[c-nsp] Cisco BGP Multipath Load Sharing for Both eBGP and iBGP in an MPLS-VPN / MPLS VPN--BGP Local Convergence

[Youssef Bengelloun-Zahr]

Hello Community,

I am trying / testing the following features :

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

- MPLS VPN--BGP Local Convergence

The objective is to provide our clients L3 VPN/MPLS clients with :

        - Simple redundancy (active DSL link / backup DSL link).

        - load-balancing + redundancy (active DSL link / active DSL link )

The clients access our core network using DSL links (PPPoVPDN technology).


I have re-created a partial portion of our backbone using GNS3 (Hey ! I only
have limited resources ;-).

Here is the details of the lab :

- Routers used : c7206 VXR with NPE-400

- IOS : c7200-adventerprisek9-mz.122-33.SRD

- Topology :

         * PE1, PE2, PE3 peer using BGP with a P router (IPV4, VPNv4, Route
Reflexion).

         * CPE1 is multihomed (connected with PE1 and PE2), configured with
loopback 1.1.1.1

         * CPE2 is monohomed (connnected with PE3), configured with loopback
2.2.2.2

I use static routes in order the loopback on CPEs. Here is a sample of the
configuration of the VRF on one PE :

PE1#sh run vrf toto
Building configuration...

Current configuration : 627 bytes
ip vrf toto
 description vrf toto
 rd 42937:501
 route-target export 42937:501
 route-target import 42937:501
 *protection local-prefixes*
!
!
interface FastEthernet1/0
 description F=C, E=CPE1, P=Fa0/0
 ip vrf forwarding toto
 ip address 172.16.0.1 255.255.255.252
 speed 100
 duplex full
!
interface Loopback501
 description toto
 ip vrf forwarding toto
 ip address 10.200.1.241 255.255.255.255
!
router bgp 65432
 !
 address-family ipv4 vrf toto
  no synchronization
  redistribute connected
  redistribute static
  *maximum-paths ibgp 5*
 exit-address-family
!
ip route vrf toto 1.1.1.1 255.255.255.255 172.16.0.2 track 1



My sources :

http://www.cisco.com/en/US/docs/ios/mpls/configuration/guide/mp_vpn_pece_lnk_prot.html

http://www.cisco.com/en/US/docs/ios/iproute_bgp/configuration/guide/irg_ebgp_ibgp.html

http://www.cisco.com/en/US/docs/ios/mpls/configuration/guide/mp_load_share_vpn.html

http://www-europe.cisco.com/en/US/docs/ios/iproute_bgp/configuration/guide/irg_multi_load_ps6922_TSD_Products_Configuration_Guide_Chapter.html


I have been reading a lot concerning theese features and one statement got
me thinking (link 3) :

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.


For the sake of pragmatism, I have tested it and things look to be working
just fine. But, here is what I get when I remove label sending :

*Apr 13 15:26:08.307: %BGP_MPLS-6-MPLS_INIT: MPLS has been disabled for the
BGP address-family IPv4 Unicast
*Apr 13 15:26:08.315: %BGP-5-ADJCHANGE: neighbor 77.246.80.1 Down Capability
changed

Question is :

- Do I need to configure this ?

- Do I need to send labels from the PEs to the Ps? from the Ps to the PEs ?
both ?



Finally, do any of you guys use theese outside there ? Any feedbacks ?


Thank you for your time and you patience.

Best regards.

Y.

-- 
Youssef BENGELLOUN-ZAHR ………………………………………………
Ingénieur Réseaux et Télécoms


Technopole de l'Aube  en Champagne - BP 601 - 10901 TROYES  Cedex 9
Agence Paris : 6, rue Charles Floquet - 92120 MONTROUGE
Tel                 +33 (0) 825 000 720
Tel. direct      +33 (0) 1 77 35 59 14
Tel. portable  +33 (0) 6 22 42 63 80
Email            ybz at 720.fr
……………………………………………………………………………….....www.720.fr