Load Sharing MPLS VPN Traffic

Last Updated: December 14, 2011

Load sharing distributes traffic so that no individual router is overburdened. In a Multiprotocol Label Switching (MPLS) Virtual Private Network (VPN) network, you can achieve load sharing through the following methods:

  • BGP multipath options
  • Directly connected loopback peering

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

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

Prerequisites for Load Sharing MPLS VPN Traffic

Before configuring load sharing, ensure that your MPLS VPN network (including MPLS VPN carrier supporting carrier or interautonomous system) is configured and working properly. See the Prerequisites for Load Sharing MPLS VPN Traffic for references related to MPLS VPNs.

Restrictions for Load Sharing MPLS VPN Traffic

  • Configuring BGP multipath for eBGP and iBGP is only for basic MPLS Layer 3 VPNs. MPLS VPN Inter-AS and MPLS VPN carrier supporting carrier do not support this multipath configuration.
  • With multiple iBGP paths installed in a routing table, a route reflector advertises only one of the paths (one next hop). If a router is behind a route reflector, all routers that are connected to multihomed sites are not advertised unless separate VRFs with different RDs are configured for each VRF.
  • Each IP routing table entry for a BGP prefix that has multiple iBGP paths uses additional memory. We recommend not using this feature on a router with a low amount of available memory and especially when the router is carrying a full Internet routing table.
  • eBGP Multipath is not supported on MPLS VPN Inter-AS with ASBRs that exchange VPNv4 routes.
  • Load sharing using directly connected loopback peering does not apply to CSC networks that use LDP and an IGP to distribute routes and MPLS labels.

When you configure static routes in an MPLS or MPLS VPN environment, some variations of the ip route and ip route vrf commands are not supported. These variations of the commands are not supported in Cisco IOS releases that support the Tag Forwarding Information Base (TFIB), specifically Cisco IOS Releases 12.nT, 12.nM, and 12.0S. The TFIB cannot resolve prefixes when the recursive route over which the prefixes travel disappears and then reappears. However, the command variations are supported in Cisco IOS releases that support the MPLS Forwarding Infrastructure (MFI), specifically Cisco IOS Release 12.2(25)S and later releases. Use the following guidelines when configuring static routes.

Supported Static Routes in an MPLS Environment

The following ip route command is supported when you configure static routes in an MPLS environment:

ip route destination-prefix mask interface next-hop-address

The following ip route commands are supported when you configure static routes in an MPLS environment and configure load sharing with static nonrecursive routes and a specific outbound interface:

ip route destination-prefix mask interface1 next-hop1

ip route destination-prefix mask interface2 next-hop2

Unsupported Static Routes in an MPLS Environment That Uses the TFIB

The following ip route command is not supported when you configure static routes in an MPLS environment:

ip route destination-prefix mask next-hop-address

The following ip route command is not supported when you configure static routes in an MPLS VPN environment and enable load sharing where the next hop can be reached through two paths:

ip route destination-prefix mask next-hop-address

The following ip route command is not supported when you configure static routes in an MPLS VPN environment and enable load sharing where the destination can be reached through two next hops:

ip route destination-prefix mask next-hop1

ip route destination-prefix mask next-hop2

Use the interface and next-hop arguments when specifying static routes.

Supported Static Routes in an MPLS VPN Environment

The following ip route vrf commands are supported when you configure static routes in an MPLS VPN environment, and the next hop and interface are associated with the same virtual routing and forwarding (VRF) instance:

    • ip route vrf vrf-name destination-prefix mask next-hop-address
    • ip route vrf vrf-name destination-prefix mask interface next-hop-address
    • ip route vrf vrf-name destination-prefix mask interface1 next-hop1

    • ip route vrf vrf-name destination-prefix mask interface2 next-hop2

The following ip route vrf commands are supported when you configure static routes in an MPLS VPN environment, and the next hop is in the global table in the MPLS cloud in the global routing table. For example, these commands are supported when the next hop is pointing to the internet gateway.

    • ip route vrf vrf-name destination-prefix mask next-hop-address global
    • ip route vrf vrf-name destination-prefix mask interface next-hop-address (This command is supported when the next hop and the interface are in the core.)

The following ip route commands are supported when you configure static routes in an MPLS VPN environment and enable load sharing with static nonrecursive routes and a specific outbound interfaces:

ip route destination-prefix mask interface1 next-hop1

ip route destination-prefix mask interface2 next-hop2

Unsupported Static Routes in an MPLS VPN Environment That Uses the TFIB

The following ip route command is not supported when you configure static routes in an MPLS VPN environment, the next hop is in the global table in the MPLS cloud within the core, and you enable load sharing where the next hop can be reached through two paths:

ip route vrf destination-prefix mask next-hop-address global

The following ip route commands are not supported when you configure static routes in an MPLS VPN environment, the next hop is in the global table in the MPLS cloud within the core, and you enable load sharing where the destination can be reached through two next hops:

ip route vrf destination-prefix mask next-hop1 global

ip route vrf destination-prefix mask next-hop2 global

The following ip route vrf commands are not supported when you configure static routes in an MPLS VPN environment, and the next hop and interface are in the same VRF:

ip route vrf vrf-name destination-prefix mask next-hop1

ip route vrf vrf-name destination-prefix mask next-hop2

Supported Static Routes in an MPLS VPN Environment Where the Next Hop Resides in the Global Table on the CE Router

The following ip route vrf command is supported when you configure static routes in an MPLS VPN environment, and the next hop is in the global table on the customer edge (CE) side. For example, the following command is supported when the destination-prefix is the CE router's loopback address, as in EBGP multihop cases.

ip route vrf vrf-name destination-prefix mask interface next-hop-address

The following ip route commands are supported when you configure static routes in an MPLS VPN environment, the next hop is in the global table on the CE side, and you enable load sharing with static nonrecursive routes and a specific outbound interfaces:

ip route destination-prefix mask interface1 nexthop1

ip route destination-prefix mask interface2 nexthop2

Information About Load Sharing MPLS VPN Traffic

Overview of Load Sharing Using BGP Multipath Options

A variety of Border Gateway Protocol (BGP) multipath options exist that enable you to configure load sharing on your MPLS VPN that uses BGP.

To load share traffic at the iBGP multipath level, it is recommended that you configure BGP labeling using the neighbor send-label command in router configuration mode. When you configure the iBGP multipath feature, the following message is displayed as a reminder to use the neighbor send-label command functionality: 

WARNING: Using iBGP multipath feature with LDP or TE based LSPs towards the BGP nexthop, paths taken by forwarding may not be as expected. Please consider configuring BGP labeling (RFC 3107) for proper forwarding behavior.

The following sections describe some BGP multipath options:

Internal BGP Multipath Load Sharing

When a BGP-speaking router with no local policy configured receives multiple network layer reachability information (NLRI) from the internal BGP (iBGP) for the same destination, the router chooses one iBGP path as the best path. The best path is then installed in the IP routing table of the router. The iBGP multipath feature enables the BGP-speaking router to select multiple iBGP paths as the best paths to a destination. The best paths are then installed in the IP routing table of the router. To enable iBGP multipath load sharing, you issue the maximum-paths ibgp command in router configuration mode. For more information about iBGP multipath load sharing, see Configuring BGP.

BGP Multipath for eBGP and iBGP

The BGP multipath load sharing for both eBGP and iBGP in an MPLS VPN feature allows multihomed autonomous systems and provider edge (PE) routers to be configured to distribute traffic across both external BGP (eBGP) and iBGP paths.

BGP installs up to the maximum number of paths allowed (configured using the maximum-paths command). BGP uses the best path algorithm to select one multipath as the best path, inserts the best path into the routing information base (RIB), and advertises the best path to BGP peers. Other multipaths can be inserted into the RIB, but only one path is selected as the best path.

Cisco Express Forwarding uses mutlipaths to perform load balancing on a per-packet or per-source or destination pair basis. To enable the load sharing feature, configure the router with MPLS VPNs that contain VPN routing and forwarding instances (VRFs) that import both eBGP and iBGP paths. You can configure the number of multipaths separately for each VRF.


Note
This feature operates within the configuration parameters of the existing outbound routing policy.
eBGP and iBGP Multipath Load Sharing in an MPLS Network Using BGP

The figure below shows an MPLS service provider network using BGP that connects two remote networks to PE1 and PE2, which are both configured for VPNv4 unicast iBGP peering. Network 2 is a multihomed network that is connected to PE1 and PE2. Network 2 also has extranet VPN services configured with Network 1. Both Network 1 and Network 2 are configured for eBGP peering with the PE routers.



You can configure PE1 so that both iBGP and eBGP paths can be selected as multipaths and imported into the VRF of Network 1. Cisco Express Forwarding uses the mutlipaths to perform load balancing. Traffic is distributed as follows:

  • IP traffic that is sent from Network 2 to PE1 and PE2 is sent across the eBGP paths as IP traffic.
  • IP traffic that is sent from PE1 to PE2 is sent across the iBGP path as MPLS traffic.
  • MPLS traffic that is sent across an eBGP path is sent as IP traffic.

Any prefix that is advertised from Network 2 will be received by PE1 through route distinguisher (RD) 21 and RD22.

  • The advertisement through RD21 is carried in IP packets.
  • The advertisement through RD22 is carried in MPLS packets.

Both paths can be selected as multipaths for VRF1 and inserted into the VRF1 RIB.

eBGP and iBGP Multipath Load Sharing with Route Reflectors

The figure below shows a topology that contains three PE routers and a route reflector, all configured for iBGP peering. PE2 and PE3 each advertise an equal preference eBGP path to PE1. By default, the route reflector chooses only one path and advertises PE1.



For all equal preference paths to PE1 to be advertised through the route reflector, you must configure each VRF with a different RD. The prefixes received by the route reflector are recognized differently and advertised to PE1.

eBGP Multipath Load Sharing

When a router learns two identical eBGP paths for a prefix from a neighboring autonomous system, it chooses the path with the lower route ID as the best path. This best path is installed in the IP routing table. You can enable eBGP multipath, which installs multiple paths in the IP routing table when the eBGP paths are learned from a neighboring autonomous system, instead of picking one best path.

During packet switching, depending on the switching mode, either per-packet or per-destination load sharing is performed among the multiple paths. The maximum-paths router configuration command controls the number of paths allowed. By default, BGP installs only one path to the IP routing table.

Load Sharing Using Directly Connected Loopback Peering

You use this feature with MPLS VPN Inter-AS and MPLS VPN carrier supporting carrier (CSC) networks to load share traffic between adjacent label switched routers (LSRs) that are connected by multiple links. The LSRs could be a pair of autonomous system boundary routers (ASBRs) or a CSC-PE and a CSC-CE.

Using directly connected loopback peering allows load sharing at the IGP level, so more than one BGP session is not needed between the LSRs. No other label distribution mechanism is needed between the adjacent LSRs than BGP.

Directly connected loopback peering enables load sharing of traffic as follows:

  • A BGP session is established, using the loopback addresses of the LSRs.
  • MPLS is enabled on the connecting links.
  • Multiple static routes to the loopback address of the adjacent LSR allow IGP load sharing.
  • The outgoing label to the loopback address of the adjacent LSR is an implicit null label and is inferred by the LSR.
  • Because IGP load sharing is enabled on the loopback address of the adjacent LSR, any traffic destined to a prefix that is learned over the BGP session (and recurses over the loopback) is load shared.

How to Configure Load Sharing

Configuring BGP Multipath Load Sharing for eBGP and iBGP

To configure iBGP and eBGP routes for multipath load sharing, perform the following task.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    router bgp as-number

4.    address-family ipv4 [multicast | unicast | vrf vrf-name]

5.    maximum-paths eibgp number-of-paths


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
router bgp as-number


Example:

Router(config)# router bgp 1

 

Enters router configuration mode and configures the router to run a BGP routing process.

 
Step 4
address-family ipv4 [multicast | unicast | vrf vrf-name]


Example:

Router(config-router)# address-family ipv4 vrf vrf1

 

Enters address family configuration mode for configuring routing sessions such as BGP that use standard IPv4 address prefixes.

Note    For this task you must create the VRF and specify the vrf keyword.
  • The multicast keyword specifies IPv4 multicast address prefixes.
  • The unicast keyword specifies IPv4 unicast address prefixes.
  • The vrf vrf-name keyword and argument specify the name of the VRF to associate with subsequent IPv4 address family configuration mode commands.
 
Step 5
maximum-paths eibgp number-of-paths


Example:

Router(config-router-af)# maximum-paths eibgp 6

 

Configures the number of parallel iBGP and eBGP routes that can be installed into a routing table.

 

Verifying BGP Multipath Load Sharing for eBGP and iBGP

To verify the configuration of iBGP and eBGP routes for multipath load sharing, perform this task.

SUMMARY STEPS

1.    enable

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


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

(Optional) Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
show ip bgp vpnv4 {all | rd route-distinguisher | vrf vrf-name} | [rib-failure] [ip-prefix/length [longer-prefixes]] [network-address [mask] [longer-prefixes]] [cidr-only] [community] [community-list] [dampened-paths] [filter-list] [flap-statistics] [inconsistent-as] [neighbors] [paths [line]] [peer-group] [quote-regexp] [regexp] [summary] [labels]


Example:

Router# show ip bgp vpnv4 all

 

Displays attributes and multipaths for a specific network in an MPLS VPN.

  • Enter one or more keywords or arguments.
 

Configuring eBGP Multipath Load Sharing with MPLS VPN Inter-AS

Perform this task on the ASBRs to configure eBGP Multipath for MPLS VPN interautonomous systems with ASBRs exchanging IPv4 routes and MPLS labels.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    router bgp as-number

4.    neighbor {ip-address | peer-group-name} remote-as as-number

5.    address-family ipv4 [multicast | unicast | vrf vrf-name]

6.    maximum-paths number-paths

7.    neighbor {ip-address | peer-group-name} activate

8.    neighbor ip-address send-label

9.    exit-address-family

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
router bgp as-number


Example:

Router(config)# router bgp 100

 

Configures a BGP routing process and places the router in router configuration mode.

  • The as-number argument indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along. Valid numbers are from 0 to 65535. Private autonomous system numbers that can be used in internal networks range from 64512 to 65535.
 
Step 4
neighbor {ip-address | peer-group-name} remote-as as-number


Example:

Router(config-router)# neighbor 10.0.0.1 remote-as 200

 

Adds an entry to the BGP or multiprotocol BGP neighbor table.

  • The ip-address argument specifies the IP address of the neighbor.
  • The peer-group-name argument specifies the name of a BGP peer group.
  • The as-number argument specifies the autonomous system to which the neighbor belongs.
 
Step 5
address-family ipv4 [multicast | unicast | vrf vrf-name]


Example:

Router(config-router)# address-family ipv4

 

Enters address family configuration mode for configuring routing sessions such as BGP that use standard IPv4 address prefixes.

  • The multicast keyword specifies IPv4 multicast address prefixes.
  • The unicast keyword specifies IPv4 unicast address prefixes.
  • The vrf vrf-name keyword and argument specify the name of the VRF to associate with subsequent IPv4 address family configuration mode commands.
 
Step 6
maximum-paths number-paths


Example:

Router(config-router-af)# maximum-paths 2

 

(Optional) Controls the maximum number of parallel routes an IP routing protocol can support.

  • The number-paths argument specifies the maximum number of parallel routes an IP routing protocol installs in a routing table.
 
Step 7
neighbor {ip-address | peer-group-name} activate


Example:

Router(config-router-af)# neighbor 10.0.0.1 activate

 

Enables the exchange of information with a neighboring router.

  • The ip-address argument specifies the IP address of the neighbor.
  • The peer-group-name argument specifies the name of a BGP peer group.
 
Step 8
neighbor ip-address send-label


Example:

Router(config-router-af)# neighbor 10.0.0.1 send-label

 

Enables a BGP router to send MPLS labels with BGP routes to a neighboring BGP router.

  • The ip-address argument specifies the IP address of the neighboring router.
 
Step 9
exit-address-family


Example:

Router(config-router-af)# exit-address-family

 

Exits address family configuration mode.

 
Step 10
end


Example:

Router(config-router-af)# end

 

(Optional) Exits to privileged EXEC mode.

 

Configuring eBGP Multipath Load Sharing with MPLS VPN Carrier Supporting Carrier on the CSC-PE Routers

Perform this task to configure eBGP Multipath load sharing on the CSC-PE routers that distribute BGP routes with MPLS labels.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    router bgp as-number

4.    address-family ipv4 [multicast | unicast | vrf vrf-name]

5.    maximum-paths number-paths

6.    neighbor {ip-address | peer-group-name} remote-as as-number

7.    neighbor {ip-address | peer-group-name} activate

8.    neighbor ip-address as-override

9.    neighbor ip-address send-label

10.    exit-address-family

11.    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
router bgp as-number


Example:

Router(config)# router bgp 100

 

Configures a BGP routing process and enters router configuration mode.

  • The as-number argument indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along. Valid numbers are from 0 to 65535. Private autonomous system numbers that can be used in internal networks range from 64512 to 65535.
 
Step 4
address-family ipv4 [multicast | unicast | vrf vrf-name]


Example:

Router(config-router)# address-family ipv4 vrf vpn1

 

Specifies the IPv4 address family type and enters address family configuration mode.

  • The multicast keyword specifies IPv4 multicast address prefixes.
  • The unicast keyword specifies IPv4 unicast address prefixes.
  • The vrf vrf-name keyword and argument specify the name of the VRF to associate with subsequent IPv4 address family configuration mode commands.
 
Step 5
maximum-paths number-paths


Example:

Router(config-router-af)# maximum-paths 2

 

(Optional) Controls the maximum number of parallel routes an IP routing protocol can support.

  • On the CSC-PE router, this command is enabled in address family configuration mode.
  • The number-paths argument specifies the maximum number of parallel routes an IP routing protocol installs in a routing table.
 
Step 6
neighbor {ip-address | peer-group-name} remote-as as-number


Example:

Router(config-router-af)# neighbor 10.0.0.1 remote-as 200

 

Adds an entry to the BGP or multiprotocol BGP neighbor table.

  • The ip-address argument specifies the IP address of the neighbor.
  • The peer-group-name argument specifies the name of a BGP peer group.
  • The as-number argument specifies the autonomous system to which the neighbor belongs.
 
Step 7
neighbor {ip-address | peer-group-name} activate


Example:

Router(config-router-af)# neighbor 10.0.0.1 activate

 

Enables the exchange of information with a neighboring BGP router.

  • The ip-address argument specifies the IP address of the neighbor.
  • The peer-group-name argument specifies the name of a BGP peer group.
 
Step 8
neighbor ip-address as-override


Example:

Router(config-router-af)# neighbor 10.0.0.1 as-override

 

Configures a PE router to override the autonomous system number (ASN) of a site with the ASN of a provider.

  • The ip-address argument specifies the IP address of the router that is to be overridden with the ASN provided.
 
Step 9
neighbor ip-address send-label


Example:

Router(config-router-af)# neighbor 10.0.0.1 send-label

 

Enables a BGP router to send MPLS labels with BGP routes to a neighboring BGP router.

  • The ip-address argument specifies the IP address of the neighboring router.
 
Step 10
exit-address-family


Example:

Router(config-router-af)# exit-address-family

 

Exits address family configuration mode.

 
Step 11
end


Example:

Router(config-router)# end

 

(Optional) Exits to privileged EXEC mode.

 

Configuring eBGP Multipath Load Sharing with MPLS VPN Carrier Supporting Carrier on the CSC-CE Routers

Perform this task to configure eBGP Multipath load sharing on the CSC-CE routers.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    router bgp as-number

4.    maximum-paths number-paths

5.    address-family ipv4 [multicast | unicast | vrf vrf-name]

6.    redistribute protocol

7.    neighbor {ip-address | peer-group-name} remote-as as-number

8.    neighbor {ip-address | peer-group-name} activate

9.    neighbor ip-address send-label

10.    exit-address-family

11.    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
router bgp as-number


Example:

Router(config)# router bgp 200

 

Configures a BGP routing process and enters router configuration mode.

  • The as-number argument indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along. Valid numbers are from 0 to 65535. Private autonomous system numbers that can be used in internal networks range from 64512 to 65535.
 
Step 4
maximum-paths number-paths


Example:

Router(config-router)# maximum-paths 2

 

(Optional) Controls the maximum number of parallel routes an IP routing protocol can support.

  • On the CSC-CE routers, this command is issued in router configuration mode.
  • The number-paths argument specifies the maximum number of parallel routes an IP routing protocol installs in a routing table.
 
Step 5
address-family ipv4 [multicast | unicast | vrf vrf-name]


Example:

Router(config-router)# address-family ipv4

 

Specifies the IPv4 address family type and enters address family configuration mode.

  • The multicast keyword specifies IPv4 multicast address prefixes.
  • The unicast keyword specifies IPv4 unicast address prefixes.
  • The vrf vrf-name keyword and argument specify the name of the VRF to associate with subsequent IPv4 address family configuration mode commands.
 
Step 6
redistribute protocol


Example:

Router(config-router-af)# redistribute static

 

Redistributes routes from one routing domain into another routing domain.

  • The protocol argument specifies the source protocol from which routes are being redistributed. It can be one of the following keywords: bgp, connected, egp, igrp, isis, mobile, ospf, rip, and static [ip].
    • The static [ip] keyword redistributes IP static routes.
Note    The optional ip keyword is used when you redistribute static routes into Intermediate System- to-Intermediate System (IS-IS).
    • The connected keyword refers to routes that are established automatically when IP is enabled on an interface.
    • For routing protocols such as Open Shortest Path First (OSPF) and IS-IS, these routes are redistributed as external to the autonomous system.
 
Step 7
neighbor {ip-address | peer-group-name} remote-as as-number


Example:

Router(config-router-af)# neighbor 10.0.0.2 remote-as 100

 

Adds an entry to the BGP or multiprotocol BGP neighbor table.

  • The ip-address argument specifies the IP address of the neighbor.
  • The peer-group-name argument specifies the name of a BGP peer group.
  • The as-number argument specifies the autonomous system to which the neighbor belongs.
 
Step 8
neighbor {ip-address | peer-group-name} activate


Example:

Router(config-router-af)# neighbor 10.0.0.2 activate

 

Enables the exchange of information with a neighboring BGP router.

  • The ip-address argument specifies the IP address of the neighbor.
  • The peer-group-name argument specifies the name of a BGP peer group.
 
Step 9
neighbor ip-address send-label


Example:

Router(config-router-af)# neighbor 10.0.0.2 send-label

 

Enables a BGP router to send MPLS labels with BGP routes to a neighboring BGP router.

  • The ip-address argument specifies the IP address of the neighboring router.
 
Step 10
exit-address-family


Example:

Router(config-router-af)# exit-address-family

 

Exits address family configuration mode.

 
Step 11
end


Example:

Router(config-router)# end

 

(Optional) Exits to privileged EXEC mode.

 

Configuring DCLP for MPLS VPN Inter-AS using ASBRs to Exchange VPN-IPv4 Addresses

This section describes the following tasks you need to do to configure peering of loopback interfaces of directly connected ASBRs:

The figure below shows the loopback configuration for directly connected ASBR1 and ASBR2. This configuration is used as the example in the tasks that follow.

Figure 1 Loopback Interface Configuration for Directly Connected ASBR1 and ASBR2


Configuring Loopback Interface Addresses for Directly Connected ASBRs

Perform this task to configure loopback interface addresses for directly connected ASBRs.


Note
Loopback addresses need to be configured for each directly connected ASBR. That is, configure a loopback address for ASBR1 and for ASBR2 in the example shown in the figure above.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface loopback interface- number

4.    ip address ip-address mask [secondary]

5.    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
interface loopback interface- number


Example:

Router(config)# interface loopback 0

 

Configures a software-only virtual interface that emulates an interface that is always up and enters interface configuration mode.

  • The interface-number argument is the number of the loopback interface that you want to create or configure. There is no limit on the number of loopback interfaces that you can create.
 
Step 4
ip address ip-address mask [secondary]


Example:

Router(config-if)# ip address 10.10.10.10 255.255.255.255

 

Sets a primary or secondary IP address for an interface.

  • The ip-address argument is the IP address.
  • The mask argument is the mask for the associated IP subnet.
  • The secondary keyword specifies that the configured address is a secondary IP address. If this keyword is omitted, the configured address is the primary IP address.
 
Step 5
end


Example:

Router(config-if)# end

 

Exits to privileged EXEC mode.

 

Configuring 32 Static Routes to the eBGP Neighbor Loopback

Perform this task to configure /32 static routes to the eBGP neighbor loopback.


Note
You need to configure /32 static routes on each of the directly connected ASBRs.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]

4.    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
ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]


Example:

Router(config)# ip route 10.20.20.20 255.255.255.255 Ethernet 1/0 172.16.0.1

 

Establishes static routes.

  • The prefix argument is the IP route prefix for the destination.
  • The mask argument is the prefix mask for the destination.
  • The ip-address argument is the IP address of the next hop that you can use to reach the specified network.
  • The interface-type and interface-number arguments are the network interface type and interface number.
  • The distance argument is an administrative distance.
  • The name argument applies a name to the specified route.
  • The permanent keyword specifies that the route is not to be removed, even if the interface shuts down.
  • The tag tag keyword and argument name a tag value that can be used as a "match" value for controlling redistribution through the use of route maps.
 
Step 4
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring Forwarding on Connecting Loopback Interfaces

Perform this task to configure forwarding on the connecting loopback interfaces.

This task is required for sessions between loopbacks. In the Configuring 32 Static Routes to the eBGP Neighbor Loopback task, Ethernet 1/0 and Ethernet 0/0 are the connecting interfaces.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type slot/port

4.    mpls bgp forwarding

5.    exit

6.    Repeat Steps 3 and 4 for another connecting interface (Ethernet 0/0).

7.    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
interface type slot/port


Example:

Router(config)# interface ethernet 1/0

 

Configures an interface type and enters interface configuration mode.

  • The type argument is the type of interface to be configured.
  • The slot argument is the slot number. Refer to the appropriate hardware manual for slot and port information.
  • The /port argument is the port number. Refer to the appropriate hardware manual for slot and port information.
 
Step 4
mpls bgp forwarding


Example:

Router(config-if)# mpls bgp forwarding

 

Configures BGP to enable MPLS forwarding on connecting interfaces.

 
Step 5
exit


Example:

Router(config-if)# exit

 

Exits to global configuration mode.

 
Step 6
Repeat Steps 3 and 4 for another connecting interface (Ethernet 0/0).  
 
Step 7
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring an eBGP Session Between the Loopbacks

Perform this task to configure an eBGP session between the loopbacks.


Note
You need to configure an eBGP session between loopbacks on each directly connected ASBR.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    router bgp as-number

4.    no bgp default route-target filter

5.    neighbor {ip-address | peer-group-name} remote-as as-number

6.    neighbor {ip-address | peer-group-name} disable-connected-check

7.    neighbor {ip-address | ipv6-address | peer-group-name} update-source interface-type interface-number

8.    address-family vpnv4 [unicast]

9.    neighbor {ip-address | peer-group-name | ipv6-address} activate

10.    neighbor {ip-address | peer-group-name} send-community [both | standard extended]

11.    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
router bgp as-number


Example:

Router(config)# router bgp 200

 

Configures the BGP routing process.

  • The as-number indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along.
 
Step 4
no bgp default route-target filter


Example:

Router(config)# no bgp default route-target filter

 

Disables BGP route-target filtering, and enters router configuration mode.

  • All received BGP VPN-IPv4 routes are accepted by the router.
 
Step 5
neighbor {ip-address | peer-group-name} remote-as as-number


Example:

Router(config-router)# neighbor 10.20.20.20 remote-as 100

 

Adds an entry to the BGP or multiprotocol BGP neighbor table.

  • The ip-address argument is the IP address of the neighbor.
  • The peer-group-name argument is the name of a BGP peer group.
  • The as-number argument is the autonomous system to which the neighbor belongs.
 
Step 6
neighbor {ip-address | peer-group-name} disable-connected-check


Example:

Router(config-router)# neighbor 10.20.20.20 disable-connected-check

 

Allows peering between loopbacks.

  • The ip-address argument is the IP address of the neighbor.
  • The peer-group-name argument is the name of a BGP peer group.
 
Step 7
neighbor {ip-address | ipv6-address | peer-group-name} update-source interface-type interface-number


Example:

Router(config-router)# neighbor 10.20.20.20 update-source Loopback 0

 

Allows BGP sessions to use any operational interface for TCP connections.

  • The ip-address argument is the IPv4 address of the BGP-speaking neighbor.
  • The ipv6-address argument is the IPv6 address of the BGP-speaking neighbor.

This argument must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.

  • The peer-group-name argument is the name of a BGP peer group.
  • The interface-type argument is the interface type.
  • The interface-number argument is the interface number.
 
Step 8
address-family vpnv4 [unicast]


Example:

Router(config-router)# address-family vpnv4

 

Enters address family configuration mode for configuring routing protocols such as BGP, Routing Information Protocol (RIP), and static routing.

  • The unicast keyword specifies unicast prefixes.
 
Step 9
neighbor {ip-address | peer-group-name | ipv6-address} activate


Example:

Router(config-router-af)# neighbor 10.20.20.20 activate

 

Enables the exchange of information with a BGP neighbor.

  • The ip-address argument is the IP address of the neighboring router.
  • The peer-group-name argument is the name of a BGP peer group.
  • The ipv6-address argument is the IPv6 address of the BGP-speaking neighbor.
Note    This argument must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.
 
Step 10
neighbor {ip-address | peer-group-name} send-community [both | standard extended]


Example:

Router(config-router-af)# neighbor 10.20.20.20 send-community extended

 

Specifies that a communities attribute should be sent to a BGP neighbor.

  • The ip-address argument is the IP address of the neighboring router.
  • The peer-group-name argument is the name of a BGP peer group.
  • The both keyword specifies that both standard and extended communities will be sent.
  • The standard keyword specifies that only standard communities will be sent.
  • The extended keyword specifies that only extended communities will be sent.
 
Step 11
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Verifying That Load Sharing Occurs Between Loopbacks

Perform this task to verify that load sharing occurs between loopbacks. You need to ensure that the MPLS Label Forwarding Information Base (LFIB) entry for the neighbor route lists the available paths and interfaces.

SUMMARY STEPS

1.    enable

2.    show mpls forwarding-table {mask | length} | labels label [network label] | interface interface | next-hop address | lsp-tunnel [tunnel-id]] [vrf vrf-name] [detail]

3.    disable


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

(Optional) Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
show mpls forwarding-table {mask | length} | labels label [network label] | interface interface | next-hop address | lsp-tunnel [tunnel-id]] [vrf vrf-name] [detail]


Example:

Router# show mpls forwarding-table

 

Displays the contents of the MPLS LFIB.

  • Enter an optional keyword or argument if desired.
 
Step 3
disable


Example:

Router# disable

 

Exits to user EXEC mode.

 

Configuring DCLP for MPLS VPN Inter-AS Using ASBRs to Exchange IPv4 Routes and Labels

The following sections describe how to configure peering of loopback interfaces of directly connected ASBRs to achieve load sharing in an interautonomous system network:

The figure below shows the loopback configuration for directly connected ASBR1 and ASBR2. This configuration is used as the example in the tasks that follow.

Figure 2 Loopback Interface Configuration for Directly Connected ASBR1 and ASBR2


Configuring Loopback Interface Addresses for Directly Connected ASBRs

Perform this task to configure loopback interface addresses.


Note
Loopback addresses need to be configured for each directly connected ASBR. That is, configure a loopback address for ASBR1 and for ASBR2 as in the example shown in the figure above.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface loopback interface number

4.    ip address ip-address [mask [secondary]]

5.    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
interface loopback interface number


Example:

Router(config)# interface loopback 0

 

Configures a software-only virtual interface that emulates an interface that is always up and enters interface configuration mode.

  • The interface-number argument is the number of the loopback interface that you want to create or configure. There is no limit on the number of loopback interfaces that you can create.
 
Step 4
ip address ip-address [mask [secondary]]


Example:

Router(config-if)# ip address 10.10.10.10 255.255.255.255

 

Sets a primary or secondary IP address for an interface.

  • The ip-address argument is the IP address.
  • The mask argument is the mask for the associated IP subnet.
  • The secondary keyword specifies that the configured address is a secondary IP address. If this keyword is omitted, the configured address is the primary IP address.
 
Step 5
end


Example:

Router(config-if)# end

 

Exits to privileged EXEC mode.

 

Configuring 32 Static Routes to the eBGP Neighbor Loopback

Perform this task to configure /32 static routes to the eBGP neighbor loopback.


Note
You need to configure /32 static routes on each of the directly connected ASBRs.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]

4.    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
ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]


Example:

Router(config)# ip route 10.20.20.20 255.255.255.255 Ethernet 1/0 172.16.0.1

 

Establishes static routes.

  • The prefix argument is the IP route prefix for the destination.
  • The mask argument is the prefix mask for the destination.
  • The ip-address argument is the IP address of the next hop that you can use to reach the specified network.
  • The interface-type and interface-number arguments are the network interface type and interface number.
  • The distance argument is an administrative distance.
  • The name argument applies a name to the specified route.
  • The permanent keyword specifies that the route is not to be removed, even if the interface shuts down.
  • The tag tag keyword and argument name a tag value that can be used as a "match" value for controlling redistribution through the use of route maps.
 
Step 4
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring Forwarding on Connecting Loopback Interfaces

Perform this task to configure forwarding on the connecting loopback interfaces.

This task is required for sessions between loopbacks. In the Configuring 32 Static Routes to the eBGP Neighbor Loopback task, Ethernet1/0 and Ethernet0/0 are the connecting interfaces.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type slot/port

4.    mpls bgp forwarding

5.    exit

6.    Repeat Steps 3 and 4 for another connecting interface (Ethernet 0/0).

7.    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
interface type slot/port


Example:

Router(config)# interface ethernet 1/0

 

Configures an interface type and enters interface configuration mode.

  • The type argument is the type of interface to be configured.
  • The slot argument is the slot number. Refer to the appropriate hardware manual for slot and port information.
  • The /port argument is the port number. Refer to the appropriate hardware manual for slot and port information.
 
Step 4
mpls bgp forwarding


Example:

Router(config-if)# mpls bgp forwarding

 

Configures BGP to enable MPLS forwarding on connecting interfaces.

 
Step 5
exit


Example:

Router(config-if)# exit

 

Exits to global configuration mode.

 
Step 6
Repeat Steps 3 and 4 for another connecting interface (Ethernet 0/0).  
 
Step 7
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring an eBGP Session Between the Loopbacks

Perform the following tasks to configure an eBGP session between the loopbacks.


Note
You need to configure an eBGP session between loopbacks on each directly connected ASBR.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    router bgp as-number

4.    bgp log-neighbor-changes

5.    neighbor {ip-address | peer-group-name} remote-as as-number

6.    neighbor {ip-address | peer-group-name} disable-connected-check

7.    neighbor {ip-address | ipv6-address | peer-group-name} update-source interface-type interface-number

8.    address-family ipv4 [unicast] vrf vrf-name

9.    neighbor {ip-address | peer-group-name | ipv6-address} activate

10.    neighbor {ip-address | peer-group-name} send-community [both | standard | extended

11.    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
router bgp as-number


Example:

Router(config)# router bgp 200

 

Configures the BGP routing process, and enters router configuration mode.

  • The as-number argument indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along.
 
Step 4
bgp log-neighbor-changes


Example:

Router(config-router)# bgp log-neighbor-changes

 

Enables logging of BGP neighbor resets.

 
Step 5
neighbor {ip-address | peer-group-name} remote-as as-number


Example:

Router(config-router)# neighbor 10.20.20.20 remote-as 100

 

Adds an entry to the BGP or multiprotocol BGP neighbor table.

  • The ip-address argument is the IP address of the neighbor.
  • The peer-group-name argument is the name of a BGP peer group.
  • The as-number argument is the number of the autonomous system to which the neighbor belongs.
 
Step 6
neighbor {ip-address | peer-group-name} disable-connected-check


Example:

Router(config-router)# neighbor 10.20.20.20 disable-connected-check

 

Allows peering between loopbacks.

  • The ip-address argument is the IP address of the neighbor.
  • The peer-group-name argument is the name of a BGP peer group.
 
Step 7
neighbor {ip-address | ipv6-address | peer-group-name} update-source interface-type interface-number


Example:

Router(config-router)# neighbor 10.20.20.20 update-source Loopback 0

 

Allows BGP sessions to use any operational interface for TCP connections.

  • The ip-address argument is the IPv4 address of the BGP-speaking neighbor.
  • The ipv6-address argument is the IPv6 address of the BGP-speaking neighbor.
Note    This argument must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.
  • The peer-group-name argument is the name of a BGP peer group.
  • The interface-type argument is the interface type.
  • The interface-number argument is the interface number.
 
Step 8
address-family ipv4 [unicast] vrf vrf-name


Example:

Router(config-router)# address-family ipv4

 

Enters address family configuration mode for configuring routing protocols such as BGP, Routing Information Protocol (RIP), and static routing.

  • The unicast keyword specifies unicast prefixes.
  • The vrf vrf-name keyword and argument specify the name of a VPN routing/forwarding instance (VRF) to associate with submode commands.
 
Step 9
neighbor {ip-address | peer-group-name | ipv6-address} activate


Example:

Router(config-router-af)# neighbor 10.20.20.20 activate

 

Enables the exchange of information with a BGP neighbor.

  • The ip-address argument is the IP address of the neighboring router.
  • The peer-group-name argument is the name of the BGP peer group.
  • The ipv6-address argument is the IPv6 address of the BGP-speaking neighbor.
Note    This argument must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.
 
Step 10
neighbor {ip-address | peer-group-name} send-community [both | standard | extended


Example:

Router(config-router-af)# neighbor 10.20.20.20 send-community extended

 

Specifies that a communities attribute should be sent to a BGP neighbor.

  • The ip-address argument is the IP address of the neighboring router.
  • The peer-group-name argument is the name of the BGP peer group.
  • The both keyword specifies that both standard and extended communities will be sent.
  • The standard keyword specifies that only standard communities will be sent.
  • The extended keyword specifies that only extended communities will be sent.
 
Step 11
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Verifying That Load Sharing Occurs Between Loopbacks

To verify that load sharing can occur between loopbacks, ensure that the MPLS LFIB entry for the neighbor route lists the available paths and interfaces.

SUMMARY STEPS

1.    enable

2.    show mpls forwarding-table [network {mask |length} | labels label [label] | interface interface | next-hop address | lsp-tunnel [tunnel-id]] [vrf vrf-name] [detail]

3.    disable


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
show mpls forwarding-table [network {mask |length} | labels label [label] | interface interface | next-hop address | lsp-tunnel [tunnel-id]] [vrf vrf-name] [detail]


Example:

Router# show mpls forwarding-table

 

Displays the contents of the MPLS LFIB.

  • Enter a keyword or argument, if desired.
 
Step 3
disable


Example:

Router# disable

 

Exits to user EXEC mode.

 

Configuring Directly Connected Loopback Peering on MPLS VPN Carrier Supporting Carrier

The following sections explain how to load balance CSC traffic by peering loopback interfaces of directly connected CSC-PE and CSC-CE routers:

The figure below shows the loopback configuration for directly connected CSC-PE and CSC-CE routers. This configuration is used as the example in the tasks that follow.

Figure 3 Loopback Interface Configuration for Directly Connected CSC-PE and CSC-CE Routers


Configuring Loopback Interface Addresses on CSC-PE Routers

Perform this task to configure loopback interface addresses on the CSC-PE router.


Note
Configuration of a loopback interface address on the CSC-PE router requires the enabling of a VRF. The CSC-CE router loopback interface does not require the enabling a of VRF.
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface loopback interface number

4.    ip vrf forwarding vrf-name

5.    ip addres ip-address mask [secondary]

6.    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
interface loopback interface number


Example:

Router(config)# interface loopback 0

 

Configures a software-only virtual interface that emulates an interface that is always up, and enters interface configuration mode.

  • The interface-number argument is the number of the loopback interface that you want to create or configure. There is no limit on the number of loopback interfaces that you can create.
 
Step 4
ip vrf forwarding vrf-name


Example:

Router(config-if)# ip vrf forwarding vpn1

 

Associates a VRF with the specified interface or subinterface.

  • The vrf-name argument is the name assigned to a VRF.
 
Step 5
ip addres ip-address mask [secondary]


Example:

Router(config-if)# ip address 10.20.20.20 255.255.255.255

 

Sets a primary or secondary IP address for an interface.

  • The ip-address argument is the IP address.
  • The mask argument is the mask for the associated IP subnet.
  • The secondary keyword specifies that the configured address is a secondary IP address. If this keyword is omitted, the configured address is the primary IP address.
 
Step 6
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring Loopback Interface Addresses for CSC-CE Routers

Perform this task to configure loopback interface addresses for CSC-CE routers.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface loopback interface-number

4.    ip address ip-address mask [secondary]

5.    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
interface loopback interface-number


Example:

Router(config)# interface loopback 0

 

Configures a software-only virtual interface that emulates an interface that is always up.

  • The interface-number argument is the number of the loopback interface that you want to create or configure. There is no limit on the number of loopback interfaces that you can create.
 
Step 4
ip address ip-address mask [secondary]


Example:

Router(config-if)# ip address 10.10.10.10 255.255.255.255

 

Sets a primary or secondary IP address for an interface.

  • The ip-address argument is the IP address.
  • The mask argument is the mask for the associated IP subnet.
  • The secondary keyword specifies that the configured address is a secondary IP address. If this keyword is omitted, the configured address is the primary IP address.
 
Step 5
end


Example:

Router(config-if)# end

 

Exits to privileged EXEC mode.

 

Configuring 32 Static Routes to the eBGP Neighbor Loopback on the CSC-PE Router

Perform the following task to configure /32 static routes to the eBGP neighbor loopback on the CSC-PE router.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip route vrf vrf-name prefix mask {ip-address | interface-type interface-number [ip-address]} [global] [distance] [name] [permanent] [tag tag]

4.    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
ip route vrf vrf-name prefix mask {ip-address | interface-type interface-number [ip-address]} [global] [distance] [name] [permanent] [tag tag]


Example:

Router(config)# ip route vrf vpn1 10.10.10.10 255.255.255.255 Ethernet 1/0 172.16.0.2

 

Establishes static routes for a VRF.

  • The vrf-name argument is the name of the VRF for the static route.
  • The prefix argument is the IP route prefix for the destination.
  • The mask argument is the prefix mask for the destination.
  • The ip-address argument is the IP address of the next hop that you can use to reach the destination network.
  • The interface-type and interface-number arguments are the network interface type and interface number.
  • The global keyword specifies that the given next hop address is in the nonVRF routing table.
  • The distance argument is an administrative distance.
  • The name argument applies a name to the specified route.
  • The permanent keyword specifies that the route is not to be removed, even if the interface shuts down.
  • The tag tag keyword and argument name a tag value that can be used as a "match" value for controlling redistribution via route maps.
 
Step 4
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring 32 Static Routes to the eBGP Neighbor Loopback on the CSC-CE Router

Perform the following task to configure /32 static routes to the eBGP neighbor loopback for the CSC-CE router.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]

4.    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
ip route prefix mask {ip-address | interface-type interface-number [ip-address]} [distance] [name] [permanent] [tag tag]


Example:

Router(config)# ip route 10.20.20.20 255.255.255.255 Ethernet 1/0 172.16.0.1

 

Establishes static routes.

  • The prefix argument is the IP route prefix for the destination.
  • The mask argument is the prefix mask for the destination.
  • The ip-address argument is the IP address of the next hop that you can use to reach the destination network.
  • The interface-type and interface-number arguments are the network interface type and interface number.
  • The distance argument is an administrative distance.
  • The name argument applies a name to the specified route.
  • The permanent keyword specifies that the route is not to be removed, even if the interface shuts down.
  • The tag tag keyword and argument name a tag value that can be used as a "match" value for controlling redistribution via route maps.
 
Step 4
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring Forwarding on CSC-PE Interfaces That Connect to the CSC-CE Loopback

Perform this task to configure forwarding on CSC-PE interfaces that connect to the CSC-CE loopback.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface type slot/port

4.    ip vrf forwarding vrf-name

5.    ip address ip-address mask [secondary]

6.    mpls bgp forwarding

7.    exit

8.    Repeat Steps 3 through 6 for another connecting interface (Ethernet 0/0).

9.    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
interface type slot/port


Example:

Router(config)# interface ethernet 1/0

 

Configures an interface type and enters interface configuration mode.

  • The type argument is the type of interface to be configured.
  • The slot argument is the slot number. Refer to the appropriate hardware manual for slot and port information.
  • The /port argument is the port number. Refer to the appropriate hardware manual for slot and port information.
 
Step 4
ip vrf forwarding vrf-name


Example:

Router(config-if)# ip vrf forwarding vpn1

 

Associates a VRF with an interface or subinterface.

  • The vrf-name argument is the name assigned to a VRF.
 
Step 5
ip address ip-address mask [secondary]


Example:

Router(config-if)# ip address 172.16.0.1 255.255.255.255

 

Sets a primary or secondary IP address for an interface.

  • The ip-address argument is the IP address.
  • The mask argument is the mask for the associated IP subnet.
  • The secondary keyword specifies that the configured address is a secondary IP address. If this keyword is omitted, the configured address is the primary IP address.
 
Step 6
mpls bgp forwarding


Example:

Router(config-if)# mpls bgp forwarding

 

Configures BGP to enable MPLS forwarding on connecting interfaces.

 
Step 7
exit


Example:

Router(config-if)# exit

 

Exits to global configuration mode.

 
Step 8
Repeat Steps 3 through 6 for another connecting interface (Ethernet 0/0).  
 
Step 9
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring Forwarding on CSC-CE Interfaces That Connect to the CSC-PE Loopback

Perform this task to configure forwarding on CSC-CE interfaces that connect to the CSC-PE loopback.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface typeslot/port

4.    mpls bgp forwarding

5.    exit

6.    Repeat Steps 3 and 4 for another connecting interface (Ethernet 0/0).

7.    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
interface typeslot/port


Example:

Router(config)# interface ethernet 1/0

 

Configures an interface type and enters interface configuration mode.

  • The type argument is the type of interface to be configured.
  • The slot argument is the slot number. Refer to the appropriate hardware manual for slot and port information.
  • The /port argument is the port number. Refer to the appropriate hardware manual for slot and port information.
 
Step 4
mpls bgp forwarding


Example:

Router(config-if)# mpls bgp forwarding

 

Configures BGP to enable MPLS forwarding on connecting interfaces.

 
Step 5
exit


Example:

Router(config-if)# exit

 

Exits to global configuration mode.

 
Step 6
Repeat Steps 3 and 4 for another connecting interface (Ethernet 0/0).  
 
Step 7
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring an eBGP Session Between the CSC-PE Router and the CSC-CE Loopback

Perform this task to configure an eBGP session between the CSC-PE router and the CSC-CE loopback.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    router bgp as-number

4.    bgp log-neighbor-changes

5.    neighbor {ip-address | peer-group-name} remote-as as-number

6.    neighbor {ip-address | peer-group-name} disable-connected-check

7.    neighbor {ip-address | ipv6-address | peer-group-name} update-source interface-type interface-number

8.    address-family ipv4 [unicast] vrf vrf-name

9.    ip vrf forwarding vrf-name

10.    neighbor {ip-address | peer-group-name | ipv6-address} activate

11.    neighbor ip-address send-label

12.    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
router bgp as-number


Example:

Router(config)# router bgp 200

 

Configures the BGP routing process.

  • The as-number argument indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along.
 
Step 4
bgp log-neighbor-changes


Example:

Router(config-router)# bgp log-neighbor-changes

 

Enables logging of BGP neighbor resets.

 
Step 5
neighbor {ip-address | peer-group-name} remote-as as-number


Example:

Router(config-router)# neighbor 10.10.10.10 remote-as 100

 

Adds an entry to the BGP or multiprotocol BGP neighbor table.

  • The ip-address argument is the IP address of the neighbor.
  • The peer-group-name argument is the name of a BGP peer group.
  • The as-number argument is the autonomous system to which the neighbor belongs.
 
Step 6
neighbor {ip-address | peer-group-name} disable-connected-check


Example:

Router(config-router)# neighbor 10.10.10.10 disable-connected-check

 

Allows peering between loopbacks.

  • The ip-addressargument is the IP address of the neighbor.
  • The peer-group-name argument is the name of a BGP peer group.
 
Step 7
neighbor {ip-address | ipv6-address | peer-group-name} update-source interface-type interface-number


Example:

Router(config-router)# neighbor 10.10.10.10 update-source Loopback 0

 

Allows BGP sessions to use any operational interface for TCP connections.

  • The ip-address argument is the IPv4 address of the BGP-speaking neighbor.
  • The ipv6-address argument is the IPv6 address of the BGP-speaking neighbor.

This argument must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.

  • The peer-group-name argument is the name of a BGP peer group.
  • The interface-type argument is the interface type.
  • The interface-number argument is the interface number.
 
Step 8
address-family ipv4 [unicast] vrf vrf-name


Example:

Router(config-router)# address-family ipv4 vrf vpn1

 

Enters address family configuration mode for configuring routing protocols such as BGP, Routing Information Protocol (RIP), and static routing.

  • The ipv4 keyword configures sessions that carry standard IPv4 address prefixes.
  • The unicast keyword specifies unicast prefixes.
  • The vrf vrf-name keyword and argument specify the name of a VRF to associate with submode commands.
 
Step 9
ip vrf forwarding vrf-name


Example:

Router(config-router-af)# ip vrf forwarding vpn1

 

Associates a VRF with an interface or subinterface.

  • The vrf-name argument is the name assigned to a VRF.
 
Step 10
neighbor {ip-address | peer-group-name | ipv6-address} activate


Example:

Router(config-router-af)# neighbor 10.10.10.10 activate

 

Enables the exchange of information with a BGP neighbor.

  • The ip-address argument is the IP address of the neighboring router.
  • The peer-group-name argument is the name of the BGP peer group.
  • The ipv6-address argument is the IPv6 address of the BGP-speaking neighbor.
Note    This argument must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.
 
Step 11
neighbor ip-address send-label


Example:

Router(config-router-af)# neighbor 10.10.10.10 send-label

 

Enables a BGP router to send MPLS labels with BGP routes to a neighboring BGP router.

  • The ip-addressargument is the IP address of the neighboring router.
 
Step 12
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Configuring an eBGP Session Between the CSC-CE Router and the CSC-PE Loopback

Perform this task to configure an eBGP session between the CSC-CE router and the CSC-PE loopback.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    router bgp as-number

4.    bgp log-neighbor-changes

5.    neighbor {ip-address | peer-group-name} remote-as as-number

6.    neighbor {ip-address | peer-group-name} disable-connected-check

7.    neighbor {ip-address | ipv6-address | peer-group-name} update-source interface-type interface-number

8.    address-family ipv4 [unicast] [vrf vrf-name]

9.    neighbor {ip-address | peer-group-name|ipv6-address] activate

10.    neighbor ip-address send-label

11.    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
router bgp as-number


Example:

Router(config)# router bgp 200

 

Configures the BGP routing process.

  • The as-number argument indicates the number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along.
 
Step 4
bgp log-neighbor-changes


Example:

Router(config-router)# bgp log-neighbor-changes

 

Enables logging of BGP neighbor resets.

 
Step 5
neighbor {ip-address | peer-group-name} remote-as as-number


Example:

Router(config-router)# neighbor 10.20.20.20 remote-as 100

 

Adds an entry to the BGP or multiprotocol BGP neighbor table.

  • The ip-address argument is the IP address of the neighbor.
  • The peer-group-name argument is the name of a BGP peer group.
  • The as-number argument is the autonomous system to which the neighbor belongs.
 
Step 6
neighbor {ip-address | peer-group-name} disable-connected-check


Example:

Router(config-router)# neighbor 10.20.20.20 disable-connected-check

 

Allows peering between loopbacks.

  • The ip-address argument is the IP address of the neighbor.
  • The peer-group-name argument is the name of a BGP peer group.
 
Step 7
neighbor {ip-address | ipv6-address | peer-group-name} update-source interface-type interface-number


Example:

Router(config-router)# neighbor 10.20.20.20 update-source Loopback 0

 

Allows BGP sessions to use any operational interface for TCP connections.

  • The ip-address argument is the IPv4 address of the BGP-speaking neighbor.
  • The ipv6-address argument is the IPv6 address of the BGP-speaking neighbor.

This argument must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.

  • The peer-group-name argument is the name of a BGP peer group.
  • The interface-type argument is the interface type.
  • The interface-number argument is the interface number.
 
Step 8
address-family ipv4 [unicast] [vrf vrf-name]


Example:

Router(config-router)# address-family ipv4

 

Enters address family configuration mode for configuring routing protocols such as BGP, RIP, and static routing.

  • The ipv4 keyword configures sessions that carry standard IPv4 address prefixes.
  • The unicast keyword specifies unicast prefixes.
  • The vrf vrf-name keyword and argument specify the name of a VRF to associate with submode commands.
 
Step 9
neighbor {ip-address | peer-group-name|ipv6-address] activate


Example:

Router(config-router-af)# neighbor 10.20.20.20 activate

 

Enables the exchange of information with a BGP neighbor.

  • The ip-address argument is the IP address of the neighboring router.
  • The peer-group-name argument is the name of the BGP peer group.
  • The ipv6-address argument is the IPv6 address of the BGP-speaking neighbor.
Note    This argument must be in the form documented in RFC 2373, where the address is specified in hexadecimal using 16-bit values between colons.
 
Step 10
neighbor ip-address send-label


Example:

Router(config-router-af)# neighbor 10.20.20.20 send-label

 

Enables a BGP router to send MPLS labels with BGP routes to a neighboring BGP router.

  • The ip-address argument is the IP address of the neighboring router.
 
Step 11
end


Example:

Router(config)# end

 

Exits to privileged EXEC mode.

 

Verifying That Load Sharing Occurs Between Loopbacks

To verify that load sharing occurs between loopbacks, ensure that the MPLS LFIB entry for the neighbor route lists the available paths and interfaces.

SUMMARY STEPS

1.    enable

2.    show mpls forwarding-table [vrf vrf-name] [{network {mask | length} | labels label [-label] | [ interface] interface | next-hop address | lsp-tunnel [tunnel-id]}] [detail]

3.    disable


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
show mpls forwarding-table [vrf vrf-name] [{network {mask | length} | labels label [-label] | [ interface] interface | next-hop address | lsp-tunnel [tunnel-id]}] [detail]


Example:

Router# show mpls forwarding-table

 

Displays the contents of the MPLS LFIB.

 
Step 3
disable


Example:

Router# disable

 

Exits to user EXEC mode.

 

Configuration Examples for Load Sharing MPLS VPN Traffic

Configuring a Router to Select eBGP or iBGP Paths as Multipaths Example

The following example configures a router in address family configuration mode to select six eBGP or iBGP paths as multipaths:

Router(config)# router bgp 100
Router(config-router)# address-family ipv4 vrf try
Router(config-router-af)# maximum-paths eibgp 6
Router(config-router-af)# end

Configuring a 32 Static Route from an ASBR to the Loopback Address of Another ASBR Examples

The following example configures a /32 static route from ASBR1 to the loopback address of ASBR2: 

Router# configure terminal
Router(config)# ip route 10.20.20.20 255.255.255 e1/0 168.192.0.1
Router(config)# ip route 10.20.20.20 255.255.255 e0/0 168.192.2.1

The following example configures a /32 static route from ASBR2 to the loopback address of ASBR1: 

Router# configure terminal
Router(config)# ip route vrf vpn1 10.10.10.10 255.255.255 e1/0 168.192.0.2
Router(config)# ip route vrf vpn1 10.10.10.10 255.255.255 e0/0 168.192.2.2

Configuring BGP MPLS Forwarding on the Interfaces Connecting ASBRs Example

The following example configures BGP/MPLS forwarding on the interfaces connecting ASBR2 with ASBR1:

Router# configure terminal
Router(config)# interface ethernet 1/0
Router(config-if)# ip vrf forwarding vpn1
Router(config-if)# ip address 168.192.0.1 255.255.255.255
Router(config-if)# mpls bgp forwarding
Router(config-if)# exit
Router(config)# interface ethernet 0/0
Router(config-if)# ip vrf forwarding vpn1
Router(config-if)# ip address 168.192.2.1 255.255.255.255
Router(config-if)# mpls bgp forwarding
Router(config-if)# exit

Configuring VPNv4 Sessions on an ASBR Example

The following example configures VPNv4 sessions on ASBR2:

Router# configure terminal
Router(config)# router bgp 200
Router(config-router)# bgp log-neighbor-changes
Router(config-router)# neighbor 10.10.10.10 remote-as 100
Router(config-router)# neighbor 10.10.10.10 disable-connected-check
Router(config-router)# neighbor 10.10.10.10 update-source Loopback0
!
Router(config-router)# address-family vpnv4
Router(config-router-af)# neighbor 10.10.10.10 activate
Router(config-router-af)# neighbor 10.10.10.10 send-community extended
Router(config-router-af)# end

Verifying VPN NLRI for a Specified Network Example

If you enter the all keyword with the show ip bgp vpnv4 command, the output displays information about all VPN network layer reachability information (NLRI) for a specified network: 

Router# show ip bgp vpnv4 all 10.22.22.0
BGP routing table entry for 10:1:22.22.22.0/24, version 19
Paths:(5 available, best #5)
Multipath: eiBGP
  Advertised to non peer-group peers:
  10.0.0.2 10.0.0.3 10.0.0.4 10.0.0.5
  22
    10.0.0.2 (metric 20) from 10.0.0.4 (10.0.0.4)
      Origin IGP, metric 0, localpref 100, valid, internal, multipath
      Extended Community:0x0:0:0 RT:100:1 0x0:0:0
      Originator:10.0.0.2, Cluster list:10.0.0.4
  22
    10.0.0.2 (metric 20) from 10.0.0.5 (10.0.0.5)
      Origin IGP, metric 0, localpref 100, valid, internal, multipath
      Extended Community:0x0:0:0 RT:100:1 0x0:0:0
      Originator:10.0.0.2, Cluster list:10.0.0.5
  22
    10.0.0.2 (metric 20) from 10.0.0.2 (10.0.0.2)
      Origin IGP, metric 0, localpref 100, valid, internal, multipath
      Extended Community:RT:100:1 0x0:0:0
  22
    10.0.0.2 (metric 20) from 10.0.0.3 (10.0.0.3)
      Origin IGP, metric 0, localpref 100, valid, internal, multipath
      Extended Community:0x0:0:0 RT:100:1 0x0:0:0
      Originator:10.0.0.2, Cluster list:10.0.0.3
  22
    10.1.1.12 from 10.1.1.12 (10.22.22.12)
      Origin IGP, metric 0, localpref 100, valid, external, multipath, best
      Extended Community:RT:100:1

Additional References

Related Documents

Related Topic

Document Title

MPLS

MPLS: Layer 3 VPNs: Inter-AS and CSC Configuration Guide, MPLS VPN Carrier Supporting Carrier with BGP

BGP

Cisco IOS IP Routing: BGP Configuration Guide, Configuring BGP

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

--

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

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

RFC 1164

Application of the Border Gateway Protocol in the Internet

RFC 1171

A Border Gateway Protocol 4

RFC 1700

Assigned Numbers

RFC 1966

BGP Route Reflection: An Alternative to Full Mesh IBGP

RFC 2283

Multiprotocol Extensions for BGP-4

RFC 2373

IP Version 6 Addressing Architecture

RFC 2547

BGP/MPLS VPNs

RFC 2842

Capabilities Advertisement with BGP-4

RFC 2858

Multiprotocol Extensions for BGP-4

RFC 3107

Carrying Label Information in BGP-4

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 Load Sharing MPLS VPN Traffic

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 Load Sharing MPLS VPN Traffic

Feature Name

Releases

Feature Configuration Information

MPLS VPN--Load Balancing Support for Inter-AS and CSC VPNs

12.0(29)S

12.4(20)T

This feature allows MPLS VPN Inter-AS and MPLS VPN CSC networks to load share traffic between adjacent LSRs that are connected by multiple links. The LSRs can be a pair of ASBRs or a CSC-PE and a CSC-CE. Using directly connected loopback peering allows load sharing at the IGP level, so more than one BGP session is not needed between the LSRs. No other label distribution mechanism is needed between the adjacent LSRs than BGP.

BGP Multipath Load Sharing for Both eBGP and iBGP in an MPLS VPN

12.2(4)T

12.2(14)S

12.0(24)S

This feature allows multihomed autonomous systems and PE routers to be configured to distribute traffic across both external BGP (eBGP) and internal BGP (iBGP) paths.

iBGP Multipath Load Sharing

12.2(2)T

12.2(14)S

This feature enables the BGP speaking router to select multiple iBGP paths as the best paths to a destination.

eBGP Multipath

12.0(27)S

This feature installs multiple paths in the IP routing table when the eBGP paths are learned from a neighboring Autonomous System (AS), instead of picking one best path.

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

© 2011 Cisco Systems, Inc. All rights reserved.