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Interautonomous System PLS VPN Advanced Concepts

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- The document discusses routing and traffic engineering techniques for inter-autonomous system MPLS VPNs. It describes using route reflectors to exchange routes between sub-autonomous systems and using next-hop-self to modify next-hop attributes. It also covers scaling inter-AS routing with techniques like automatic route filtering and inbound route filtering. Additional topics include downstream route target allocation for filtering, load balancing traffic across multiple inter-AS links, and using redundant PE-ASBR routers.

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INTER-AUTONOMOUS SYSTEM MPLS VPN: ADVANCED CONCEPTS December 2003 MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 1
Agenda • Routing between sub-autonomous systems • Inter-AS scaling • Inter-AS filtering and route distribution • Load balancing • RT rewrite • Services in Inter-AS • Inter-AS and CSC comparison • Inter-AS Summary MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 2
ROUTING BETWEEN SUB-AUTONOMOUS SYSTEMS MPLS VPN Inter-AS, 12/03 Presentation_ID © 2003 Cisco Systems, Inc. All rights reserved. 3
Confederation Multiple IGP Domains • Separate IGPs Each sub-confederations runs a single IGP • Route-reflectors are used as peering points between sub-confederations for better scaling • Next-hop self done by border routers on eBGP and iBGP sessions towards intra-confederation peers MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 4
Confederation Multiple IGP Domains Confederation Sub-AS1 with IGP-1 Sub-AS2 with IGP-2 Core of P LSRs MP-eBGP intra confederation for VPNv4 routes with label distribution Core of P LSRs PE-1 MP-iBGP PE-2 CEGBP-1 PE-3 CEGBP-2 PEs exchange VPNv4 addresses with labels Next-hop and labels are changed (next-hop self is used) CE-1 PE1 and PE-2 addresses are known in both IGPs CE-2 CE-5 CE-4 CE-3 MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 5
Confederation Multiple IGP Domains (Cont.) Confederation Sub-AS1 with IGP-1 Sub-AS2 with IGP-2 Core of P LSRs Core of P LSRs PE-1 Network=RD1:N Next-hop=RR2 Label=L3 Network=RD1:N Next-hop=PE1 Label=L1 PE-2 Network=RD1:N Next-hop=RR1 Label=L2 CEGBP-1 PE-3 CEBGP-2 Network=N Next-hop=PE3 Network=N Next-hop=CE2 CE-2 CE-1 CE-5 CE-3 CE-4 MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 6
Confederation Multiple IGP Domains: Important Points • Route reflectors exchange routes Using Route reflectors is a natural approach since they already have all VPN routes • Next-hop-self choices Option-1: eBGP only Option-2: eBGP and iBGP on border routers • When next-hop self is used on both iBGP and eBGP sessions (in CEBGP-1 and CEBGP-2) the topology is similar to a Multi-provider-VPN topology MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 7
Confederation Multiple IGP Domains: Important Points (Cont.) • CEBGP-1 and CEBGP-2 each need to be known in both IGPs • CEBGP-1 and CEBGP-2 use interface addresses for their BGP session • Label has to be bound on peer address; single label is used between sub-confederations • Neighbor route needs to be known either a static router, or by using PPP neighbor-route discovery • Implementation will create a neighbor route for the BGP peer address MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 8
SCALING INTER-PROVIDER SOLUTIONS MPLS VPN Inter-AS, 12/03 Presentation_ID © 2003 Cisco Systems, Inc. All rights reserved. 9
PE-ASBR Memory Consumption PE-ASBR Memory VPNv4 MP-iBGP Sessions No. VPN Routes Memory Consumption MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 10
PE-ASBR Memory Scaling • Potentially large amounts of VPN routing information that may not need to be carried on PE-ASBRs Large percentage will be local VPN prefixes • PE-ASBRs must hold relevant VPN routing information such as VPN prefix details • Two methods available to aid scaling ARF with local VRF import ARF disabled with inbound filtering MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 11
ARF with Local VRF Import • Automatic Route Filtering (ARF) for non-imported routes If RT does not match locally configured import statement then drop the route • Each PE-ASBR holds VRFs for Inter-AS VPNs and imports routes based on RT values • PE-ASBR acts like normal PE routers with MP-eBGP sessions MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 12
ARF with Local VRF Import (Cont.) BGP Memory VRFs Automatic Route Filtering MP-iBGP VPNv4 CEF Memory MPLS Memory Routing Table Memory BGP, CEF, MPLS & RT Memory per-VRF MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 13
ARF Disabled With Inbound Filtering • Automatic Route Filtering (ARF) enabled by default if no VRFs are configured then ALL VPN routes are dropped by the PE-ASBR • Automatic Route Filtering may be disabled with no default BGP route-target filter command within the BGP configuration • Disabling of ARF will cause ALL routes to be accepted by the PE-ASBR Additional filtering mechanisms should be used to drop unwanted routes MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 14
ARF Disabled With Inbound Filtering (Cont.) router bgp 1 ! no bgp default route-target filter ! address-family vpnv4 neighbor 154.27.0.134 activate neighbor 154.27.0.134 send-community extended neighbor 154.27.0.134 route-map vpn-routesfilter in NO Automatic Route Filtering MP-iBGP VPNv4 BGP Memory LFIB Memory VRF & CEF memory not required Routing Table memory not required NO per-VRF CEF or RT Memory, only BGP & LFIB MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 15
Next-Hop-Self Effect On LFIB BGP Memory 1000 prefixes BGP Memory 1000 prefixes BGP Memory 1000 prefixes LFIB Memory 1000 prefixes LFIB Memory 1000 prefixes LFIB memory 1 prefix for BGP nexthop With NHS MP-iBGP VPNv4 Without NHS 1000 prefixes in total Next-hop-self increase amount of LFIB entries on receiving PE-ASBR MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 16
FILTERING AND ROUTER DISTRIBUTION MECHANISMS MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 17
Various Filtering Points In Inter-AS 4. Inbound filtering per-peer OR rr-group RR 3. Automatic route filtering inbound 1. Inbound filtering on PE-ASBR RR PE AS #200 2. Outbound filtering per-peer PE AS #100 RR AS #300 PE 5. Automatic route filtering inbound MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 18
Inbound Filtering On PE-ASBR Blue VPN routes discarded RT 214:27 RT 214:94 NO Automatic Route Filtering RT 214:129 router bgp 1 ! no bgp default route-target filter ! address-family vpnv4 neighbor 154.27.0.134 activate neighbor 154.27.0.134 send-community extended neighbor 154.27.0.134 route-map vpn-routesfilter in ! ip extcommunity-list 1 permit rt 214:27 rt 214:94 ! route-map vpn-routes-filter permit 10 match extcommunity 1 BGP Memory LFIB Memory NO ARF – Filter inbound on per-peer basis MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 19
Outbound Filtering On PE-ASBR address-family vpnv4 neighbor 157.27.0.132 route-map MPeBGP-2 out neighbor 149.27.0.142 route-map MPeBGP-3 out ! route-map MPeBGP-2 permit 10 match extcommunity 214:27 ! route-map MPeBGP-3 permit 10 match extcommunity 214:94 RED VPN AS #200 BGP Table AS #300 GREEN VPN MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 20
Downstream RT Allocation • Inbound and outbound filtering are restrictive with a large number of VPN clients Each RT must be known, and the filters must be established • Changes to VPN client membership will cause configuration changes on PE-ASBRs Each filter must be updated to reflect the addition/deletion of VPN clients • Simplified filtering scheme is needed with a large number of clients Provided with “downstream provider RT allocation” scheme MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 21
Downstream RT Allocation (Cont.) address-family vpnv4 neighbor 154.27.0.134 activate neighbor 154.27.0.134 send-community extended neighbor 154.27.0.134 route-map asbr-routesfilter in neighbor 157.27.0.132 route-map MPeBGP-2 out neighbor 149.27.0.142 route-map MPeBGP-3 out ! ip extcommunity-list 1 permit rt 129:101 rt 129:102 ip extcommunity-list 16 permit rt 129:101 ip extcommunity-list 17 permit rt 129:102 route-map asbr-routes-filter permit 10 match extcommunity 1 ! route-map MPeBGP-2 permit 10 match extcommunity 16 ! route-map MPeBGP-3 permit 10 match extcommunity 17 AS #200 RED VPN RT 129:101 Export RT 129:12001 RT 129:101 AS #100 Export RT 129:12090 RT 129:102 AS #300 RT 129:102 GREEN VPN RED VPN RT 129:12001 GREEN VPN RT 129:12090 MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 22
LOAD BALANCING: DISTRIBUTION OF TRAFFIC LOAD BETWEEN PROVIDERS MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 23
Load Balancing Between Backbones • Balancing of Inter-AS traffic is an important issue for distribution of traffic and redundancy of network design • All Inter-AS traffic must pass through PE-ASBRs As BGP next-hops are reachable via these routers • Multiple links provide traffic distribution These do not provide redundancy due to single point of failure of the PE-ASBR MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 24
VPN Client Traffic Flow PE-ASBR-1 VPN-v4 update: VPN-v4 update: RD:1:27:152.12.4.0/24, RD:1:27:152.12.4.0/24, NH=PE-1 NH=PE-1 RT=1:222, Label=(L1) RT=1:222, Label=(L1) PE-ASBR-2 VPN-v4 updates: NH=PE-ASBR-2 NH=PE-ASBR-2 ALL Inter-AS traffic flows across PE-ASBR-2 to PEASBR-1 link PE-1 BGP, OSPF, RIPv2 BGP, OSPF, RIPv2 152.12.4.0/24,NH=C 152.12.4.0/24,NH=C E-2 E-2 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-1 NH=PE-ASBR-1 CE-2 PE-2 CE-3 VPN-B VPN-B 152.12.4.0/2 4 VPN Client to VPN Client traffic flow via Inter-AS Link MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 25
Load Balancing Between PE-ASBRs Network Y Network Y BGP NH=PE-ASBR-2 LO0 BGP NH=PE-ASBR-2 LO0 Routing Table Routing Table PE-ASBR-2 LO0 via PE-ASBR-2 193.1.1.9 193.1.1.9 via via 193.1.1.13 193.1.1.13 via via 193.1.1.17 193.1.1.17 PE-ASBR-1 PE-ASBR-2 193.1.1.9 Network Y 193.1.1.13 193.1.1.17 Static’s or IGP AND LDP Loopback Interface Loopback Interface BGP peering (Multi-HOP MP-eBGP) between loopbacks Load Balancing across multiple PE-ASBR links MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 26
Redundant PE-ASBR Connections PE-ASBR-1 VPN-v4 update: VPN-v4 update: RD:1:27:152.12.4.0/24, RD:1:27:152.12.4.0/24, NH=PE-1 NH=PE-1 RT=1:222, Label=(L1) RT=1:222, Label=(L1) VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-1 NH=PE-ASBR-1 PE-ASBR-2 RR will choose BGP best path and advertise only this path to receiving clients VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-2 NH=PE-ASBR-2 PE-ASBR-3 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-3 NH=PE-ASBR-3 PE-ASBR-4 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-4 NH=PE-ASBR-4 VPN-v4 VPN-v4 updates: updates: NH=PE-ASBRNH=PE-ASBR4 4 PE-1 VPN-B Inter-site traffic flow VPN-B Redundant PE-ASBR used purely for backup MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 27
Redundant PE-ASBR Load Balancing PE-ASBR-1 VPN-v4 update: VPN-v4 update: RD:1:27:152.12.4.0/24, RD:1:27:152.12.4.0/24, NH=PE-1 NH=PE-1 RT=1:222, Label=(L1) RT=1:222, Label=(L1) VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-1 NH=PE-ASBR-1 PE-ASBR-2 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-2 NH=PE-ASBR-2 PE-ASBR-3 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-4 NH=PE-ASBR-4 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-3 NH=PE-ASBR-3 PE-1 PE-ASBR-4 VPN-B MPLS VPN Inter-AS, 12/03 iBGP multipath support provides ability to load balance between two exit points Network Network 152.12.4.0/24 152.12.4.0/24 BGP NH=PEBGP NH=PEASBR-2 ASBR-2 PEPEASBR-4 ASBR-4 VPN-B Load balancing PE-ASBR links without Route Reflectors © 2003 Cisco Systems, Inc. All rights reserved. 28
RT REWRITE MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 29
RT Rewrite • RTs identify the VRF routing tables into which the prefix carried by the update is to be imported Carried as extended community attributes in bgp-vpnv4 updates • RT Rewrites Supported for VRF export-maps Allow the replacement of route-targets on incoming and outgoing BGP updates Enables Service Providers to customize Route Targets within their network RT replacement can be performed at ASBRs exchanging VPNv4 prefixes RTs can also be replaced by PEs or RRs MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 30
RT Rewrite Memory and Performance Impact • Memory impact should be insignificant, as it modifies the update itself without requiring storage Other transient memory requirements are minimal • Performance impact will depend on the product of the number of updates and the size (length, depth) of the route-map • To perform RT replacement, each extended-community list is examined while matching and again while deleting the RT MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 31
RT Rewrite Sample Configuration Replace RT X with Y • Use BGP inbound or outbound route-map at the receiving PE(ASBR, RR): ip extcommunity-list <X> permit rt c:d  ! route-map extmap permit <#1> match extcommunity X set extcomm-list <X> delete  set extcomm-list <Y> additive <!continue #2 to the next route-map if have more    RT to change. Can use c:* for additional RTs> ! address family vpnv4  neighbor <ASBR IP#> route-map extmap <in/out> MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 32
RT Rewrite Verification Commands • Verify route target replacement show ip bgp vpnv4 [all] • Verifying the Route Target Replacement Policy debug ip bgp updates <ASBR IP Address> MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 33
SHARED SERVICES IN INTER-AS MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 34
Supported Shared Services in Inter-AS • Network Address Translation Address Translation at the egress point of the peering Service Provider is possible • Redundancy (HSRP, VRRP, GLBP) Two ASBRs will reside in a single SP network • IP Address Management and assignment DHCP, ODAP will be supported for Inter-AS • Security AAA Servers • Troubleshoot/Management Ping, Traceroute, SAA, Netflow MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 35
INTER-AS VERSUS CARRIER SUPPORTING CARRIER MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 36
CSC versus Inter-AS Carrier Supporting Carrier • Opportunity: Offer backbone services to peer or smaller carriers Inter-Provider Access • Opportunity: Provide carrier services on behalf of other carriers Carrier A Backbone Carrier Customer Carrier A POP1 MPLS VPN Inter-AS, 12/03 Customer Carrier A POP2 © 2003 Cisco Systems, Inc. All rights reserved. Carrier B 37
CSC versus Inter-AS (Cont.) CSC Inter-AS Client-server topologies Peer-to-peer topologies ISP or MPLS VPN provider is a customer of another MPLS VPN backbone provider Two ISPs peer up providing services to some of the common customer base MPLS VPN backbone services needed between the same carrier POPs Single SP POPs not available in all geographical areas required by their customers Subscribing service provider may or may not have MPLS enabled Participating Providers must support MPLS VPNs Customers sites do not distribute reachability information to the backbone carrier Customers sites distribute reachability information directly to the participating service providers MPLS VPN in a BGP confederation MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 38
INTER-AS SUMMARY MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 39
Inter-AS Summary • Service Providers have deployed Inter-AS for: Scalability purposes Partitioning the network based on services or management boundaries • Some contract work is in progress amongst Service Providers to establish partnership and offer end-end VPN services to the common customer base • Service Provider networks are completely separate Do not need to exchange internal prefix or label information • Each Service Provider establishes a direct MP-eBGP session with the others to exchange VPN-IPv4 addresses with labels • /32 route to reach the ASBR is created by default so ASBRs can communicate without a need for IGP Must be redistributed in the receiving Service Provider’s IGP MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 40
Inter-AS Summary (Cont.) • IGP or LDP across ASBR links is not required Labels are already assigned to the routes when exchanged via MP-eBGP Interface used to establish MP-eBGP session does not need to be associated with a VRF • Direct eBGP routes and labels can be exchanged. • Next-Hop self can be turned on on ASBRs, enabling the ASBR to use its own address for next-hop • Using the next-hop self requires an additional entry in the TFIB for each VPNv4 route (about 180) bytes • If the Service Provider wishes to hide the Inter-AS link then use the next-hop-self method otherwise use the redistribute connected subnets method MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 41
Inter-AS Summary (Cont.) • Multi-hop MP-eBGP sessions can be passed between Service Providers without conversions to VPNv4 routes • Configuration of VRFs is not required on the ASBRs because bgp default route-target filter (automatic route filtering feature) has been disabled • To conserve memory on both sides of the boundary and implement a simple form of security, always configure inbound route-maps to filter only routes that need to be passed to the other AS MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 42
References • Inter-AS for MPLS VPNs CCO Documentation: www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121 • MPLS and VPN architectures Jim Guichard/Ivan Pepelnjak ISBN 1-58705-002-1: www.ciscopress.com/book.cfm?book=168 • Support for Inter-provider MPLS VPN ENG-48803 Dan Tappan, (internal only) MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 43
MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 44

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Interautonomous System PLS VPN Advanced Concepts

  • 1. INTER-AUTONOMOUS SYSTEM MPLS VPN: ADVANCED CONCEPTS December 2003 MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 1
  • 2. Agenda • Routing between sub-autonomous systems • Inter-AS scaling • Inter-AS filtering and route distribution • Load balancing • RT rewrite • Services in Inter-AS • Inter-AS and CSC comparison • Inter-AS Summary MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 2
  • 3. ROUTING BETWEEN SUB-AUTONOMOUS SYSTEMS MPLS VPN Inter-AS, 12/03 Presentation_ID © 2003 Cisco Systems, Inc. All rights reserved. 3
  • 4. Confederation Multiple IGP Domains • Separate IGPs Each sub-confederations runs a single IGP • Route-reflectors are used as peering points between sub-confederations for better scaling • Next-hop self done by border routers on eBGP and iBGP sessions towards intra-confederation peers MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 4
  • 5. Confederation Multiple IGP Domains Confederation Sub-AS1 with IGP-1 Sub-AS2 with IGP-2 Core of P LSRs MP-eBGP intra confederation for VPNv4 routes with label distribution Core of P LSRs PE-1 MP-iBGP PE-2 CEGBP-1 PE-3 CEGBP-2 PEs exchange VPNv4 addresses with labels Next-hop and labels are changed (next-hop self is used) CE-1 PE1 and PE-2 addresses are known in both IGPs CE-2 CE-5 CE-4 CE-3 MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 5
  • 6. Confederation Multiple IGP Domains (Cont.) Confederation Sub-AS1 with IGP-1 Sub-AS2 with IGP-2 Core of P LSRs Core of P LSRs PE-1 Network=RD1:N Next-hop=RR2 Label=L3 Network=RD1:N Next-hop=PE1 Label=L1 PE-2 Network=RD1:N Next-hop=RR1 Label=L2 CEGBP-1 PE-3 CEBGP-2 Network=N Next-hop=PE3 Network=N Next-hop=CE2 CE-2 CE-1 CE-5 CE-3 CE-4 MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 6
  • 7. Confederation Multiple IGP Domains: Important Points • Route reflectors exchange routes Using Route reflectors is a natural approach since they already have all VPN routes • Next-hop-self choices Option-1: eBGP only Option-2: eBGP and iBGP on border routers • When next-hop self is used on both iBGP and eBGP sessions (in CEBGP-1 and CEBGP-2) the topology is similar to a Multi-provider-VPN topology MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 7
  • 8. Confederation Multiple IGP Domains: Important Points (Cont.) • CEBGP-1 and CEBGP-2 each need to be known in both IGPs • CEBGP-1 and CEBGP-2 use interface addresses for their BGP session • Label has to be bound on peer address; single label is used between sub-confederations • Neighbor route needs to be known either a static router, or by using PPP neighbor-route discovery • Implementation will create a neighbor route for the BGP peer address MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 8
  • 9. SCALING INTER-PROVIDER SOLUTIONS MPLS VPN Inter-AS, 12/03 Presentation_ID © 2003 Cisco Systems, Inc. All rights reserved. 9
  • 10. PE-ASBR Memory Consumption PE-ASBR Memory VPNv4 MP-iBGP Sessions No. VPN Routes Memory Consumption MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 10
  • 11. PE-ASBR Memory Scaling • Potentially large amounts of VPN routing information that may not need to be carried on PE-ASBRs Large percentage will be local VPN prefixes • PE-ASBRs must hold relevant VPN routing information such as VPN prefix details • Two methods available to aid scaling ARF with local VRF import ARF disabled with inbound filtering MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 11
  • 12. ARF with Local VRF Import • Automatic Route Filtering (ARF) for non-imported routes If RT does not match locally configured import statement then drop the route • Each PE-ASBR holds VRFs for Inter-AS VPNs and imports routes based on RT values • PE-ASBR acts like normal PE routers with MP-eBGP sessions MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 12
  • 13. ARF with Local VRF Import (Cont.) BGP Memory VRFs Automatic Route Filtering MP-iBGP VPNv4 CEF Memory MPLS Memory Routing Table Memory BGP, CEF, MPLS & RT Memory per-VRF MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 13
  • 14. ARF Disabled With Inbound Filtering • Automatic Route Filtering (ARF) enabled by default if no VRFs are configured then ALL VPN routes are dropped by the PE-ASBR • Automatic Route Filtering may be disabled with no default BGP route-target filter command within the BGP configuration • Disabling of ARF will cause ALL routes to be accepted by the PE-ASBR Additional filtering mechanisms should be used to drop unwanted routes MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 14
  • 15. ARF Disabled With Inbound Filtering (Cont.) router bgp 1 ! no bgp default route-target filter ! address-family vpnv4 neighbor 154.27.0.134 activate neighbor 154.27.0.134 send-community extended neighbor 154.27.0.134 route-map vpn-routesfilter in NO Automatic Route Filtering MP-iBGP VPNv4 BGP Memory LFIB Memory VRF & CEF memory not required Routing Table memory not required NO per-VRF CEF or RT Memory, only BGP & LFIB MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 15
  • 16. Next-Hop-Self Effect On LFIB BGP Memory 1000 prefixes BGP Memory 1000 prefixes BGP Memory 1000 prefixes LFIB Memory 1000 prefixes LFIB Memory 1000 prefixes LFIB memory 1 prefix for BGP nexthop With NHS MP-iBGP VPNv4 Without NHS 1000 prefixes in total Next-hop-self increase amount of LFIB entries on receiving PE-ASBR MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 16
  • 17. FILTERING AND ROUTER DISTRIBUTION MECHANISMS MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 17
  • 18. Various Filtering Points In Inter-AS 4. Inbound filtering per-peer OR rr-group RR 3. Automatic route filtering inbound 1. Inbound filtering on PE-ASBR RR PE AS #200 2. Outbound filtering per-peer PE AS #100 RR AS #300 PE 5. Automatic route filtering inbound MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 18
  • 19. Inbound Filtering On PE-ASBR Blue VPN routes discarded RT 214:27 RT 214:94 NO Automatic Route Filtering RT 214:129 router bgp 1 ! no bgp default route-target filter ! address-family vpnv4 neighbor 154.27.0.134 activate neighbor 154.27.0.134 send-community extended neighbor 154.27.0.134 route-map vpn-routesfilter in ! ip extcommunity-list 1 permit rt 214:27 rt 214:94 ! route-map vpn-routes-filter permit 10 match extcommunity 1 BGP Memory LFIB Memory NO ARF – Filter inbound on per-peer basis MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 19
  • 20. Outbound Filtering On PE-ASBR address-family vpnv4 neighbor 157.27.0.132 route-map MPeBGP-2 out neighbor 149.27.0.142 route-map MPeBGP-3 out ! route-map MPeBGP-2 permit 10 match extcommunity 214:27 ! route-map MPeBGP-3 permit 10 match extcommunity 214:94 RED VPN AS #200 BGP Table AS #300 GREEN VPN MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 20
  • 21. Downstream RT Allocation • Inbound and outbound filtering are restrictive with a large number of VPN clients Each RT must be known, and the filters must be established • Changes to VPN client membership will cause configuration changes on PE-ASBRs Each filter must be updated to reflect the addition/deletion of VPN clients • Simplified filtering scheme is needed with a large number of clients Provided with “downstream provider RT allocation” scheme MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 21
  • 22. Downstream RT Allocation (Cont.) address-family vpnv4 neighbor 154.27.0.134 activate neighbor 154.27.0.134 send-community extended neighbor 154.27.0.134 route-map asbr-routesfilter in neighbor 157.27.0.132 route-map MPeBGP-2 out neighbor 149.27.0.142 route-map MPeBGP-3 out ! ip extcommunity-list 1 permit rt 129:101 rt 129:102 ip extcommunity-list 16 permit rt 129:101 ip extcommunity-list 17 permit rt 129:102 route-map asbr-routes-filter permit 10 match extcommunity 1 ! route-map MPeBGP-2 permit 10 match extcommunity 16 ! route-map MPeBGP-3 permit 10 match extcommunity 17 AS #200 RED VPN RT 129:101 Export RT 129:12001 RT 129:101 AS #100 Export RT 129:12090 RT 129:102 AS #300 RT 129:102 GREEN VPN RED VPN RT 129:12001 GREEN VPN RT 129:12090 MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 22
  • 23. LOAD BALANCING: DISTRIBUTION OF TRAFFIC LOAD BETWEEN PROVIDERS MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 23
  • 24. Load Balancing Between Backbones • Balancing of Inter-AS traffic is an important issue for distribution of traffic and redundancy of network design • All Inter-AS traffic must pass through PE-ASBRs As BGP next-hops are reachable via these routers • Multiple links provide traffic distribution These do not provide redundancy due to single point of failure of the PE-ASBR MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 24
  • 25. VPN Client Traffic Flow PE-ASBR-1 VPN-v4 update: VPN-v4 update: RD:1:27:152.12.4.0/24, RD:1:27:152.12.4.0/24, NH=PE-1 NH=PE-1 RT=1:222, Label=(L1) RT=1:222, Label=(L1) PE-ASBR-2 VPN-v4 updates: NH=PE-ASBR-2 NH=PE-ASBR-2 ALL Inter-AS traffic flows across PE-ASBR-2 to PEASBR-1 link PE-1 BGP, OSPF, RIPv2 BGP, OSPF, RIPv2 152.12.4.0/24,NH=C 152.12.4.0/24,NH=C E-2 E-2 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-1 NH=PE-ASBR-1 CE-2 PE-2 CE-3 VPN-B VPN-B 152.12.4.0/2 4 VPN Client to VPN Client traffic flow via Inter-AS Link MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 25
  • 26. Load Balancing Between PE-ASBRs Network Y Network Y BGP NH=PE-ASBR-2 LO0 BGP NH=PE-ASBR-2 LO0 Routing Table Routing Table PE-ASBR-2 LO0 via PE-ASBR-2 193.1.1.9 193.1.1.9 via via 193.1.1.13 193.1.1.13 via via 193.1.1.17 193.1.1.17 PE-ASBR-1 PE-ASBR-2 193.1.1.9 Network Y 193.1.1.13 193.1.1.17 Static’s or IGP AND LDP Loopback Interface Loopback Interface BGP peering (Multi-HOP MP-eBGP) between loopbacks Load Balancing across multiple PE-ASBR links MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 26
  • 27. Redundant PE-ASBR Connections PE-ASBR-1 VPN-v4 update: VPN-v4 update: RD:1:27:152.12.4.0/24, RD:1:27:152.12.4.0/24, NH=PE-1 NH=PE-1 RT=1:222, Label=(L1) RT=1:222, Label=(L1) VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-1 NH=PE-ASBR-1 PE-ASBR-2 RR will choose BGP best path and advertise only this path to receiving clients VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-2 NH=PE-ASBR-2 PE-ASBR-3 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-3 NH=PE-ASBR-3 PE-ASBR-4 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-4 NH=PE-ASBR-4 VPN-v4 VPN-v4 updates: updates: NH=PE-ASBRNH=PE-ASBR4 4 PE-1 VPN-B Inter-site traffic flow VPN-B Redundant PE-ASBR used purely for backup MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 27
  • 28. Redundant PE-ASBR Load Balancing PE-ASBR-1 VPN-v4 update: VPN-v4 update: RD:1:27:152.12.4.0/24, RD:1:27:152.12.4.0/24, NH=PE-1 NH=PE-1 RT=1:222, Label=(L1) RT=1:222, Label=(L1) VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-1 NH=PE-ASBR-1 PE-ASBR-2 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-2 NH=PE-ASBR-2 PE-ASBR-3 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-4 NH=PE-ASBR-4 VPN-v4 updates: VPN-v4 updates: NH=PE-ASBR-3 NH=PE-ASBR-3 PE-1 PE-ASBR-4 VPN-B MPLS VPN Inter-AS, 12/03 iBGP multipath support provides ability to load balance between two exit points Network Network 152.12.4.0/24 152.12.4.0/24 BGP NH=PEBGP NH=PEASBR-2 ASBR-2 PEPEASBR-4 ASBR-4 VPN-B Load balancing PE-ASBR links without Route Reflectors © 2003 Cisco Systems, Inc. All rights reserved. 28
  • 29. RT REWRITE MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 29
  • 30. RT Rewrite • RTs identify the VRF routing tables into which the prefix carried by the update is to be imported Carried as extended community attributes in bgp-vpnv4 updates • RT Rewrites Supported for VRF export-maps Allow the replacement of route-targets on incoming and outgoing BGP updates Enables Service Providers to customize Route Targets within their network RT replacement can be performed at ASBRs exchanging VPNv4 prefixes RTs can also be replaced by PEs or RRs MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 30
  • 31. RT Rewrite Memory and Performance Impact • Memory impact should be insignificant, as it modifies the update itself without requiring storage Other transient memory requirements are minimal • Performance impact will depend on the product of the number of updates and the size (length, depth) of the route-map • To perform RT replacement, each extended-community list is examined while matching and again while deleting the RT MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 31
  • 32. RT Rewrite Sample Configuration Replace RT X with Y • Use BGP inbound or outbound route-map at the receiving PE(ASBR, RR): ip extcommunity-list <X> permit rt c:d  ! route-map extmap permit <#1> match extcommunity X set extcomm-list <X> delete  set extcomm-list <Y> additive <!continue #2 to the next route-map if have more    RT to change. Can use c:* for additional RTs> ! address family vpnv4  neighbor <ASBR IP#> route-map extmap <in/out> MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 32
  • 33. RT Rewrite Verification Commands • Verify route target replacement show ip bgp vpnv4 [all] • Verifying the Route Target Replacement Policy debug ip bgp updates <ASBR IP Address> MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 33
  • 34. SHARED SERVICES IN INTER-AS MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 34
  • 35. Supported Shared Services in Inter-AS • Network Address Translation Address Translation at the egress point of the peering Service Provider is possible • Redundancy (HSRP, VRRP, GLBP) Two ASBRs will reside in a single SP network • IP Address Management and assignment DHCP, ODAP will be supported for Inter-AS • Security AAA Servers • Troubleshoot/Management Ping, Traceroute, SAA, Netflow MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 35
  • 36. INTER-AS VERSUS CARRIER SUPPORTING CARRIER MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 36
  • 37. CSC versus Inter-AS Carrier Supporting Carrier • Opportunity: Offer backbone services to peer or smaller carriers Inter-Provider Access • Opportunity: Provide carrier services on behalf of other carriers Carrier A Backbone Carrier Customer Carrier A POP1 MPLS VPN Inter-AS, 12/03 Customer Carrier A POP2 © 2003 Cisco Systems, Inc. All rights reserved. Carrier B 37
  • 38. CSC versus Inter-AS (Cont.) CSC Inter-AS Client-server topologies Peer-to-peer topologies ISP or MPLS VPN provider is a customer of another MPLS VPN backbone provider Two ISPs peer up providing services to some of the common customer base MPLS VPN backbone services needed between the same carrier POPs Single SP POPs not available in all geographical areas required by their customers Subscribing service provider may or may not have MPLS enabled Participating Providers must support MPLS VPNs Customers sites do not distribute reachability information to the backbone carrier Customers sites distribute reachability information directly to the participating service providers MPLS VPN in a BGP confederation MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 38
  • 39. INTER-AS SUMMARY MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 39
  • 40. Inter-AS Summary • Service Providers have deployed Inter-AS for: Scalability purposes Partitioning the network based on services or management boundaries • Some contract work is in progress amongst Service Providers to establish partnership and offer end-end VPN services to the common customer base • Service Provider networks are completely separate Do not need to exchange internal prefix or label information • Each Service Provider establishes a direct MP-eBGP session with the others to exchange VPN-IPv4 addresses with labels • /32 route to reach the ASBR is created by default so ASBRs can communicate without a need for IGP Must be redistributed in the receiving Service Provider’s IGP MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 40
  • 41. Inter-AS Summary (Cont.) • IGP or LDP across ASBR links is not required Labels are already assigned to the routes when exchanged via MP-eBGP Interface used to establish MP-eBGP session does not need to be associated with a VRF • Direct eBGP routes and labels can be exchanged. • Next-Hop self can be turned on on ASBRs, enabling the ASBR to use its own address for next-hop • Using the next-hop self requires an additional entry in the TFIB for each VPNv4 route (about 180) bytes • If the Service Provider wishes to hide the Inter-AS link then use the next-hop-self method otherwise use the redistribute connected subnets method MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 41
  • 42. Inter-AS Summary (Cont.) • Multi-hop MP-eBGP sessions can be passed between Service Providers without conversions to VPNv4 routes • Configuration of VRFs is not required on the ASBRs because bgp default route-target filter (automatic route filtering feature) has been disabled • To conserve memory on both sides of the boundary and implement a simple form of security, always configure inbound route-maps to filter only routes that need to be passed to the other AS MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 42
  • 43. References • Inter-AS for MPLS VPNs CCO Documentation: www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121 • MPLS and VPN architectures Jim Guichard/Ivan Pepelnjak ISBN 1-58705-002-1: www.ciscopress.com/book.cfm?book=168 • Support for Inter-provider MPLS VPN ENG-48803 Dan Tappan, (internal only) MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 43
  • 44. MPLS VPN Inter-AS, 12/03 © 2003 Cisco Systems, Inc. All rights reserved. 44

Editor's Notes

  • #5: &lt;number&gt;
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  • #17: Note that route/path combination in LFIB requires 168 bytes of memory – with 1000 prefixes this is 164k
  • #23: Note that you need two export statements or you can use export maps without any route-target export commands within the VRF configuration
  • #27: Note that this requires Multi-HOP MP-eBGP between PE-ASBR routers. Also note CSCdt70169 as this configuration may be broken in current releases.
  • #28: Note that local-preference or weight could also be used as a tool at PE-ASBR-2 and PE-ASBR-4.
  • #29: This slide shows how to load balance across multiple PE-ASBR links but shows that route reflectors cannot be used in this case which 99% of the time is not going to be an acceptable deployment solution – therefore the ability to propagate multiple exit points via the route reflectors is a requirement
  • #31: Both the above changes will require a slight modification of the BGP update processing path - Support for imposing RTs on incoming/outgoing updates. This is currently supported for VRF export-maps, but support needs to be extended to BGP inbound/outbound route-maps. The memory impact of this feature should be insignificant as it modifies the update itself without requiring the storage of the update. Also, other transient memory requirements are minimal. The performance impact will depend on the length of the route-map. For each update, to perform RT replacement, each extended-community list being used will have to be walked twice, once while matching and once while deleting the RT. The performance impact will depend on the product of the number of updates and the size of the route-map. This is true for any route-map related feature.
  • #32: The memory impact of this feature should be insignificant as it modifies the update itself without requiring the storage of the update. Also, other transient memory requirements are minimal. The performance impact will depend on the length of the route-map. For each update, to perform RT replacement, each extended-community list being used will have to be walked twice, once while matching and once while deleting the RT. The performance impact will depend on the product of the number of updates and the size of the route-map. This is true for any route-map related feature.
  • #34: Router# &lt;B&amp;NBSP;STYLE=&quot;FONT-WEIGHT:&amp;NBSP;BOLD&quot;&gt;show ip bgp vpnv4 all 172.16.17.17 BGP routing table entry for 100:1:172.16.17.17/32, version 6 Paths: (1 available, best #1, no table)   Advertised to update-groups:      1            100 300     192.168.1.1 from 192.168.1.1 (172.16.13.13)       Origin incomplete, localpref 100, valid, external, best       Extended Community: RT:100:1 The following examples verify route target replacement on PE1 and PE2. Verify route target on PE1: Router# &lt;B&amp;NBSP;STYLE=&quot;FONT-WEIGHT:&amp;NBSP;BOLD&quot;&gt;show ip bgp vpnv4 all 172.16.17.17 BGP routing table entry for 100:1:172.16.17.17/32, version 13 Paths: (1 available, best #1, table vpn1)   Advertised to update-groups:      1            300     192.168.2.1 (via vpn1) from 192.168.2.1 (172.16.19.19)       Origin incomplete, metric 0, localpref 100, valid, external, best       Extended Community: RT:200:1 Verify route target on PE2: Router# &lt;B&amp;NBSP;STYLE=&quot;FONT-WEIGHT:&amp;NBSP;BOLD&quot;&gt;show ip bgp vpnv4 all 172.16.17.17 BGP routing table entry for 100:1:172.16.17.17/32, version 13 Paths: (1 available, best #1, table vpn1)   Advertised to update-groups:      3            100 300     192.168.1.1 (metric 20) from 172.16.16.16 (172.16.16.16)       Origin incomplete, localpref 100, valid, internal, best       Extended Community: RT:100:1 ========================================================
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