IP Routing: EIGRP Configuration Guide, Cisco IOS Release 15M&T
EIGRP MPLS VPN PE-CE Site of Origin
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EIGRP MPLS VPN PE-CE Site of Origin

Contents

EIGRP MPLS VPN PE-CE Site of Origin

The EIGRP MPLS VPN PE-CE Site of Origin feature introduces the capability to filter Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) traffic on a per-site basis for Enhanced Interior Gateway Routing Protocol (EIGRP) networks. Site of Origin (SoO) filtering is configured at the interface level and is used to manage MPLS VPN traffic and to prevent transient routing loops from occurring in complex and mixed network topologies. This feature is designed to support the MPLS VPN Support for EIGRP Between Provider Edge (PE) and Customer Edge (CE) feature. Support for backdoor links is provided by this feature when a Cisco IOS release is implemented on PE routers that support EIGRP MPLS VPNs.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and 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 module.

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.

Prerequisites for EIGRP MPLS VPN PE-CE Site of Origin

This document assumes that Border Gateway Protocol (BGP) is configured in the network core (or the service provider backbone). The following tasks will also need to be completed before you can configure this feature:

  • This feature was introduced to support the MPLS VPN Support for EIGRP Between Provider Edge and Customer Edge feature and should be configured after the EIGRP MPLS VPN is created.

  • All PE routers that are configured to support the EIGRP MPLS VPN must run a Cisco IOS release that provides support for the SoO extended community.

Restrictions for EIGRP MPLS VPN PE-CE Site of Origin

  • If a VPN site is partitioned and the SoO extended community attribute is configured on a backdoor router interface, the backdoor link cannot be used as an alternate path to reach prefixes originated in other partitions of the same site.

  • A unique SoO value must be configured for each individual VPN site. The same value must be configured on all provider edge and customer edge interfaces (if SoO is configured on the CE routers) that support the same VPN site.

Information About EIGRP MPLS VPN PE-CE Site of Origin

EIGRP MPLS VPN PE-CE Site of Origin Support Overview

The EIGRP MPLS VPN PE-CE Site of Origin feature introduces SoO support for EIGRP-to-BGP and BGP-to-EIGRP redistribution. The SoO extended community is a BGP extended community attribute that is used to identify routes that have originated from a site so that the readvertisement of that prefix back to the source site can be prevented. The SoO extended community uniquely identifies the site from which a PE router has learned a route. SoO support provides the capability to filter MPLS VPN traffic on a per-EIGRP-site basis. SoO filtering is configured at the interface level and is used to manage MPLS VPN traffic and to prevent routing loops from occurring in complex and mixed network topologies, such as EIGRP VPN sites that contain both VPN and backdoor links.

The configuration of the SoO extended community allows MPLS VPN traffic to be filtered on a per-site basis. The SoO extended community is configured in an inbound BGP route map on the PE router and is applied to the interface. The SoO extended community can be applied to all exit points at the customer site for more specific filtering but must be configured on all interfaces of PE routers that provide VPN services to CE routers.

Site of Origin Support for Backdoor Links

The EIGRP MPLS VPN PE-CE Site of Origin (SoO) feature introduces support for backdoor links. A backdoor link or a route is a connection that is configured outside of the VPN between a remote and main site; for example, a WAN leased line that connects a remote site to the corporate network. Backdoor links are typically used as back-up routes between EIGRP sites if the VPN link is down or not available. A metric is set on the backdoor link so that the route though the backdoor router is not selected unless there is a VPN link failure.

The SoO extended community is defined on the interface of the backdoor router. It identifies the local site ID, which should match the value that is used on the PE routers that support the same site. When the backdoor router receives an EIGRP update (or reply) from a neighbor across the backdoor link, the router checks the update for an SoO value. If the SoO value in the EIGRP update matches the SoO value on the local backdoor interface, the route is rejected and not added to the EIGRP topology table. This typically occurs when the route with the local SoO valued in the received EIGRP update was learned by the other VPN site and then advertised through the backdoor link by the backdoor router in the other VPN site. SoO filtering on the backdoor link prevents transient routing loops from occurring by filtering out EIGRP updates that contain routes that carry the local site ID.


Note


If a VPN site is partitioned and the SoO extended community attribute is configured on a backdoor router interface, the backdoor link cannot be used as an alternate path to reach prefixes originated in other partitions of the same site.


If this feature is enabled on the PE routers and the backdoor routers in the customer sites, and SoO values are defined on both the PE and backdoor routers, both the PE and backdoor routers will support convergence between the VPN sites. The other routers in the customer sites need only propagate the SoO values carried by the routes, because the routes are forwarded to neighbors. These routers do not otherwise affect or support convergence beyond normal Diffusing Update Algorithm (DUAL) computations.

Router Interoperation with a Site of Origin Extended Community

The configuration of an SoO extended community allows routers that support the EIGRP MPLS VPN PE-CE Site of Origin feature to identify the site from which each route originated. When this feature is enabled, the EIGRP routing process on the PE or CE router checks each received route for the SoO extended community and filters based on the following conditions:

  • A received route from BGP or a CE router contains a SoO value that matches the SoO value on the receiving interface.

If a route is received with an associated SoO value that matches the SoO value that is configured on the receiving interface, the route is filtered because it was learned from another PE router or from a backdoor link. This behavior is designed to prevent routing loops.

  • A received route from a CE router is configured with an SoO value that does not match.

If a route is received with an associated SoO value that does not match the SoO value that is configured on the receiving interface, the route is added to the EIGRP topology table so that it can be redistributed into BGP.

If the route is already installed to the EIGRP topology table but is associated with a different SoO value, the SoO value from the topology table will be used when the route is redistributed into BGP.

  • A received route from a CE router does not contain an SoO value.

If a route is received without a SoO value, the route is accepted into the EIGRP topology table, and the SoO value from the interface that is used to reach the next hop CE router is appended to the route before it is redistributed into BGP.

When BGP and EIGRP peers that support the SoO extended community receive these routes, they will also receive the associated SoO values and pass them to other BGP and EIGRP peers that support the SoO extended community. This filtering is designed to prevent transient routes from being relearned from the originating site, which prevents transient routing loops from occurring.

Redistribution of BGP VPN Routes That Carry the Site of Origin into EIGRP

When an EIGRP routing process on a PE router redistributes BGP VPN routes into an EIGRP topology table, EIGRP extracts the SoO value (if one is present) from the appended BGP extended community attributes and appends the SoO value to the route before adding it to the EIGRP topology table. EIGRP tests the SoO value for each route before sending updates to CE routers. Routes that are associated with SoO values that match the SoO value configured on the interface are filtered out before they are passed to the CE routers. When an EIGRP routing process receives routes that are associated with different SoO values, the SoO value is passed to the CE router and carried through the CE site.

BGP Cost Community Support for EIGRP MPLS VPN PE-CE Network Topologies

The BGP cost community is a nontransitive extended community attribute that is passed to internal BGP (iBGP) and confederation peers but not external BGP (eBGP) peers. The cost community feature allows you to customize the local route preference and influence the BGP best path selection process.

Before BGP cost community support for EIGRP MPLS VPN PE-CE network topologies was introduced, BGP preferred locally sourced routes over routes learned from BGP peers. Backdoor links in an EIGRP MPLS VPN topology were preferred by BGP when the backdoor link was learned first. (A backdoor link or a route is a connection that is configured outside of the VPN between a remote and main site; for example, a WAN leased line that connects a remote site to the corporate network).

The “prebest path” point of insertion (POI) was introduced in the BGP Cost Community feature to support mixed EIGRP VPN network topologies that contain VPN and backdoor links. This POI is applied automatically to EIGRP routes that are redistributed into BGP. The “prebest path” POI carries the EIGRP route type and metric. This POI influences the best path calculation process by influencing BGP to consider this POI before any other comparison step. No configuration is required. This feature is enabled automatically for EIGRP VPN sites when a Cisco IOS release that supports this feature is installed on the PE routers or the CE and backdoor router at the customer sites.

For more information about the BGP Cost Community feature, see to the BGP Cost Community module in the Cisco IOS IP Routing: BGP Configuration Guide.

Benefits of the EIGRP MPLS VPN PE-CE Site of Origin Support Feature

The configuration of the EIGRP MPLS VPN PE-CE Site of Origin Support feature introduces per-site VPN filtering, which improves support for complex topologies, such as MPLS VPNs with backdoor links, CE routers that are dual-homed to different PE routers, and PE routers that support CE routers from different sites within the same virtual routing and forwarding (VRF) instance.

How to Configure EIGRP MPLS VPN PE-CE Site of Origin Support

Configuring the Site of Origin Extended Community

The configuration of the SoO extended community allows MPLS VPN traffic to be filtered on a per-site basis. The SoO extended community is configured in an inbound BGP route map on the PE router and is applied to the interface. The SoO extended community can be applied to all exit points at the customer site for more specific filtering but must be configured on all interfaces of PE routers that provide VPN services to CE routers.

Before You Begin
  • Border Gateway Protocol (BGP) is configured in the network core (or the service provider backbone).

  • Configure an EIGRP MPLS VPN before configuring this feature.

  • All PE routers that are configured to support the EIGRP MPLS VPN must support the SoO extended community.

  • A unique SoO value must be configured for each VPN site. The same value must be used on the interface of the PE router that connects to the CE router for each VPN site.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    route-map map-name {permit | deny} [sequence-number]

    4.    set extcommunity {rt extended-community-value [additive] | soo extended-community-value}

    5.    exit

    6.    interface type number

    7.    ip vrf forwarding vrf-name

    8.    ip vrf sitemap route-map-name

    9.    ip address ip-address subnet-mask

    10.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 route-map map-name {permit | deny} [sequence-number]


    Example:
    Router(config)# route-map Site-of-Origin permit 10
     

    Enters route-map configuration mode and creates a route map.

    • The route map is created in this step so that SoO extended community can be applied.

     
    Step 4 set extcommunity {rt extended-community-value [additive] | soo extended-community-value}


    Example:
    Router(config-route-map)# set extcommunity soo 100:1 


    Example:
    
    
            
     

    Sets BGP extended community attributes.

    • The rt keyword specifies the route target extended community attribute.

    • The soo keyword specifies the site of origin extended community attribute.

    • The extended-community-valueargument specifies the value to be set. The value can be one of the following formats:
      • autonomous-system-number: network-number
      • ip-address: network-number

    The colon is used to separate the autonomous system number and network number or IP address and network number.

    • The additive keyword adds a route target to the existing route target list without replacing any existing route targets.

     
    Step 5 exit


    Example:
    Router(config-route-map)# exit
     

    Exits route-map configuration mode and enters global configuration mode.

     
    Step 6 interface type number


    Example:
    Router(config)# interface FastEthernet 0/0
     

    Enters interface configuration mode to configure the specified interface.

     
    Step 7 ip vrf forwarding vrf-name


    Example:
    Router(config-if)# ip vrf forwarding VRF1 
     

    Associates the VRF with an interface or subinterface.

    • The VRF name configured in this step should match the VRF name created for the EIGRP MPLS VPN with the MPLS VPN Support for EIGRP Between Provider Edge and Customer Edge feature.

     
    Step 8 ip vrf sitemap route-map-name


    Example:
    Router(config-if)# ip vrf sitemap Site-of-Origin 
     

    Associates the VRF with an interface or subinterface.

    • The route map name configured in this step should match the route map name created to apply the SoO extended community in Step 3.

     
    Step 9 ip address ip-address subnet-mask


    Example:
    Router(config-if)# ip address 10.0.0.1 255.255.255.255
     

    Configures the IP address for the interface.

    • The IP address needs to be reconfigured after enabling VRF forwarding.

     
    Step 10 end


    Example:
    Router(config-if)# end
     

    Exits interface configuration mode and enters privileged EXEC mode.

     

    What to Do Next

    • For mixed EIGRP MPLS VPN network topologies that contain backdoor routes, the next task is to configure the “prebest path” cost community for backdoor routes.

    Verifying the Configuration of the Site of Origin Extended Community

    Use the following steps to verify the configuration of the SoO extended community attribute.

    SUMMARY STEPS

      1.    enable

      2.    show ip bgp vpnv4 {all | rd route-distinguisher| vrf vrf-name} [ip-prefix / length [longer-prefixes] [output-modifiers]] [network-address [mask] [longer-prefixes] [output-modifiers]] [cidr-only] [community] [community-list] [dampened-paths] [filter-list] [flap-statistics] [inconsistent-as] [neighbors] [paths [line]] [peer-group] [quote-regexp] [regexp] [summary] [tags]

      3.    show eigrp address-family {ipv4 | ipv6} [vrf vrf-name] [autonomous-system-number] [multicast] topology [topology-name] [ip-address] [active] [all-links] [detail-links] [pending] [summary] [zero-successors] [route-type{connected | external | internal | local | redistributed | summary | vpn}]


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 show ip bgp vpnv4 {all | rd route-distinguisher| vrf vrf-name} [ip-prefix / length [longer-prefixes] [output-modifiers]] [network-address [mask] [longer-prefixes] [output-modifiers]] [cidr-only] [community] [community-list] [dampened-paths] [filter-list] [flap-statistics] [inconsistent-as] [neighbors] [paths [line]] [peer-group] [quote-regexp] [regexp] [summary] [tags]


      Example:
      Router# show ip bgp vpnv4 all 10.0.0.1 
       

      Displays VPN address information from the BGP table.

      • Use the show ip bgp vpnv4 command with the all keyword to verify that the specified route has been configured with the SoO extended community attribute.

       
      Step 3 show eigrp address-family {ipv4 | ipv6} [vrf vrf-name] [autonomous-system-number] [multicast] topology [topology-name] [ip-address] [active] [all-links] [detail-links] [pending] [summary] [zero-successors] [route-type{connected | external | internal | local | redistributed | summary | vpn}]


      Example:
      Router# show eigrp address-family ipv4 4453 topology 10.10.10.0/24
       

      Displays entries in the EIGRP topology table.

       

      Configuration Examples for EIGRP MPLS VPN PE-CE SoO

      Example Configuring the Site of Origin Extended Community

      The following example, beginning in global configuration mode, configures the SoO extended community on an interface:

      Router(config)# route-map Site-of-Origin permit 10 
      Router(config-route-map)# set extcommunity soo 100:1 
      Router(config-route-map)# exit
       
      Router(config)# interface FastEthernet 0/0 
      Router(config-if)# ip vrf forwarding VRF1 
      Router(config-if)# ip vrf sitemap Site-of-Origin 
      Router(config-if)# ip address 10.0.0.1 255.255.255.255
       
      Router(config-if)# end
       

      Example Verifying the Site of Origin Extended Community

      The following example shows VPN address information from the BGP table and verifies the configuration of the SoO extended community:

      Router# show ip bgp vpnv4 all 10.0.0.1 
      BGP routing table entry for 100:1:10.0.0.1/32, version 6
      Paths: (1 available, best #1, no table)
        Advertised to update-groups:
           1         
        100 300
          192.168.0.2 from 192.168.0.2 (172.16.13.13)
            Origin incomplete, localpref 100, valid, external, best
            Extended Community: SOO:100:1
      

      The following example shows how to display EIGRP metrics for specified internal services and external services:

      Router# show eigrp address-family ipv4 4453 topology 10.10.10.0/24
      EIGRP-IPv4 VR(virtual-name) Topology Entry for AS(4453)/ID(10.0.0.1) for 10.10.10.0/24 
        State is Passive, Query origin flag is 1, 1 Successor(s), FD is 128256 
        Descriptor Blocks: 
        0.0.0.0 (Null0), from Connected, Send flag is 0x0 
            Composite metric is (128256/0), service is Internal 
            Vector metric: 
              Minimum bandwidth is 10000000 Kbit 
              Total delay is 5000 microseconds 
              Reliability is 255/255 
              Load is 1/255 
              Minimum MTU is 1514 
              Hop count is 0 
              Originating router is 10.0.0.1

      Additional References

      Related Documents

      Related Topic

      Document Title

      Cisco IOS commands

      Cisco IOS Master Commands List, All Releases

      BGP cost community feature and the “prebest path” point of insertion

      BGP Cost Community module of the Cisco IOS IP Routing: BGP Configuration Guide

      Cisco Express Forwarding (CEF) commands

      Cisco IOS IP Switching Command Reference

      CEF configuration tasks

      Cisco Express Forwarding Overview module of the Cisco IOS IP Switching Configuration Guide

      EIGRP commands

      Cisco IOS IP Routing: EIGRP Command Reference

      EIGRP configuration tasks

      Configuring EIGRP

      MPLS VPNs

      Cisco IOS Multiprotocol Label Switching Configuration Guide

      Standards

      Standard

      Title

      None

      --

      MIBs

      MIB

      MIBs Link

      None

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

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

      RFCs

      RFC

      Title

      None

      --

      Technical Assistance

      Description

      Link

      The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

      http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

      Feature Information for MPLS VPN PE-CE Site of Origin (SoO)

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

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

      Table 1 Feature Information for EIGRP MPLS VPN PE-CE Site of Origin (SoO)

      Feature Name

      Releases

      Feature Information

      EIGRP MPLS VPN PE-CE Site of Origin (SoO)

      12.0(27)S 12.2(18)SXE 12.2(28)SB 12.2(30)S 12.2(33)SRE 12.2(33)XNE 12.3(8)T 15.0(1)M

      The EIGRP MPLS VPN PE-CE Site of Origin (SoO) feature introduces the capability to filter MPLS VPN traffic on a per-site basis for EIGRP networks.

      The following command was introduced or modified by this feature: ip vrf sitemap

      Glossary

      AFI--Address Family Identifier. Carries the identity of the network layer protocol that is associated with the network address.

      backdoor link --A link connecting two backdoor routers.

      backdoor router --A router that connects two or more sites, that are also connected to each other through an MPLS VPN EIGRP PE to CE links.

      BGP --Border Gateway Protocol. An interdomain routing protocol that exchanges reachability information with other BGP systems. It is defined by RFC 1163, A Border Gateway Protocol (BGP). BGP supports CIDR and uses route aggregation mechanisms to reduce the size of routing tables.

      Cost Community --An extended community attribute that can be inserted anywhere into the best path calculation.

      customer edge (CE) router --A router that belongs to a customer network, that connects to a provider edge (PE) router to utilize MPLS VPN network services.

      MBGP --multiprotocol BGP. An enhanced version of BGP that carries routing information for multiple network-layer protocols and IP multicast routes. It is defined in RFC 2858, Multiprotocol Extensions for BGP-4.

      provider edge (PE) router --The PE router is the entry point into the service provider network. The PE router is typically deployed on the edge of the network and is administered by the service provider. The PE router is the redistribution point between EIGRP and BGP in PE to CE networking.

      site --A collection of routers that have well-defined exit points to other “sites.”

      site of origin (SoO) --A special purpose tag or attribute that identifies the site that injects a route into the network. This attribute is used for intersite filtering in MPLS VPN PE-to-CE topologies.

      VPN --Virtual Private Network. Allows IP traffic to travel securely over public TCP/IP networks and the Internet by encapsulating and encrypting all IP packets. VPN uses a tunnel to encrypt all information at the IP level.