Cisco IOS XE IP Routing Protocols Configuration Guide, Release 2
EIGRP MPLS VPN PE-CE Site of Origin (SoO)
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Table Of Contents

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

Finding Feature Information

Contents

Prerequisites for EIGRP MPLS VPN PE-CE SoO

Restrictions for EIGRP MPLS VPN PE-CE SoO

Information About EIGRP MPLS VPN PE-CE SoO

EIGRP MPLS VPN PE-CE SoO Support Overview

SoO Support for Back Door Links

Router Interoperation with the SoO Extended Community

Redistributing BGP VPN Routes That Carry the SoO into EIGRP

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

Benefits of the EIGRP MPLS VPN PE-CE SoO Support Feature

How to Configure EIGRP MPLS VPN PE-CE SoO Support

Configuring the SoO Extended Community

Prerequisites

Examples

What to Do Next

Verifying the Configuration of the SoO Extended Community

Examples

Additional References

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for EIGRP MPLS VPN PE-CE SoO

Glossary


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

Last Updated: May 4, 2009

The EIGRP MPLS VPN PE-CE Site of Origin (SoO) 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. 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 back door links is provided by this feature when installed on PE routers that support EIGRP MPLS VPNs.

Finding Feature Information

For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for EIGRP MPLS VPN PE-CE SoO" section.

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

Contents

•Prerequisites for EIGRP MPLS VPN PE-CE SoO

•Restrictions for EIGRP MPLS VPN PE-CE SoO

•Information About EIGRP MPLS VPN PE-CE SoO

•How to Configure EIGRP MPLS VPN PE-CE SoO Support

•Additional References

•Feature Information for EIGRP MPLS VPN PE-CE SoO

•Glossary

Prerequisites for EIGRP MPLS VPN PE-CE SoO

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 Cisco IOS XE Release 2.1 or a later release, which provides support for the SoO extended community.

Restrictions for EIGRP MPLS VPN PE-CE SoO

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

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

Information About EIGRP MPLS VPN PE-CE SoO

To configure this feature, you must understand the following concepts:

•EIGRP MPLS VPN PE-CE SoO Support Overview

•SoO Support for Back Door Links

•Router Interoperation with the SoO Extended Community

•Redistributing BGP VPN Routes That Carry the SoO into EIGRP

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

•Benefits of the EIGRP MPLS VPN PE-CE SoO Support Feature

EIGRP MPLS VPN PE-CE SoO Support Overview

The EIGRP MPLS VPN PE-CE SoO 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 re-advertisement 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 back door 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.

SoO Support for Back Door Links

The EIGRP MPLS VPN PE-CE SoO feature introduces support for back door links. A back door 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. Back door 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 back door link so that the route though the back door router is not selected unless there is a VPN link failure.

The SoO extended community is defined on the interface of the back door 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 back door router receives an EIGRP update (or reply) from a neighbor across the back door link, the router checks the update for a SoO value. If the SoO value in the EIGRP update matches the SoO value on the local back door interface, the route is rejected and not installed 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 back door link by the back door router in the other VPN site. SoO filtering on the back door 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 back door router interface, the back door link cannot be used as an alternate path to reach prefixes originated in other partition of the same site.

If this feature is enabled on the PE routers and the back door routers in the customer sites, and SoO values are defined on both the PE and back door routers, both the PE and back door 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, as the routes are forwarded to neighbors. These routers do not otherwise affect or support convergence beyond normal DUAL computations.

Router Interoperation with the SoO Extended Community

The configuration of the SoO extended community allows routers that support this 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 out because it was learned from another PE router or from a back door link. This behavior is designed to prevent routing loops.

•A received route from a CE router is configured with a 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 accepted into 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 a 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.

Redistributing BGP VPN Routes That Carry the SoO into EIGRP

When an EIGRP routing process on the PE router redistributes BGP VPN routes into the 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 installing 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 non-transitive 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 EIGRP SoO BGP Cost Community support was introduced, BGP preferred locally sourced routes over routes learned from BGP peers. Back door links in an EIGRP MPLS VPN topology were preferred by BGP when the back door link was learned first. (A back door 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 "pre-bestpath" point of insertion (POI) has been introduced in the BGP Cost Community feature to support mixed EIGRP VPN network topologies that contain VPN and back door links. This POI is applied automatically to EIGRP routes that are redistributed into BGP. The "pre-bestpath" 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 Cisco IOS XE Release 2.1 or later is installed to the PE routers or the CE and back door router at the customer sites.

For more information about the BGP Cost Community feature, refer to the BGP Cost Community module in the Cisco IOS XE IP Routing Protocols Configuration Guide, Release 2.

Benefits of the EIGRP MPLS VPN PE-CE SoO Support Feature

The configuration of the EIGRP MPLS VPN PE-CE Site of Origin (SoO) Support feature introduces per-site VPN filtering, which improves support for complex topologies, such as, MPLS VPNs with back door links, Customer Edge (CE) routers that are dual-homed to different Provider Edge (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 SoO Support

This section contains the following procedures:

•Configuring the SoO Extended Community

•Verifying the Configuration of the SoO Extended Community

Configuring the SoO 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.

Prerequisites

•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 Action
Purpose

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

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-value argument 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 RED

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.

Examples

The following example, beginning in global configuration mode, configures SoO filtering 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 RED 

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

What to Do Next

•To verify the configuration of the SoO extended community, follow the steps in the next section, "Verifying the Configuration of the SoO Extended Community."

•For mixed EIGRP MPLS VPN network topologies that contain back door routes, the next task is to configure the "pre-bestpath" cost community for back door routes.

Verifying the Configuration of the SoO 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]

DETAILED STEPS

 
Command or Action
Purpose

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.

Examples

This 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

Additional References

The following sections provide references related to the EIGRP MPLS VPN PE-CE SoO feature.

Related Documents

Related Topic
Document Title

BGP Cost Community feature and the "pre-bestpath" point of insertion

BGP Cost Community module

CEF commands

Cisco IOS IP Switching Command Reference

CEF configuration tasks

Cisco Express Forwarding Overview module

EIGRP commands

Cisco IOS IP Routing Protocols Command Reference

EIGRP configuration tasks

Configuring EIGRP

MPLS VPNs

MPLS Layer 3 VPNs module


Standards

Standard
Title

None

—


MIBs

MIB
MIBs Link

None

To locate and download MIBs for selected platforms, Cisco IOS XE 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 website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/techsupport


Feature Information for EIGRP MPLS VPN PE-CE SoO

Table 1 lists the release history for this feature.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE software release train also support that feature.

Table 1 Feature Information for EIGRP MPLS VPN PE-CE SoO 

Feature Name
Releases
Feature Information

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

Cisco IOS XE
Release 2.1

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

In Cisco IOS XE Release 2.1, this feature was introduced on the Cisco ASR 1000 Series Aggregation Services Routers.

The following commands were 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.

Back door link—A link connecting two back door routers.

Back door router—A router that connects two or more sites, which 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). The current implementation of BGP is BGP Version 4 (BGP4). BGP4 is the predominant interdomain routing protocol that is used on the Internet. It 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, which 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.

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