachability information to all members of a VPN community. MP-BGP peering needs to be configured in all PE routers within a VPN community.

  • MPLS forwarding—MPLS transports all traffic between all VPN community members across a VPN service-provider network.

A one-to-one relationship does not necessarily exist between customer sites and VPNs. A given site can be a member of multiple VPNs. However, a site can associate with only one VRF. A customer-site VRF contains all the routes available to the site from the VPNs of which it is a member.

Read more at Major Components of MPLS L3VPN—Details.

Restrictions for MPLS L3VPN

Implementing MPLS L3VPN in Cisco NCS 5000 Series Routers is subjected to these restrictions:

  • Fragmentation of MPLS packets that exceed egress MTU is not supported. Fragmentation is not supported for IP->MPLS imposition as well. Hence, it is recommended to use Maximum MTU (9216) value on all interfaces in the MPLS core.

  • L3VPN prefix lookup always yields a single path. In case of multiple paths at IGP or BGP level, path selection at each level is done using the prefix hash in control plane. The selected path is programmed in the data plane.

  • TTL propagation cannot be disabled. TTL propagation always happens from IP->MPLS and MPLS->IP.

Apart from the specific ones mentioned above, these generic restrictions for implementing MPLS L3VPNs also apply for Cisco NCS 5000 Series Routers:

  • Multihop VPN-IPv4 eBGP is not supported for configuring eBGP routing between autonomous systems or subautonomous systems in an MPLS VPN.

  • MPLS VPN supports only IPv4 address families.

The following restrictions apply when configuring MPLS VPN Inter-AS with ASBRs exchanging IPv4 routes and MPLS labels:

  • For networks configured with eBGP multihop, a label switched path (LSP) must be configured between non adjacent routers.

  • Inter-AS supports IPv4 routes only. IPv6 is not supported.


Note
The physical interfaces that connect the BGP speakers must support FIB and MPLS.

How to Implement MPLS Layer 3 VPNs

Implementing MPLS L3VPNs involves these main tasks:

Prerequisites for Implementing MPLS L3VPN

These are the prerequisites to configure MPLS L3VPN:

  • You must be in a user group associated with a task group that includes the proper task IDs for these commands:

      • BGP

      • IGP

      • MPLS

      • MPLS Layer 3 VPN

  • If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
  • To configure MPLS Layer 3 VPNs, routers must support MPLS forwarding and Forwarding Information Base (FIB).

Configure the Core Network

Consider a network topology where MPLS L3VPN services are transported over MPLS LDP core.

Figure 2. L3VPN over MPLS LDP


Configuring the core network involves these main tasks:

Assess the Needs of MPLS VPN Customers

Before configuring an MPLS VPN, the core network topology must be identified so that it can best serve MPLS VPN customers. The tasks listed below helps to identify the core network topology.

  • Identify the size of the network:

    Identify the following to determine the number of routers and ports required:

    • How many customers to be supported?
    • How many VPNs are required for each customer?
    • How many virtual routing and forwarding (VRF) instances are there for each VPN?

  • Determine the routing protocols required in the core.

  • Determine if BGP load sharing and redundant paths in the MPLS VPN core are required.

Configure Routing Protocols in the Core

You can use RIP, OSPF or IS-IS as the routing protocol in the core.

Configuration Example

This example lists the steps to configure OSPF as the routing protocol in the core. 


Router-PE1#configure
Router-PE1(config)#router ospf dc-core
Router-PE1(config-ospf)#address-family ipv4 unicast
Router-PE1(config-ospf)#area 1
Router-PE1(config-ospf-ar)#interface HundredGigE0/0/0/2
Router-PE1(config-ospf-ar)#
Router-PE1(config-ospf-vrf-ar-if)#commit
Running Configuration 

router ospf dc-core
 router-id 13.13.13.1
 address-family ipv4 unicast
 area 1
  interface HundredGigE0/0/0/2
  
  
  !
 !
!
Verification

  • Verify the OSPF neighbor and ensure that the State is displayed as 'FULL'. 

    
Router-PE1# show ospf neighbor
Neighbors for OSPF dc-core

Neighbor ID     Pri   State           Dead Time   Address         Interface
16.16.16.1      1     FULL/DR  00:00:34    191.22.1.2      HundredGigE0/0/0/2
    Neighbor is up for 1d18h

Total neighbor count: 1
Related Topics

For more details on configuring the routing protocol, see Routing Configuration Guide for Cisco NCS 5000 Series Routers and BGP Configuration Guide for Cisco NCS 5000 Series Routers.

Associated Commands

Configure MPLS in the Core

To enable MPLS on all routers in the core, you must configure a Label Distribution Protocol (LDP).

You can also transport MPLS L3VPN services using segment routing in the core. For details, see Configure Segment Routing in MPLS Core.

Configuration Example

This example lists the steps to configure LDP in MPLS core. 


Router-PE1#configure
Router-PE1(config)#mpls ldp
Router-PE1(config-ldp)#router-id 13.13.13.1
Router-PE1(config-ldp)#address-family ipv4
Router-PE1(config-ldp-af)#exit
Router-PE1(config-ldp)#interface HundredGigE0/0/0/2
Router-PE1(config-ldp)#
Router-PE1(config-ldp)#
Router-PE1(config-ldp)#commit

Repeat this configuration in PE2 and P routers as well.

Running Configuration 

mpls ldp
 router-id 13.13.13.1
 address-family ipv4
 !
 interface HundredGigE0/0/0/2
 
 
 !
!
Verification

  • Verify that the neighbor (16.16.16.1) is UP through the core interface: 

    
Router-PE1#show mpls ldp neighbor
Peer LDP Identifier: 16.16.16.1:0
  TCP connection: 16.16.16.1:47619 - 13.13.13.1:646
  Graceful Restart: No
  Session Holdtime: 180 sec
  State: Oper; Msgs sent/rcvd: 40395/35976; Downstream-Unsolicited
  Up time: 2w2d
  LDP Discovery Sources:
    IPv4: (1)
      HundredGigE0/0/0/2
    IPv6: (0)
  Addresses bound to this peer:
    IPv4: (6)
      10.64.98.32    87.0.0.2       88.88.88.14    50.50.50.50     
      178.0.0.1      192.1.1.1      
    IPv6: (0)
Related Topics

For more details on configuring MPLS LDP, see the Implementing MPLS Label Distribution Protocol chapter in the MPLS Configuration Guide for Cisco NCS 5000 Series Routers.

Associated Commands

Determine if FIB is Enabled in the Core

Forwarding Information Base (FIB) must be enabled on all routers in the core, including the provider edge (PE) routers. For information on how to determine if FIB is enabled, see the Implementing Cisco Express Forwarding module in the IP Addresses and Services Configuration Guide for Cisco NCS 5000 Series Routers.

Configure Multiprotocol BGP on the PE Routers and Route Reflectors

Multiprotocol BGP (MP-BGP) propagates VRF reachability information to all members of a VPN community. You must configure MP-BGP peering in all the PE routers within a VPN community.

Figure 3. Multiprotocol BGP on PE Routers


Configuration Example

This example shows how to configure MP-BGP on PE1. The loopback address (20.20.20.1) of PE2 is specified as the neighbor of PE1. Similarly, you must perform this configuration on PE2 node as well, with the loopback address (13.13.13.1) of PE1 specified as the neighbor of PE2. 


Router-PE1#configure
Router-PE1(config)#router bgp 2001
Router-PE1(config-bgp)#bgp router-id 13.13.13.1
Router-PE1(config-bgp)#address-family ipv4 unicast
Router-PE1(config-bgp-af)#exit
Router-PE1(config-bgp)#address-family vpnv4 unicast
Router-PE1(config-bgp-af)#exit
Router-PE1(config-bgp)#neighbor 20.20.20.1
Router-PE1(config-bgp-nbr)#remote-as 2001
Router-PE1(config-bgp-nbr)#update-source loopback 0
Router-PE1(config-bgp-nbr)#address-family ipv4 unicast
Router-PE1(config-bgp-nbr-af)#exit
Router-PE1(config-bgp-nbr)#address-family vpnv4 unicast
Router-PE1(config-bgp-nbr-af)#exit
Router-PE1(config-bgp-nbr)#exit
/* VRF configuration */
Router(config-bgp)# vrf vrf1601
Router-PE1(config-bgp-vrf)#rd 2001:1601
Router-PE1(config-bgp-vrf)#address-family ipv4 unicast
Router-PE1(config-bgp-vrf-af)#label mode per-vrf
Router-PE1(config-bgp-vrf-af)#redistribute connected
Router-PE1(config-bgp-vrf-af)#commit
Running Configuration 

router bgp 2001
 bgp router-id 13.13.13.1
 address-family ipv4 unicast
 !
 address-family vpnv4 unicast
 !
 neighbor 20.20.20.1
  remote-as 2001
  update-source Loopback0
  address-family vpnv4 unicast
  !
  address-family ipv4 unicast
  !
 !
 vrf vrf1601
  rd 2001:1601
  address-family ipv4 unicast
   label mode per-vrf
   redistribute connected
  !
 !
Verification

  • Verify if the BGP state is established, and if the Remote AS and local AS displays the same value (2001 in this example): 

    
Router-PE1#show bgp neighbor

BGP neighbor is 20.20.20.1
 Remote AS 2001, local AS 2001, internal link
 Remote router ID 20.20.20.1
  BGP state = Established, up for 1d19h
  NSR State: None
  Last read 00:00:04, Last read before reset 00:00:00
  Hold time is 60, keepalive interval is 20 seconds
  Configured hold time: 60, keepalive: 30, min acceptable hold time: 3
  Last write 00:00:16, attempted 19, written 19
  Second last write 00:00:36, attempted 19, written 19
  Last write before reset 00:00:00, attempted 0, written 0
  Second last write before reset 00:00:00, attempted 0, written 0
  Last write pulse rcvd  Apr 12 10:31:20.739 last full not set pulse count 27939
  Last write pulse rcvd before reset 00:00:00
  Socket not armed for io, armed for read, armed for write
  Last write thread event before reset 00:00:00, second last 00:00:00
  Last KA expiry before reset 00:00:00, second last 00:00:00
  Last KA error before reset 00:00:00, KA not sent 00:00:00
  Last KA start before reset 00:00:00, second last 00:00:00
  Precedence: internet
  Non-stop routing is enabled
  Multi-protocol capability received
  Neighbor capabilities:
    Route refresh: advertised (old + new) and received (old + new)
    Graceful Restart (GR Awareness): received
    4-byte AS: advertised and received
    Address family IPv4 Unicast: advertised and received
    Address family VPNv4 Unicast: advertised and received
  Received 25595 messages, 0 notifications, 0 in queue
  Sent 8247 messages, 0 notifications, 0 in queue
  Minimum time between advertisement runs is 0 secs
  Inbound message logging enabled, 3 messages buffered
  Outbound message logging enabled, 3 messages buffered

 For Address Family: IPv4 Unicast
  BGP neighbor version 484413
  Update group: 0.4 Filter-group: 0.3  No Refresh request being processed
  Inbound soft reconfiguration allowed
  NEXT_HOP is always this router
  AF-dependent capabilities:
    Outbound Route Filter (ORF) type (128) Prefix:
      Send-mode: advertised, received
      Receive-mode: advertised, received
    Graceful Restart capability received
      Remote Restart time is 120 seconds
      Neighbor did not preserve the forwarding state during latest restart
    Additional-paths Send: advertised and received
    Additional-paths Receive: advertised and received
  Route refresh request: received 1, sent 1
  Policy for incoming advertisements is pass-all
  Policy for outgoing advertisements is pass-all
  24260 accepted prefixes, 24260 are bestpaths
  Cumulative no. of prefixes denied: 0. 
  Prefix advertised 2000, suppressed 0, withdrawn 0
  Maximum prefixes allowed 1048576
  Threshold for warning message 75%, restart interval 0 min
  AIGP is enabled
  An EoR was received during read-only mode
  Last ack version 484413, Last synced ack version 0
  Outstanding version objects: current 0, max 1
  Additional-paths operation: Send and Receive
  Send Multicast Attributes
  Advertise VPNv4 routes enabled with defaultReoriginate,disable Local with stitching-RT option

 For Address Family: VPNv4 Unicast
  BGP neighbor version 798487
  Update group: 0.2 Filter-group: 0.1  No Refresh request being processed
  AF-dependent capabilities:
    Graceful Restart capability received
      Remote Restart time is 120 seconds
      Neighbor did not preserve the forwarding state during latest restart
    Additional-paths Send: advertised and received
    Additional-paths Receive: advertised and received
  Route refresh request: received 0, sent 0
  29150 accepted prefixes, 29150 are bestpaths
  Cumulative no. of prefixes denied: 0. 
  Prefix advertised 7200, suppressed 0, withdrawn 0
  Maximum prefixes allowed 2097152
  Threshold for warning message 75%, restart interval 0 min
  AIGP is enabled
  An EoR was received during read-only mode
  Last ack version 798487, Last synced ack version 0
  Outstanding version objects: current 0, max 1
  Additional-paths operation: Send and Receive
  Send Multicast Attributes
  Advertise VPNv4 routes enabled with defaultReoriginate,disable Local with stitching-RT option

  Connections established 1; dropped 0
  Local host: 13.13.13.1, Local port: 35018, IF Handle: 0x00000000
  Foreign host: 20.20.20.1, Foreign port: 179
  Last reset 00:00:00

  • Verify if all the IP addresses are learnt on PE1 from PE2: 

    
Router-PE1#show bgp vpnv4 unicast

BGP router identifier 13.13.13.1, local AS number 2001
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0   RD version: 0
BGP main routing table version 798487
BGP NSR Initial initsync version 15151 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs

Status codes: s suppressed, d damped, h history, * valid, > best
              i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
   Network            Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 2001:1601 (default for vrf vrf1601)
*> 20.13.1.1/32       192.13.26.5                            0 7501 i
*> 20.13.1.2/32       192.13.26.5                            0 7501 i
*> 20.13.1.3/32       192.13.26.5                            0 7501 i
*> 20.13.1.4/32       192.13.26.5                            0 7501 i
*> 20.13.1.5/32       192.13.26.5                            0 7501 i
*>i20.14.1.1/3214.14.14.1                    100      0 8501 i
*>i20.14.1.2/3214.14.14.1                    100      0 8501 i
*>i20.14.1.3/3214.14.14.1                    100      0 8501 i
*>i20.14.1.4/3214.14.14.1                    100      0 8501 i
*>i20.14.1.5/3214.14.14.1                    100      0 8501 i
Related Topics

For more details on Multiprotocol BGP, see BGP Configuration Guide for Cisco NCS 5000 Series Routers.

Associated Commands
Associated Commands

Connect MPLS VPN Customers

Connecting MPLS VPN customers involves these main tasks:

Define VRFs on PE Routers to Enable Customer Connectivity

VPN routing and forwarding (VRF) defines the VPN membership of a customer site attached to a PE router. A one-to-one relationship does not necessarily exist between customer sites and VPNs. A site can be a member of multiple VPNs. However, a site can associate with only one VRF. A VRF contains all the routes available to the site from the VPNs of which it is a member. The distribution of VPN routing information is controlled through the use of VPN route target communities, implemented by BGP extended communities.

Configuration Example

This example configures a VRF instance (vrf1601) and specifies the import and export route-targets(2001:1601). The import route policy is the one that can be imported into the local VPN. The export route policy is the one that can be exported from the local VPN. The import route-target configuration allows exported VPN routes to be imported into the VPN if one of the route targets of the exported route matches one of the local VPN import route targets. When the route is advertised to other PE routers, the export route target is sent along with the route as an extended community. 


Router-PE1#configure
Router-PE1(config)#vrf vrf1601
Router-PE1(config-vrf)#address-family ipv4 unicast
Router-PE1(config-vrf-af)#import route-target
Router-PE1(config-vrf-af-import-rt)#2001:1601
Router-PE1(config-vrf-af-import-rt)#exit
Router-PE1(config-vrf-af)#export route-target
Router-PE1(config-vrf-af-export-rt)#2001:1601
Router-PE1(config-vrf-af-export-rt)#commit

This VRF instance is then associated with the respective BGP instance.

Running Configuration 

vrf vrf1601
 address-family ipv4 unicast
  import route-target
   2001:1601
  !
  export route-target
   2001:1601
  !
 !
!
Verification

Verify the import and export route targets. 


Router-PE1#show vrf vrf1601
VRF                  RD          RT                 AFI   SAFI     
vrf1601              2001:1601          
                                 import  2001:1601   IPV4  Unicast  
                                 export  2001:1601   IPV4  Unicast
Related Topics
Associated Commands

Configure VRF Interfaces on PE Routers for Each VPN Customer

After a VRF instance is created, you must associate that VRF instance with an interface or a sub-interface on the PE routers.


Note
You must remove the IPv4 or IPv6 addresses from an interface prior to assigning, removing, or changing an interface's VRF. If this is not done in advance, any attempt to change the VRF on an IP interface is rejected.
Configuration Example

This example assigns an IP address 192.13.26.6 to the interface (HundredGigE0/0/0/14.1601 ) on PE1 router and associates the VRF instance vrf1601 , to that interface. 


Router-PE1#configure
Router-PE1(config)#interface HundredGigE0/0/0/14.1601
Router-PE1(config-if)#vrf vrf1601
Router-PE1(config-if)#ipv4 address 192.13.26.6 255.255.255.252
Router-PE1(config-if)#encapsulation dot1q 1601
Router-PE1(config)#commit
Running Configuration 

interface HundredGigE0/0/0/14.1601
 vrf vrf1601
 ipv4 address 192.13.26.6 255.255.255.252
 encapsulation dot1q 1601
!
Verification

  • Verify that the interface with which the VRF is associated, is UP. 

    
Router-PE1#show ipv4 vrf vrf1601 interface 
interface HundredGigE0/0/0/14.1601 is Up, ipv4 protocol is Up
  Vrf is vrf1601 (vrfid 0x60000001)
  Internet address is 192.13.26.6/30
  MTU is 1518 (1500 is available to IP)
  Helper address is not set
  Multicast reserved groups joined: 224.0.0.2 224.0.0.1
  Directed broadcast forwarding is disabled
  Outgoing access list is not set
  Inbound  common access list is not set, access list is not set
  Proxy ARP is disabled
  ICMP redirects are never sent
  ICMP unreachables are always sent
  ICMP mask replies are never sent
  Table Id is 0xe0000001
Related Topics

Configure Routing Protocol Between the PE and CE Routers

Configure BGP as the Routing Protocol Between the PE and CE Routers

BGP distributes reachability information for VPN-IPv4 prefixes for each VPN. PE to PE or PE to route reflector (RR) sessions are iBGP sessions, and PE to CE sessions are eBGP sessions. PE to CE eBGP sessions can be directly or indirectly connected (eBGP multihop).

Figure 4. BGP as the Routing Protocol between PE and CE Routers


Configuration Example

This example lists the steps to configure BGP as the routing protocol between the PE and CE routers. The route policy, pass-all in this example, must be configured before it can be attached.

PE1: 


Router-PE1#configure
Router-PE1(config)#router bgp 2001
Router-PE1(config-bgp)#bgp router-id 13.13.13.1
Router-PE1(config-bgp)#address-family ipv4 unicast
Router-PE1(config-bgp-af)#exit
Router-PE1(config-bgp)#address-family vpnv4 unicast
Router-PE1(config-bgp-af)#exit
/* VRF configuration */
Router-PE1(config-bgp)#vrf vrf1601
Router-PE1(config-bgp-vrf)#rd 2001:1601
Router-PE1(config-bgp-vrf)#address-family ipv4 unicast
Router-PE1(config-bgp-vrf-af)#label mode per-vrf
Router-PE1(config-bgp-vrf-af)#redistribute connected
Router-PE1(config-bgp-vrf-af)#exit
Router-PE1(config-bgp-vrf)#neighbor 192.13.26.5
Router-PE1(config-bgp-vrf-nbr)#remote-as 7501
Router-PE1(config-bgp-vrf-nbr)#address-family ipv4 unicast
Router-PE1(config-bgp-vrf-nbr-af)#route-policy pass-all in
Router-PE1(config-bgp-vrf-nbr-af)#route-policy pass-all out
Router-PE1(config-bgp-vrf-nbr-af)#commit

CE1: 


Router-CE1#configure
Router-CE1(config)#router bgp 2001
Router-CE1(config-bgp)#bgp router-id 8.8.8.1
Router-CE1(config-bgp)#address-family ipv4 unicast
Router-CE1(config-bgp-af)#exit
Router-CE1(config-bgp)#address-family vpnv4 unicast
Router-CE1(config-bgp-af)#exit
Router-CE1(config-bgp)#neighbor 192.13.26.6
Router-CE1(config-bgp-nbr)#remote-as 2001
Router-CE1(config-bgp-nbr)#address-family ipv4 unicast
Router-CE1(config-bgp-nbr-af)#route-policy pass-all in
Router-CE1(config-bgp-nbr-af)#route-policy pass-all out
Router-CE1(config-bgp-nbr-af)#commit
Running Configuration

PE1: 


router bgp 2001
 bgp router-id 13.13.13.1
 address-family ipv4 unicast
 !
 address-family vpnv4 unicast
 !
 vrf vrf1601
  rd 2001:1601
  address-family ipv4 unicast
   label mode per-vrf
   redistribute connected
  !
  neighbor 192.13.26.5
   remote-as 7501
   address-family ipv4 unicast
    route-policy pass-all in
    route-policy pass-all out
   !
  !
 !

CE1: 


router bgp 7501
 bgp router-id 8.8.8.1
 address-family ipv4 unicast
 !
 address-family vpnv4 unicast
 !
 neighbor 192.13.26.6
  remote-as 2001
  address-family ipv4 unicast
   route-policy pass-all in
   route-policy pass-all out
 !
!
Verification

  • PE1: 

    
Router-PE1#show bgp neighbor
BGP neighbor is 192.13.26.5
 Remote AS 6553700, local AS 2001, external link
 Administratively shut down
 Remote router ID 192.13.26.5
  BGP state = Established 
  NSR State: None
  Last read 00:00:04, Last read before reset 00:00:00
  Hold time is 60, keepalive interval is 20 seconds
  Configured hold time: 60, keepalive: 30, min acceptable hold time: 3
  Last write 00:00:16, attempted 19, written 19
  Second last write 00:00:36, attempted 19, written 19
  Last write before reset 00:00:00, attempted 0, written 0
  Second last write before reset 00:00:00, attempted 0, written 0
  Last write pulse rcvd  Apr 12 10:31:20.739 last full not set pulse count 27939
  Last write pulse rcvd before reset 00:00:00
  Socket not armed for io, armed for read, armed for write
  Last write thread event before reset 00:00:00, second last 00:00:00
  Last KA expiry before reset 00:00:00, second last 00:00:00
  Last KA error before reset 00:00:00, KA not sent 00:00:00
  Last KA start before reset 00:00:00, second last 00:00:00
  Precedence: internet
  Non-stop routing is enabled
  Graceful restart is enabled
  Restart time is 120 seconds
  Stale path timeout time is 360 seconds
  Enforcing first AS is enabled
  Multi-protocol capability not received
  Received 0 messages, 0 notifications, 0 in queue
  Sent 0 messages, 0 notifications, 0 in queue
  Minimum time between advertisement runs is 30 secs
  Inbound message logging enabled, 3 messages buffered
  Outbound message logging enabled, 3 messages buffered

 For Address Family: IPv4 Unicast
  BGP neighbor version 0
  Update group: 0.2 Filter-group: 0.0  No Refresh request being processed
  Inbound soft reconfiguration allowed
  AF-dependent capabilities:
    Outbound Route Filter (ORF) type (128) Prefix:
      Send-mode: advertised
      Receive-mode: advertised
    Graceful Restart capability advertised
      Local restart time is 120, RIB purge time is 600 seconds
      Maximum stalepath time is 360 seconds
  Route refresh request: received 0, sent 0
  Policy for incoming advertisements is pass-all
  Policy for outgoing advertisements is pass-all
  0 accepted prefixes, 0 are bestpaths
  Cumulative no. of prefixes denied: 0. 
  Prefix advertised 0, suppressed 0, withdrawn 0
  Maximum prefixes allowed 1048576
  Threshold for warning message 75%, restart interval 0 min
  An EoR was not received during read-only mode
  Last ack version 1, Last synced ack version 0
  Outstanding version objects: current 0, max 0
  Additional-paths operation: None
  Advertise VPNv4 routes enabled with defaultReoriginate,disable Local with stitching-RT option
  Advertise VPNv6 routes is enabled with default option


  Connections established 1; dropped 0
  Local host: 192.13.26.6, Local port: 23456, IF Handle: 0x00000000
  Foreign host: 192.13.26.5, Foreign port: 179
  Last reset 03:12:58, due to Admin. shutdown (CEASE notification sent - administrative shutdown)
  Time since last notification sent to neighbor: 03:12:58
  Notification data sent:
    None
  External BGP neighbor not directly connected.

  • CE1: 

    
Router-CE1#show bgp neighbor
BGP neighbor is 192.13.26.6
 Remote AS 2001, local AS 6553700, external link
 Remote router ID 192.13.26.6
  BGP state = Established 
  NSR State: None
  Last read 00:00:04, Last read before reset 00:00:00
  Hold time is 60, keepalive interval is 20 seconds
  Configured hold time: 60, keepalive: 30, min acceptable hold time: 3
  Last write 00:00:16, attempted 19, written 19
  Second last write 00:00:36, attempted 19, written 19
  Last write before reset 00:00:00, attempted 0, written 0
  Second last write before reset 00:00:00, attempted 0, written 0
  Last write pulse rcvd  Apr 12 10:31:20.739 last full not set pulse count 27939
  Last write pulse rcvd before reset 00:00:00
  Socket not armed for io, armed for read, armed for write
  Last write thread event before reset 00:00:00, second last 00:00:00
  Last KA expiry before reset 00:00:00, second last 00:00:00
  Last KA error before reset 00:00:00, KA not sent 00:00:00
  Last KA start before reset 00:00:00, second last 00:00:00
  Precedence: internet
  Non-stop routing is enabled
  Graceful restart is enabled
  Restart time is 120 seconds
  Stale path timeout time is 360 seconds
  Enforcing first AS is enabled
  Multi-protocol capability not received
  Received 0 messages, 0 notifications, 0 in queue
  Sent 0 messages, 0 notifications, 0 in queue
  Minimum time between advertisement runs is 30 secs
  Inbound message logging enabled, 3 messages buffered
  Outbound message logging enabled, 3 messages buffered

 For Address Family: IPv4 Unicast
  BGP neighbor version 0
  Update group: 0.1 Filter-group: 0.0  No Refresh request being processed
  Inbound soft reconfiguration allowed
  AF-dependent capabilities:
    Outbound Route Filter (ORF) type (128) Prefix:
      Send-mode: advertised
      Receive-mode: advertised
    Graceful Restart capability advertised
      Local restart time is 120, RIB purge time is 600 seconds
      Maximum stalepath time is 360 seconds
  Route refresh request: received 0, sent 0
  Policy for incoming advertisements is pass-all
  Policy for outgoing advertisements is pass-all
  0 accepted prefixes, 0 are bestpaths
  Cumulative no. of prefixes denied: 0. 
  Prefix advertised 0, suppressed 0, withdrawn 0
  Maximum prefixes allowed 1048576
  Threshold for warning message 75%, restart interval 0 min
  An EoR was not received during read-only mode
  Last ack version 1, Last synced ack version 0
  Outstanding version objects: current 0, max 0
  Additional-paths operation: None

  Connections established 0; dropped 0
  Local host: 192.13.26.5, Local port: 179, IF Handle: 0x00000000
  Foreign host: 192.13.26.6, Foreign port: 23456
  Last reset 00:00:00
  External BGP neighbor not directly connected.
Related Topics

For more details on BGP, see BGP Configuration Guide for Cisco NCS 5000 Series Routers.

Associated Commands

Configure RIPv2 as the Routing Protocol Between the PE and CE Routers

Figure 5. RIP as the Routing Protocol between PE and CE Routers


Configuration Example

This example lists the steps to configure RIPv2 as the routing protocol between the PE and CE routers. The VRF instance vrf1601 is configured in the router rip configuration mode and the respective interface (TenGigE0/0/0/14.1601 on PE1 and TenGigE0/0/0/18.1601 on CE1) is associated with that VRF. The redistribute option specifies routes to be redistributed into RIP.

PE1: 

Router-PE1#configure
Router-PE1(config)#router rip
Router-PE1(config-rip)#vrf vrf1601
Router-PE1(config-rip-vrf)#interface TenGigE0/0/0/14.1601
Router-PE1(config-bgp-vrf-if)#exit
Router-PE1(config-bgp-vrf)#redistribute bgp 2001
Router-PE1(config-bgp-vrf)#redistribute connected
Router-PE1(config-bgp-vrf)#commit
CE1: 

Router-CE1#configure
Router-CE1(config)#router rip
Router-CE1(config-rip)#vrf vrf1601
Router-CE1(config-rip-vrf)#interface TenGigE0/0/0/14.1601
Router-CE1(config-bgp-vrf-if)#exit
Router-CE1(config-bgp-vrf)#redistribute connected
Router-CE1(config-bgp-vrf)#commit
Running Configuration
PE1: 

Router-PE1#show running-config router rip
router rip
 vrf vrf1601
  interface TenGigE0/0/0/14.1601
  !
  redistribute bgp 2001
  redistribute connected
 !
!
CE1: 

Router-CE1#show running-config router rip
router rip
 vrf vrf1601
  interface TenGigE0/0/0/18.1601
  !
  redistribute connected
 !
!
Related Topics
Associated Commands

Configure Static Routes Between the PE and CE Routers

Configuration Example

In this example, the static route is assigned to VRF, vrf1601. 


Router-PE1#configure
Router-PE1(config)#router static
Router-PE1(config-static)#vrf vrf1601
Router-PE1(config-static-vrf)#address-family ipv4 unicast
Router-PE1(config-static-vrf-afi)#23.13.1.1/32 TenGigE0/0/0/14.1601 192.13.3.93
Router-PE1(config-static-vrf-afi)#commit

Repeat the configuration in CE1, with the respective interface values.

Running Configuration

PE1: 


router static
 vrf vrf1601
  address-family ipv4 unicast
   23.13.1.1/32 TenGigE0/0/0/14.1601 192.13.3.93
  !
 !
!

CE1: 


router static
 vrf vrf1601
  address-family ipv4 unicast
   23.8.1.2/32 TenGigE0/0/0/18.1601 192.8.3.94
  !
 !
!
Related Topics
Associated Commands

  • router static

Configure OSPF as the Routing Protocol Between the PE and CE Routers

You can use RIP, OSPF or ISIS as the routing protocol between the PE and CE routers.

Figure 6. OSPF as the Routing Protocol between PE and CE Routers


Configuration Example

This example lists the steps to configure PE-CE routing sessions that use OSPF routing protocol. A VRF instance vrf1601 is configured in the router ospf configuration mode. The router-id for the OSPF process is 13.13.13.1. The redistribute option specifies routes to be redistributed into OSPF. The OSPF area is configured to be 1 and interface TenGigE0/0/0/14.1601 is associated with that area to enable routing on it.

PE1: 


Router-PE1#configure
Router-PE1(config)#router ospf pe-ce-ospf-vrf
Router-PE1(config-ospf)#router-id 13.13.13.1
Router-PE1(config-ospf)#vrf vrf1601
Router-PE1(config-ospf-vrf)#redistribute connected
Router-PE1(config-ospf-vrf)#redistribute bgp 2001
Router-PE1(config-ospf-vrf)#area 1
Router-PE1(config-ospf-vrf-ar)#interface TenGigE0/0/0/14.1601
Router-PE1(config-ospf-vrf-ar)# commit

Repeat this configuration at PE2 node as well.

CE1: 


Router-CE1#configure
Router-CE1(config)#router ospf ospf pe-ce-1
Router-CE1(config-ospf)#router-id 8.8.8.1
Router-CE1(config-ospf)#vrf vrf1601
Router-CE1(config-ospf-vrf)#area 1
Router-CE1(config-ospf-vrf-ar)#interface TenGigE0/0/0/18.1601
Router-CE1(config-ospf-vrf-ar)#commit
Running Configuration

PE1: 


router ospf pe-ce-ospf-vrf
 router-id 13.13.13.1
 vrf vrf1601
  redistribute connected
  redistribute bgp 2001
  area 1
   interface TenGigE0/0/0/14.1601
   !
  !
 !
!

CE1: 


router ospf pe-ce-1
 router-id 8.8.8.1
 vrf vrf1601
  area 1
   interface TenGigE0/0/0/18.1601
   !
  !
 !
!
Related Topics
Associated Commands

Verify MPLS L3VPN Configuration

You must verify these to ensure the successful configuration of MPLS L3VPN:

Verify the L3VPN Traffic Flow

  • Verify the number of bytes switched for the label associated with the VRF (vrf1601):

    P node: 

    
Router-P#show mpls forwarding
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ------------
24119  Pop         20.20.20.1/32      Hu0/0/0/0    191.31.1.90     2170204180148

    PE2: 

    
Router#show mpls forwarding
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched   
------ ----------- ------------------ ------------ --------------- ------------ 
24031  Aggregate   vrf1601: Per-VRF Aggr[V]   \
                                      vrf1601                      11124125835

Verify the Underlay (transport)

  • Verify if the LDP neighbor connection is established with the respective neighbor: 

    
Router-PE1#show mpls ldp neighbor
Peer LDP Identifier: 16.16.16.1:0
  TCP connection: 16.16.16.1:47619 - 13.13.13.1:646
  Graceful Restart: No
  Session Holdtime: 180 sec
  State: Oper; Msgs sent/rcvd: 40395/35976; Downstream-Unsolicited
  Up time: 2w2d
  LDP Discovery Sources:
    IPv4: (1)
      TenGigE0/0/0/2
    IPv6: (0)
  Addresses bound to this peer:
    IPv4: (6)
      10.64.98.32    87.0.0.2       88.88.88.14    50.50.50.50     
      178.0.0.1      192.1.1.1      
    IPv6: (0)

  • Verify if the label update is received by the FIB: 

    

Router-PE1#show mpls forwarding
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ------------    
24036  Pop         16.16.16.1/32      Hu0/0/0/2    191.22.1.2      293294               
24037  24165       18.18.18.1/32      Hu0/0/0/2    191.22.1.2      500                   
24039  24167       20.20.20.1/32      Hu0/0/0/2    191.22.1.2      17872433
	      24167	      20.20.20.1/32	     Hu0/0/0/2.1  191.22.3.2	     6345              
24041  Aggregate   vrf1601: Per-VRF Aggr[V]   \
                                      vrf1601                      7950400999

  • Verify if label is updated in the hardware: 

    
Router-PE1#show mpls forwarding labels 24001 hardware egress

Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ------------
24039  24167       20.20.20.1/32      Hu0/0/0/2    191.22.1.2      N/A         
	   24167	   20.20.20.1/32	  Hu0/0/0/2.1  191.22.3.2	   N/A

 Show-data Print at RPLC 
 
 LEAF - HAL pd context : 
 sub-type : MPLS, ecd_marked:0, has_collapsed_ldi:0
 collapse_bwalk_required:0, ecdv2_marked:0

Leaf H/W Result:

Leaf H/W Result on NP:0
Label           SwitchAction      EgressIf      Programmed
24039                      0    0x    200185    Programmed

nrLDI eng ctx:
     flags: 0x101, proto: 2, npaths: 0, nbuckets: 1
    ldi_tbl_idx: 0xc37e40, ecd_ref_cft: 0
    pbts_ldi_tbl_idx: 0x0, fastnrldi:0x0 

NR-LDI H/W Result for path 0 [index: 0xc37e40 (BE),  common to all NPs]:
          
 ECMP Sw Idx: 12811840 HW Idx: 200185 Path Idx: 0

NR-LDI H/W Result for path 1 [index: 0xc37e41 (BE),  common to all NPs]:

 ECMP Sw Idx: 12811841 HW Idx: 200185 Path Idx: 1

SHLDI eng ctx:
    flags: 0x0, shldi_tbl_idx: 0, num_entries:0

SHLDI HW data for path 0 [index: 0 (BE)] (common to all NPs):
Unable to get HW NRLDI Element rc: 1165765120NRLDI Idx: 0
SHLDI HW data for path 1 [index: 0x1 (BE)] (common to all NPs):
Unable to get HW NRLDI Element rc: 1165765120NRLDI Idx: 1

TX H/W Result for NP:0 (index: 0x187a0 (BE)):

 Next Hop Data
 Next Hop Valid:         YES
 Next Hop Index:         100256
 Egress Next Hop IF:     100047
 Hw Next Hop Intf:       606
 HW Port:                0
 Next Hop Flags:         COMPLETE 
 Next Hop MAC:           e4aa.5d9a.5f2e

NHINDEX H/W Result for NP:0 (index: 0 (BE)):
NhIndex is NOT required on this platform

NHINDEX STATS: pkts 0, bytes 0 (no stats)

RX H/W Result on NP:0 [Adj ptr:0x40 (BE)]:
Rx-Adj is NOT required on this platform

TX H/W Result for NP:0 (index: 0x189a8 (BE)):

 Next Hop Data
 Next Hop Valid:         YES
 Next Hop Index:         100776
 Egress Next Hop IF:     100208
 Hw Next Hop Intf:       607
 HW Port:                0
 Next Hop Flags:         COMPLETE 
 Next Hop MAC:           e4aa.5d9a.5f2d

NHINDEX H/W Result for NP:0 (index: 0 (BE)):
NhIndex is NOT required on this platform

NHINDEX STATS: pkts 0, bytes 0 (no stats)

RX H/W Result on NP:0 [Adj ptr:0x40 (BE)]:
Rx-Adj is NOT required on this platform

Verify the Overlay (L3VPN)

Imposition Path

  • Verify if the BGP neighbor connection is established with the respective neighbor node: 

    
Router-PE1#show bgp summary
BGP router identifier 13.13.13.1, local AS number 2001
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0xe0000000   RD version: 18003
BGP main routing table version 18003
BGP NSR Initial initsync version 3 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs

BGP is operating in STANDALONE mode.

Process       RcvTblVer   bRIB/RIB   LabelVer  ImportVer  SendTblVer  StandbyVer
Speaker           18003      18003      18003      18003       18003           0

Neighbor        Spk    AS MsgRcvd MsgSent   TblVer  InQ OutQ  Up/Down  St/PfxRcd
21.21.21.1        0  2001   19173    7671    18003    0    0    1d07h       4000
192.13.2.149      0  7001    4615    7773    18003    0    0 09:26:21        125

  • Verify if BGP routes are advertised and learnt: 

    
Router-PE1#show bgp vpnv4 unicast
BGP router identifier 13.13.13.1, local AS number 2001
BGP generic scan interval 60 secs
Non-stop routing is enabled
BGP table state: Active
Table ID: 0x0   RD version: 0
BGP main routing table version 305345
BGP NSR Initial initsync version 12201 (Reached)
BGP NSR/ISSU Sync-Group versions 0/0
BGP scan interval 60 secs

Status codes: s suppressed, d damped, h history, * valid, > best
              i - internal, r RIB-failure, S stale, N Nexthop-discard
Origin codes: i - IGP, e - EGP, ? - incomplete
   Network            Next Hop            Metric LocPrf Weight Path
Route Distinguisher: 2001:1601 (default for vrf vrf1601)
*> 20.13.1.1/32       192.13.26.5                            0 7501 i
*> 20.13.1.2/32       192.13.26.5                            0 7501 i
*>i20.23.1.1/32       20.20.20.1                    100      0 6553700 11501 i
*>i20.23.1.2/32       20.20.20.1                    100      0 6553700 11501 i

  • Verify BGP labels: 

    
Router-PE1#show bgp label table
Label   Type               VRF/RD         Context
24041   IPv4 VRF Table   vrf1601          -
24042   IPv4 VRF Table   vrf1602          -

  • Verify if the route is downloaded in the respective VRF: 

    
Router-PE1#show cef vrf vrf1601 20.23.1.1
20.23.1.1/32, version 743, internal 0x5000001 0x0 (ptr 0x8f932174) [1], 0x0 (0x8fa99990), 0xa08 (0x8f9fba58)
 Updated Apr 20 12:33:47.840
 Prefix Len 32, traffic index 0, precedence n/a, priority 3
   via 20.20.20.1/32, 3 dependencies, recursive [flags 0x6000]
    path-idx 0 NHID 0x0 [0x8c0e3148 0x0]
    recursion-via-/32
    next hop VRF - 'default', table - 0xe0000000
    next hop 20.20.20.1/32 via 24039/0/21
    next hop 191.23.1.2/32 Hu0/0/1/1    labels imposed {24059 24031}
Disposition Path

  • Verify if the imposition and disposition labels are assigned and label bindings are exchanged for L3VPN prefixes: 

    
Router-PE2#show mpls lsd forwarding
In_Label, (ID), Path_Info: <Type>
24030, (IPv4, 'default':4U, 13.13.13.1/32), 5 Paths
   1/1: IPv4, 'default':4U, Hu0/0/0/19.2, nh=191.31.1.93, lbl=24155,
            flags=0x0, ext_flags=0x0 
24031, (VPN-VRF, 'vrf1601':4U), 1 Paths
   1/1: PopLkup-v4, 'vrf1601':4U, ipv4 
24032, (VPN-VRF, 'vrf1602':4U), 1 Paths
   1/1: PopLkup-v4, 'vrf1602':4U, ipv4

  • Verify if the label update is received by the FIB: 

    

Router-PE2#show mpls forwarding
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ------------         
24019  Pop         18.18.18.3/32      Hu0/0/0/19   191.31.1.89     11151725032                   
24030  24155       13.13.13.1/32      Hu0/0/0/19   191.31.1.89     3639895                  
24031  Aggregate   vrf1601: Per-VRF Aggr[V]   \
                                     vrf1601                       32167647049

VRF-lite

VRF-lite is the deployment of VRFs without MPLS. VRF-lite allows a service provider to support two or more VPNs with overlapping IP addresses. With this feature, multiple VRF instances can be supported in customer edge devices.

VRF-lite interfaces must be Layer 3 interface and this interface cannot belong to more than one VRF at any time. Multiple interfaces can be part of the same VRF, provided all of them participate in the same VPN.

Configure VRF-lite

Consider two customers having two VPN sites each, that are connected to the same PE router. VRFs are used to create a separate routing table for each customer. We create one VRF for each customer (say, vrf1 and vrf2) and then add the corresponding interfaces of the router to the respective VRFs. Each VRF has its own routing table with the interfaces configured under it. The global routing table of the router does not show these interfaces, whereas the VRF routing table shows the interfaces that were added to the VRF. PE routers exchange routing information with CE devices by using static routing or a routing protocol such as BGP or RIP.

To summarize, VRF-lite configuration involves these main tasks:

  • Create VRF

  • Configure VRF under the interface

  • Configure VRF under routing protocol

Configuration Example

  • Create VRF: 

    
Router#configure
Router(config)#vrf vrf1
Router(config-vrf)#address-family ipv4 unicast
/* You must create route-policy pass-all before this configuration */
Router(config-vrf-af)#import from default-vrf route-policy pass-all
Router(config-vrf-af)#import route-target
Router(config-vrf-import-rt)#100:100
Router(config-vrf-import-rt)#exit
Router(config-vrf-af)#export route-target
Router(config-vrf-import-rt)#100:100
Router(config-vrf-import-rt)#exit
Router(config-vrf-import-rt)#commit

    Similarly create vrf2, with route-target as 100:100.

  • Configure VRF under the interface: 

    
Router#configure
Router(config)#interface TenGigE0/0/0/0.2001
Router(config-subif)#vrf vrf1
Router(config-subif)#ipv4 address 192.0.2.2 255.255.255.252
Router(config-subif)#encapsulation dot1q 2001
Router(config-subif)#exit

Router(config)#interface TenGigE0/0/0/0.2000
Router(config-subif)#vrf vrf2
Router(config-subif)#ipv4 address 192.0.2.5/30 255.255.255.252
Router(config-subif)#encapsulation dot1q 2000
Router(config-vrf-import-rt)#commit

    Similarly configure vrf1 under interface TenGigE0/0/0/1.2001 and vrf2 under interface TenGigE0/0/0/1.2000

  • Configure VRF under routing protocol: 

    
Router#configure
Router(config)#router rip
Router(config-rip)#vrf vrf1
Router(config-rip-vrf)#interface TenGigE0/0/0/0.2001
Router(config-rip-vrf-if)#exit
Router(config-rip-vrf)#interface TenGigE0/0/0/1.2001
Router(config-rip-vrf-if)#exit
Router(config-rip-vrf)#default-information originate
Router(config-vrf-import-rt)#commit

    Similarly configure vrf2 under rip, with

Running Configuration 


/* VRF Configuration */

vrf vrf1
address-family ipv4 unicast
  import route-target
   100:100
  !
  export route-target
   100:100
  !
!
!
vrf vrf2
address-family ipv4 unicast
  import route-target
   100:100
  !
  export route-target
   100:100
  !
!
!


/* Interface Configuration */

interface TenGigE0/0/0/0.2001
vrf vrf1
ipv4 address 192.0.2.2 255.255.255.252
encapsulation dot1q 2001
!

interface TenGigE0/0/0/0.2000
vrf vrf2
ipv4 address 192.0.2.5/30 255.255.255.252
encapsulation dot1q 2000
!

interface TenGigE0/0/0/1.2001
vrf vrf1
ipv4 address 203.0.113.2 255.255.255.252
encapsulation dot1q 2001
!

interface TenGigE0/0/0/1.2000
vrf vrf2
ipv4 address 203.0.113.5 255.255.255.252
encapsulation dot1q 2000
!

/* Routing Protocol Configuration */
router rip
interface Loopback0
!
interface TenGigE0/0/0/0
!
interface TenGigE0/0/0/0.2000
!
interface TenGigE0/0/0/0.2001
!
interface TenGigE0/0/0/1
!
interface TenGigE0/0/0/1.2000
!
interface TenGigE0/0/0/1.2001
!

vrf vrf1
  interface TenGigE0/0/0/0.2001
  !
  interface TenGigE0/0/0/1.2001
  !
  default-information originate
 !
vrf vrf2
  interface TenGigE0/0/0/1.2000
  !
  interface TenGigE0/0/0/1.2000
  !
  default-information originate
 !

Verification


Router#show route vrf vrf1
Mon Jul  4 19:12:54.739 UTC

Codes: C - connected, S - static, R - RIP, B - BGP, (>) - Diversion path
       O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - ISIS, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, su - IS-IS summary null, * - candidate default
       U - per-user static route, o - ODR, L - local, G  - DAGR, l - LISP
       A - access/subscriber, a - Application route
       M - mobile route, r - RPL, (!) - FRR Backup path

Gateway of last resort is not set

C    203.0.113.0/24 is directly connected, 00:07:01, TenGigE0/0/0/1.2001
L    203.0.113.2/30 is directly connected, 00:07:01, TenGigE0/0/0/1.2001
C    192.0.2.0/24 is directly connected, 00:05:51, TenGigE0/0/0/1.2001
L    192.0.2.2/30 is directly connected, 00:05:51, TenGigE0/0/0/1.2001



Router#show route vrf vrf2
Mon Jul  4 19:12:59.121 UTC

Codes: C - connected, S - static, R - RIP, B - BGP, (>) - Diversion path
       O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - ISIS, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, su - IS-IS summary null, * - candidate default
       U - per-user static route, o - ODR, L - local, G  - DAGR, l - LISP
       A - access/subscriber, a - Application route
       M - mobile route, r - RPL, (!) - FRR Backup path

Gateway of last resort is not set

R    198.51.100.53/30 [120/1] via 192.0.2.1, 00:01:42, TenGigE0/0/0/0.2000
C    203.0.113.0/24 is directly connected, 00:08:43, TenGigE0/0/0/1.2000
L    203.0.113.5/30 is directly connected, 00:08:43, TenGigE0/0/0/1.2000
C    192.0.2.0/24 is directly connected, 00:06:17, TenGigE0/0/0/0.2000
L    192.0.2.5/30 is directly connected, 00:06:17, TenGigE0/0/0/0.2000

Related Topics

Associated Commands

MPLS L3VPN Services using Segment Routing

Currently, MPLS Label Distribution Protocol (LDP) is the widely used transport for MPLS L3VPN services. The user can achieve better resilience and convergence for the network traffic, by transporting MPLS L3VPN services using Segment Routing (SR), instead of MPLS LDP. Segment routing can be directly applied to the MPLS architecture without changing the forwarding plane. In a segment-routing network using the MPLS data plane, LDP or other signaling protocol is not required; instead label distribution is performed by IGP (IS-IS or OSPF) or BGP protocol. Removing protocols from the network simplifies its operation and makes it more robust and stable by eliminating the need for protocol interaction. Segment routing utilizes the network bandwidth more effectively than traditional MPLS networks and offers lower latency.

Configure MPLS L3VPN over Segment Routing

Topology

Given below is a network scenario, where MPLS L3VPN service is transported using Segment Routing.

Figure 7. MPLS L3VPN over Segment Routing


In this topology, CE1 and CE2 are the two customer routers. ISP has two PE routers, PE1 and PE2 and a P router. RIP is used for the edge protocol support between the CE and PE routers. Label distribution can be performed by IGP (IS-IS or OSPF) or BGP. OSPF is used in this scenario.

Customer's autonomous system is 65534, which peers with ISP's autonomous system 65000. This must be a vrf peering to prevent route advertisement into the global IPv4 table. The ISP routers PE1 and PE2 contain the VRF (for example, vrf1601) for the customer. PE1 and PE2 export and import the same route targets, although this is not necessary.

Loopback interfaces are used in this topology to simulate the attached networks.

Configuration

You must complete these tasks to ensure the successful configuration of MPLS L3VPN over segment routing:

Configure Segment Routing in MPLS Core

This section takes you through the configuration procedure to enable segment routing in MPLS core. You must perform this configuration in PE1, P and PE2 routers in the topology, using the corresponding values.

Configuration Example 

/* Configure Segment Routing using OSFP */

Router-PE1#configure
Router-PE1(config)# router ospf dc-sr
Router-PE1(config-ospf)#router-id 13.13.13.1
Router-PE1(config-ospf)#segment routing mpls
Router-PE1(config-ospf)#segment routing forwarding mpls
Router-PE1(config-ospf)#mpls ldp sync
Router-PE1(config-ospf)#mpls ldp auto-config
Router-PE1(config-ospf)#segment-routing mpls sr-prefer
Router-PE1(config-ospf)#segment-routing prefix-sid-map advertise-local
Router-PE1(config-ospf)#exit
Router-PE1(config-ospf)#area 1
Router-PE1(config-ospf-ar)#interface HundredGigE0/0/0/2
Router-PE1(config-ospf-ar-if)#exit
Router-PE1(config-ospf-ar)#interface Loopback0
Router-PE1(config-ospf-ar-if)#prefix-sid index 1
Router-PE1(config-ospf-ar-if)#commit

/ * Configure segment routing global block */

Router# configure
Router(config)# segment-routing
Router(config-sr)# global-block 180000 200000
Router(config-sr)# commit
Router(config-sr)# exit


/* Configure Segment Routing using ISIS */

Router# configure
Router(config)# router isis ring
Router(config-isis)# is-type level-2-only
Router(config-isis)# net 49.0001.1921.6800.1001.00
Router(config-isis)# nsr
Router(config-isis)# distribute link-state
Router(config-isis)# nsf cisco
Router(config-isis)# address-family ipv4 unicast
Router(config-isis-af)# metric-style wide
Router(config-isis-af)# mpls traffic-eng level-1
Router(config-isis-af)# mpls traffic-eng router-id loopback0
Router(config-isis-af)# segment-routing mpls
Router(config-isis-af)# exit
!
Router(config-isis)# interface loopback0
Router(config-isis-if)# address-family ipv4 unicast
Router(config-isis-af)# prefix-sid index 30101
Router(config-isis-af)# exit
Running Configuration

PE1: 


router ospf dc-sr
 router-id 13.13.13.1
 segment-routing mpls
 segment-routing forwarding mpls
 mpls ldp sync
 mpls ldp auto-config
 segment-routing mpls sr-prefer
 segment-routing prefix-sid-map receive
 segment-routing prefix-sid-map advertise-local
 !
 area 1
  interface HundredGigE0/0/0/2
  !
  interface Loopback0
   prefix-sid index 1
  !
 !
!

configure
 segment-routing
  global-block 180000 200000
 !
!

configure
 router isis ring
  net 49.0001.1921.6800.1001.00
  nsr
  distribute link-state
  nsf cisco
  address-family ipv4 unicast
   metric-style wide
   mpls traffic-eng level-1
   mpls traffic-eng router-id Loopback0
   segment-routing mpls
 !
 interface Loopback0
  address-family ipv4 unicast
   prefix-sid index 30101
  !
 !

P node: 


router ospf dc-sr
 router-id 16.16.16.1
 segment-routing mpls
 segment-routing forwarding mpls
 mpls ldp sync
 mpls ldp auto-config
 segment-routing mpls sr-prefer
 segment-routing prefix-sid-map receive
 segment-routing prefix-sid-map advertise-local
 !
 area 1
  interface HundredGigE0/0/1/0
  !
  interface HundredGigE0/0/1/1
  !
  interface Loopback0
   prefix-sid index 1
  !
 !
!

configure
 segment-routing
  global-block 180000 200000
 !
!

configure
 router isis ring
  net 49.0001.1921.6800.1002.00
  nsr
  distribute link-state
  nsf cisco
  address-family ipv4 unicast
   metric-style wide
   mpls traffic-eng level-1
   mpls traffic-eng router-id Loopback0
   segment-routing mpls
 !
 interface Loopback0
  address-family ipv4 unicast
   prefix-sid index 30102
  !
 !

PE2: 


router ospf dc-sr
 router-id 20.20.20.1
 segment-routing mpls
 segment-routing forwarding mpls
 mpls ldp sync
 mpls ldp auto-config
 segment-routing mpls sr-prefer
 segment-routing prefix-sid-map receive
 segment-routing prefix-sid-map advertise-local
 !
 area 0
  interface HundredGigE0/0/0/19
  !
  interface Loopback0
   prefix-sid index 1
  !
 !
!

configure
 segment-routing
  global-block 180000 200000
 !
!

configure
 router isis ring
  net 49.0001.1921.6800.1003.00
  nsr
  distribute link-state
  nsf cisco
  address-family ipv4 unicast
   metric-style wide
   mpls traffic-eng level-1
   mpls traffic-eng router-id Loopback0
   segment-routing mpls
 !
 interface Loopback0
  address-family ipv4 unicast
   prefix-sid index 30103
  !
Related Topics

You must perform these tasks as well to complete the MPLS L3VPN configuration over segment routing:

Associated Commands

The applicable segment routing commands are described in the Segment Routing Command Reference for Cisco NCS 5500 Series Routers

Verify MPLS L3VPN Configuration over Segment Routing

  • Verify the statistics in core router and ensure that the counter for IGP transport label (64003 in this example) is increasing:

    P node: 

    
Router-P#show mpls forwarding
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ---------
64003  Pop         SR Pfx (idx 0)     Hu0/0/0/0   193.16.1.2      572842

  • Verify the statistics in PE1 router:

    PE1: 

    
Router-P#show mpls forwarding
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ ------------    --------
64001  60003       SR Pfx (idx 0)     Hu0/0/0/2    191.22.1.2      532978

  • Verify the statistics in PE2 router and ensure that the counter for the VPN label (24031 in this example) is increasing:

    PE2: 

    
Router-PE2#show mpls forwarding
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ---------
24031  Aggregate   vrf1601: Per-VRF Aggr[V]   \
                                      vrf1601                      501241

Also, refer Verify MPLS L3VPN Configuration for a detailed list of commands and sample outputs.

Implementing MPLS L3VPNs - References

MPLS L3VPN Benefits

MPLS L3VPN provides the following benefits:

  • Service providers can deploy scalable VPNs and deliver value-added services.

  • Connectionless service guarantees that no prior action is necessary to establish communication between hosts.

  • Centralized Service: Building VPNs in Layer 3 permits delivery of targeted services to a group of users represented by a VPN.

  • Scalability: Create scalable VPNs using connection-oriented and point-to-point overlays.

  • Security: Security is provided at the edge of a provider network (ensuring that packets received from a customer are placed on the correct VPN) and in the backbone.

  • Integrated Quality of Service (QoS) support: QoS provides the ability to address predictable performance and policy implementation and support for multiple levels of service in an MPLS VPN.

  • Straightforward Migration: Service providers can deploy VPN services using a straightforward migration path.

  • Migration for the end customer is simplified. There is no requirement to support MPLS on the CE router and no modifications are required for a customer intranet.

Major Components of MPLS L3VPN—Details

Virtual Routing and Forwarding Tables

Each VPN is associated with one or more VPN routing and forwarding (VRF) instances. A VRF defines the VPN membership of a customer site attached to a PE router. A VRF consists of the following components:

  • An IP version 4 (IPv4) unicast routing table

  • A derived FIB table

  • A set of interfaces that use the forwarding table

  • A set of rules and routing protocol parameters that control the information that is included in the routing table

These components are collectively called a VRF instance.

A one-to-one relationship does not necessarily exist between customer sites and VPNs. A site can be a member of multiple VPNs. However, a site can associate with only one VRF. A VRF contains all the routes available to the site from the VPNs of which it is a member.

Packet forwarding information is stored in the IP routing table and the FIB table for each VRF. A separate set of routing and FIB tables is maintained for each VRF. These tables prevent information from being forwarded outside a VPN and also prevent packets that are outside a VPN from being forwarded to a router within the VPN.

VPN Routing Information: Distribution

The distribution of VPN routing information is controlled through the use of VPN route target communities, implemented by BGP extended communities. VPN routing information is distributed as follows:

  • When a VPN route that is learned from a CE router is injected into a BGP, a list of VPN route target extended community attributes is associated with it. Typically, the list of route target community extended values is set from an export list of route targets associated with the VRF from which the route was learned.

  • An import list of route target extended communities is associated with each VRF. The import list defines route target extended community attributes that a route must have for the route to be imported into the VRF. For example, if the import list for a particular VRF includes route target extended communities A, B, and C, then any VPN route that carries any of those route target extended communities—A, B, or C—is imported into the VRF.

BGP Distribution of VPN Routing Information

A PE router can learn an IP prefix from the following sources:

  • A CE router by static configuration

  • An eBGP session with the CE router

  • Open Shortest Path First (OSPF) and RIP as Interior Gateway Protocols (IGPs)

The IP prefix is a member of the IPv4 address family. After the PE router learns the IP prefix, the PE converts it into the VPN-IPv4 prefix by combining it with a 64-bit route distinguisher. The generated prefix is a member of the VPN-IPv4 address family. It uniquely identifies the customer address, even if the customer site is using globally nonunique (unregistered private) IP addresses. The route distinguisher used to generate the VPN-IPv4 prefix is specified by the rd command associated with the VRF on the PE router.

BGP distributes reachability information for VPN-IPv4 prefixes for each VPN. BGP communication takes place at two levels:

  • Internal BGP (iBGP)—within the IP domain, known as an autonomous system.

  • External BGP (eBGP)—between autonomous systems.

BGP propagates reachability information for VPN-IPv4 prefixes among PE routers by the BGP protocol extensions (see RFC 2283, Multiprotocol Extensions for BGP-4), which define support for address families other than IPv4. Using the extensions ensures that the routes for a given VPN are learned only by other members of that VPN, enabling members of the VPN to communicate with each other.

MPLS Forwarding

Based on routing information stored in the VRF IP routing table and the VRF FIB table, packets are forwarded to their destination using MPLS.

A PE router binds a label to each customer prefix learned from a CE router and includes the label in the network reachability information for the prefix that it advertises to other PE routers. When a PE router forwards a packet received from a CE router across the provider network, it labels the packet with the label learned from the destination PE router. When the destination PE router receives the labeled packet, it pops the label and uses it to direct the packet to the correct CE router. Label forwarding across the provider backbone is based on dynamic label switching. A customer data packet carries two levels of labels when traversing the backbone:

  • The top label directs the packet to the correct PE router.

  • The second label indicates how that PE router should forward the packet to the CE router.

Automatic Route Distinguisher Assignment

To take advantage of iBGP load balancing, every network VRF must be assigned a unique route distinguisher. VRF is require a route distinguisher for BGP to distinguish between potentially identical prefixes received from different VPNs.

With thousands of routers in a network each supporting multiple VRFs, configuration and management of route distinguishers across the network can present a problem. Cisco IOS XR software simplifies this process by assigning unique route distinguisher to VRFs using the rd auto command.

To assign a unique route distinguisher for each router, you must ensure that each router has a unique BGP router-id. If so, the rd auto command assigns a Type 1 route distinguisher to the VRF using the following format: ip-address:number. The IP address is specified by the BGP router-id statement and the number (which is derived as an unused index in the 0 to 65535 range) is unique across theVRFs.

Finally, route distinguisher values are checkpointed so that route distinguisher assignment to VRF is persistent across failover or process restart. If an route distinguisher is explicitely configured for a VRF, this value is not overridden by the autoroute distinguisher.