1 © 2001, Cisco Systems, Inc. All rights reserved. Session Number Presentation_ID MPLS Introduction.

333 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 3 MPLS Concept In Core: Forward using labels (as opposed to IP addr) Label indicates service class and destination Label Switch Router (LSR) Router ATM switch + Tag Switch Controller Label Distribution Protocol (LDP) Edge Label Switch Router (ATM Switch or Router) At Edge: Classify packets Label them

444 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 4 MPLS concept MPLS: Multi Protocol Label Switching Packet forwarding is done based on Labels. Labels are assigned when the packet enters into the network. Labels are on top of the packet. MPLS nodes forward packets/cells based on the label value (not on the IP information).

555 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 5 MPLS concept MPLS allows: Packet classification only where the packet enters the network. The packet classification is encoded as a label. In the core, packets are forwarded without having to re-classify them. - No further packet analysis - Label swapping

666 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 6 MPLS Operation 1a. Existing routing protocols (e.g. OSPF, IS-IS) establish reachability to destination networks. 1b. Label Distribution Protocol (LDP) establishes label to destination network mappings. 2. Ingress Edge LSR receives packet, performs Layer 3 value-added services, and labels(PUSH) packets. 3. LSR switches packets using label swapping(SWAP). 4. Edge LSR at egress removes(POP) label and delivers packet.

777 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 7 Label Switch Path (LSP) LSPs are derived from IGP routing information LSPs may diverge from IGP shortest path LSPs are unidirectional Return traffic takes another LSP LSP follows IGP shortest pathLSP diverges from IGP shortest path IGP domain with a label distribution protocol

888 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 8 Encapsulations Label Header PPP Header Layer 3 Header PPP Header (Packet over SONET/SDH) ATM Cell Header HEC Label DATA CLP PTI VCI GFC VPI Label Header MAC Header Layer 3 Header LAN MAC Label Header

999 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 9 Label Header Header= 4 bytes, Label = 20 bits. Can be used over Ethernet, 802.3, or PPP links Contains everything needed at forwarding time Label = 20 bits EXP = Class of Service, 3 bits S = Bottom of Stack, 1 bitTTL = Time to Live, 8 bits 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 LabelEXPSTTL

10 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 10 Loops and TTL In IP networks TTL is used to prevent packets to travel indefinitely in the network MPLS may use same mechanism as IP, but not on all encapsulations TTL is present in the label header for PPP and LAN headers (shim headers) ATM cell header does not have TTL

11 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 11 Loops and TTL IP TTL is copied to MPLS TTL header and decremented in each MPLS router, and copied again to the IP at the Egress (or in the hop before). If TTL is 0 the packet is discarded at the ingress point TTL is examined at the LSP exit IGP domain with a label distribution protocol LSR-1 LSR-2 LSR-4 LSR-5 LSR- 3 LSR-6 Egress IP packet TTL = 10 Label = 25 IP packet TTL = 6 IP packet TTL = 10 LSR-6 --> 25 Hops=4 IP packet TTL = 10 Label = 39 IP packet TTL = 10 Label = 21

12 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 12 Label Assignment and Distribution Labels have link-local significance: Each LSR binds his own label mappings Each LSR assign labels to his FECs Labels are assigned and exchanged between adjacent neighboring LSR

13 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 13 Label Assignment and Distribution Rtr-C is the downstream neighbor of Rtr-B for destination 171.68.10/24 Rtr-B is the downstream neighbor of Rtr-A for destination 171.68.10/24 LSRs know their downstream neighbors through the IP routing protocol Next-hop address is the downstream neighbor 171.68.10/24 Rtr-BRtr-ARtr-C 171.68.40/24 Upstream and Downstream LSRs

14 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 14 Unsolicited Downstream Distribution LSRs distribute labels to the upstream neighbors 171.68.10/24 Rtr-B Rtr-A Rtr-C 171.68.40/24 Next-Hop InLab -... AddressPrefix 171.68.10... OutI/F 1... OutLab 30... InI/F 0... Next-Hop InLab 30... AddressPrefix 171.68.10... OutI/F 1... OutLab 40... InI/F 0... Next-Hop InLab 40... AddressPrefix 171.68.10... OutI/F 1... OutLab -... InI/F 0... Use label 40 for destination 171.68.10/24 Use label 30 for destination 171.68.10/24 IGP derived routes

15 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 15 On-Demand Downstream Distribution Upstream LSRs request labels to downstream neighbors Downstream LSRs distribute labels upon request 171.68.10/24 Rtr-B Rtr-A Rtr-C 171.68.40/24 Use label 30 for destination 171.68.10/24 Use label 40 for destination 171.68.10/24 Request label for destination 171.68.10/24

16 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 16 Liberal retention mode LSR retains labels from all neighbors Improve convergence time, when next-hop is again available after IP convergence Require more memory and label space Conservative retention mode LSR retains labels only from next-hops neighbors LSR discards all labels for FECs without next-hop Free memory and label space Label Retention Modes

17 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 17 Independent LSP control LSR binds a Label to a FEC independently, whether or not the LSR has received a Label the next-hop for the FEC The LSR then advertises the Label to its neighbor Ordered LSP control LSR only binds and advertise a label for a particular FEC if: it is the egress LSR for that FEC or it has already received a label binding from its next-hop Label Distribution Modes

18 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 18 Router Example: Forwarding Packets 0 171.69 Packets Forwarded Based on IP Address Data Address Prefix 128.89 171.69 1 1 I/F … Address Prefix 128.89 171.69 0 1 … 0 1 I/F 128.89 0 1 128.89.25.4Data Address Prefix 128.89 0 …… I/F Data 128.89.25.4

19 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 19 MPLS Example: Routing Information 128.89 1 0 1 0 Routing Updates (OSPF, EIGRP, …) You Can Reach 128.89 and 171.69 Thru Me You Can Reach 171.69 Thru Me You Can Reach 128.89 Thru Me In Label Address Prefix 128.89 171.69 1 1 Out I’face Out Label In Label Address Prefix 128.89 171.69 0 1 Out I’face Out Label In Label Address Prefix 128.890 Out I’face Out Label ……………… 171.69

20 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 20 MPLS Example: Assigning Labels 128.89 1 0 1 0 Label Distribution Protocol (LDP) (downstream allocation) Use Label 4 for 128.89 and Use Label 5 for 171.69 Use Label 7 for 171.69 Use Label 9 for 128.89 In Label Address Prefix 128.89 171.69 1 1 Out I’face Out Label In Label Address Prefix 128.89 171.69 0 1 Out I’face Out Label In Label Address Prefix 128.890 Out I’face Out Label -9 ……………………………… 9 7 4 5 4 5 - - 171.69

21 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 21 In Label Address Prefix 128.89 171.69 1 1 Out I’face Out Label ………… 4 5 - - MPLS Example: Forwarding Packets Label Switch Forwards Based on Label In Label Address Prefix 128.89 171.69 0 1 Out I’face Out Label ………… 9 7 4 4 5 In Label Address Prefix 128.890 Out I’face Out Label -9 ………… Data128.89.25.4Data 128.89.25.4Data 128.89.25.4Data 128.89 1 0 1 0 128.89.25.4 4 4 9 9

23 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 23 MPLS Unicast IP Routing MPLS introduces a new field that is used for forwarding decisions. Although labels are locally significant, they have to be advertised to directly reachable peers. One option would be to include this parameter into existing IP routing protocols. The other option is to create a new protocol to exchange labels. The second option has been used because there are too many existing IP routing protocols that would have to be modified to carry labels.

24 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 24 Label Distribution Protocol Defined in RFC 3036 and 3037 Used to distribute labels in a MPLS network Forwarding equivalence class How packets are mapped to LSPs (Label Switched Paths) Advertise labels per FEC Reach destination a.b.c.d with label x Neighbor discovery Basic and extended discovery

25 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 25 MPLS Unicast IP Routing Architecture LSR Control plane Data plane Routing protocol Label distribution protocol Label forwarding table IP routing table Exchange of routing information Exchange of labels Incoming labeled packets Outgoing labeled packets IP forwarding table Incoming IP packets Outgoing IP packets

26 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 26 MPLS Unicast IP Routing: Example LSR Control plane Data plane OSPF: RT: LIB: FIB: LFIB: OSPF: 10.0.0.0/8 10.0.0.0/8  1.2.3.4 L=5 10.1.1.110.1.1.1

27 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 27 MPLS Unicast IP Routing: Example LSR Control plane Data plane OSPF: RT: LIB: FIB: LFIB: OSPF: 10.0.0.0/8 10.0.0.0/8  1.2.3.4 10.1.1.1 LDP: 10.0.0.0/8, L=3 L=5 10.1.1.1 10.0.0.0/8  Next-hop L=3, Local L=5 LDP: 10.0.0.0/8, L=5 L=3 10.1.1.1 L=5  L=3, L=3

28 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 28 Label Allocation in Packet-Mode MPLS Environment Label allocation and distribution in packet-mode MPLS environment follows these steps: 1. IP routing protocols build the IP routing table. 2. Each LSR assigns a label to every destination in the IP routing table independently. 3. LSRs announce their assigned labels to all other LSRs. 4. Every LSR builds its LIB, LFIB data structures based on received labels.

29 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 29 Building the IP Routing Table IP routing protocols are used to build IP routing tables on all LSRs. Forwarding tables (FIB) are built based on IP routing tables with no labeling information.

30 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 30 Allocating Labels Every LSR allocates a label for every destination in the IP routing table. Labels have local significance. Label allocations are asynchronous. Router B assigns label 25 to destination X.

31 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 31 LIB and LFIB Set-up LIB and LFIB structures have to be initialized on the LSR allocating the label. Router B assigns label 25 to destination X. Outgoing action is POP as B has received no label for X from C. Local label is stored in LIB.

32 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 32 Label Distribution The allocated label is advertised to all neighbor LSRs, regardless of whether the neighbors are upstream or downstream LSRs for the destination. X = 25

33 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 33 Receiving Label Advertisement Every LSR stores the received label in its LIB. Edge LSRs that receive the label from their next-hop also store the label information in the FIB. X = 25

34 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 34 Interim Packet Propagation Forwarded IP packets are labeled only on the path segments where the labels have already been assigned. ABC E IP: XLab: 25IP: X IP lookup is performed in FIB, packet is labeled. Label lookup is performed in LFIB, label is removed.

35 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 35 Further Label Allocation Every LSR will eventually assign a label for every destination. Router C assigns label 47 to destination X. X = 47

36 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 36 Receiving Label Advertisement Every LSR stores received information in its LIB. LSRs that receive their label from their next-hop LSR will also populate the IP forwarding table (FIB). X = 47

37 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 37 Populating LFIB Router B has already assigned label to X and created an entry in LFIB. Outgoing label is inserted in LFIB after the label is received from the next-hop LSR. X = 47 LabelActionNext hop 2547C LFIB on B

38 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 38 Packet Propagation Across MPLS Network ABC E IP: XLab: 25Lab: 47 IP lookup is performed in FIB, packet is labeled. Label lookup is performed in LFIB, label is switched. Label lookup is performed in LFIB, label is removed. IP: X Ingress LSREgress LSR

39 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 39 Steady State Description After the LSRs have exchanged the labels, LIB, LFIB and FIB data structures are completely populated. Convergence in Packet-mode MPLS

40 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 40 Link Failure Actions Routing protocol neighbors and LDP neighbors are lost after a link failure. Entries are removed from various data structures. 

42 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 42 MPLS Convergence LFIB and labeling information in FIB are rebuilt immediately after the routing protocol convergence, based on labels stored in LIB. 

43 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 43 MPLS Convergence After a Link Failure MPLS convergence in packet-mode MPLS does not impact the overall convergence time. MPLS convergence occurs immediately after the routing protocol convergence, based on labels already stored in LIB.

45 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 45 IP Routing Convergence After Link Recovery IP routing protocols rebuild the IP routing table. FIB and LFIB are also rebuilt, but the label information might be lacking. C C— popC

46 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 46 MPLS Convergence After a Link Recovery Routing protocol convergence optimizes the forwarding path after a link recovery. LIB might not contain the label from the new next-hop by the time the IP convergence is complete. End-to-end MPLS connectivity might be intermittently broken after link recovery. Use MPLS Traffic Engineering for make-before-break recovery.

47 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 47 LDP Session Establishment LDP and TDP use a similar process to establish a session: Hello messages are periodically sent on all interfaces enabled for MPLS. If there is another router on that interface it will respond by trying to establish a session with the source of the hello messages. UDP is used for hello messages. It is targeted at “all routers on this subnet” multicast address (224.0.0.2). TCP is used to establish the session. Both TCP and UDP use well-known LDP port number 646 (711 for TDP).

48 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 48 LDP Neighbor Discovery 1.0.0.1 1.0.0.3 MPLS_A NO_MPLS_C 1.0.0.4 MPLS_D 1.0.0.2 MPLS_B TCP (1.0.0.2:1043  1.0.0.1:646) UDP: Hello (1.0.0.1:1050  224.0.0.2:646) UDP: Hello (1.0.0.4:1033  224.0.0.2:646) UDP: Hello (1.0.0.2:1064  224.0.0.2:646) UDP: Hello (1.0.0.1:1051  224.0.0.2:646) UDP: Hello (1.0.0.4:1034  224.0.0.2:646) UDP: Hello (1.0.0.2:1065  224.0.0.2:646) UDP: Hello (1.0.0.1:1052  224.0.0.2:646) UDP: Hello (1.0.0.4:1035  224.0.0.2:646) UDP: Hello (1.0.0.2:1066  224.0.0.2:646) TCP (1.0.0.4:1065  1.0.0.1:646) TCP (1.0.0.4:1066  1.0.0.2:646) LDP Session is established from the router with higher IP address.

49 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 49 LDP Session Negotiation Peers first exchange initialization messages. The session is ready to exchange label mappings after receiving the first keepalive. 1.0.0.1 MPLS_A 1.0.0.2 MPLS_B Initialization message Establish TCP session Initialization message Keepalive

50 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 50 MPLS Domain Double Lookup Scenario Double lookup is not an optimal way of forwarding labeled packets. A label can be removed one hop earlier. 10.0.0.0/8 L=19 10.0.0.0/8 L=18 10.0.0.0/8 L=17 LFIB 18  19 FIB 10/8  NH, 19 LFIB 17  18 FIB 10/8  NH, 18 LFIB 35  17 FIB 10/8  NH, 17 LFIB 19  untagged FIB 10/8  NH 10.1.1.117 10.1.1.118 10.1.1.119 10.1.1.1 Double lookup is needed: 1.LFIB: remove the label. 2.FIB: forward the IP packet based on IP next- hop address. 10.0.0.0/8

51 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 51 Penultimate Hop Popping MPLS Domain A label is removed on the router before the last hop within an MPLS domain. 10.0.0.0/8 L=pop 10.0.0.0/8 L=18 10.0.0.0/8 L=17 LFIB 18  pop FIB 10/8  NH, 19 LFIB 17  18 FIB 10/8  NH, 18 LFIB 35  17 FIB 10/8  NH, 17 LFIB FIB 10/8  NH 10.1.1.117 10.1.1.118 10.1.1.1 10.1.1.1 One single lookup. 10.0.0.0/8 Pop or implicit null label is adveritsed.

52 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 52 Penultimate Hop Popping Penultimate hop popping optimizes MPLS performace (one less LFIB lookup). PHP does not work on ATM (VPI/VCI cannot be removed). Pop or implicit null label uses value 3 when being advertised to a neighbor.

53 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 53 LDP Messages Discovery messages Used to discover and maintain the presence of new peers Hello packets (UDP) sent to all-routers multicast address Once neighbor is discovered, the LDP session is established over TCP

54 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 54 LDP Messages Session messages Establish, maintain and terminate LDP sessions Advertisement messages Create, modify, delete label mappings Notification messages Error signalling

56 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 56 What Is a VPN? VPN is a set of sites which are allowed to communicate with each other. VPN is defined by a set of administrative policies Policies determine both connectivity and QoS among sites. Policies established by VPN customers. Policies could be implemented completely by VPN service providers. Using BGP/MPLS VPN mechanisms

57 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 57 What Is a VPN? (Cont.) Flexible inter-site connectivity Ranging from complete to partial mesh Sites may be either within the same or in different organizations VPN can be either intranet or extranet Site may be in more than one VPN VPNs may overlap Not all sites have to be connected to the same service provider VPN can span multiple providers

58 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 58 IP VPN Taxonomy Client- Initiated NAS- Initiated IP Tunnel Virtual Circuit Network- Based VPNs Security Appliance RouterFRATM IP VPNs DIALDEDICATED RFC 2547 Virtual Router

59 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 59 MPLS-VPN Terminology Provider Network (P-Network) The backbone under control of a Service Provider Customer Network (C-Network) Network under customer control CE router Customer Edge router. Part of the C-network and interfaces to a PE router

60 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 60 MPLS-VPN Terminology Site Set of (sub)networks part of the C-network and co- located A site is connected to the VPN backbone through one or more PE/CE links PE router Provider Edge router. Part of the P-Network and interfaces to CE routers P router Provider (core) router, without knowledge of VPN

61 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 61 MPLS-VPN Terminology Route-Target 64 bits identifying routers that should receive the route Route Distinguisher Attributes of each route used to uniquely identify prefixes among VPNs (64 bits) – RFC 4364 VRF based (not VPN based) VPN-IPv4 addresses Address including the 64 bits Route Distinguisher and the 32 bits IP address

62 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 62 MPLS-VPN Terminology VRF VPN Routing and Forwarding Instance Routing table and FIB table Populated by routing protocol contexts VPN-Aware network A provider backbone where MPLS-VPN is deployed

63 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 63 MPLS VPN Connection Model A VPN is a collection of sites sharing a common routing information (routing table) A site can be part of different VPNs A VPN has to be seen as a community of interest (or Closed User Group) Multiple Routing/Forwarding instances (VRF) on PE routers

64 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 64 MPLS VPN Connection Model A site belonging to different VPNs may or MAY NOT be used as a transit point between VPNs If two or more VPNs have a common site, address space must be unique among these VPNs Site-1 Site-3 Site-4 Site-2 VPN-A VPN-C VPN-B

65 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 65 MPLS VPN Connection Model The VPN backbone is composed by MPLS LSRs PE routers (edge LSRs) P routers (core LSRs) PE routers are faced to CE routers and distribute VPN information through MP-BGP to other PE routers VPN-IPv4 addresses, Extended Community, Label P routers do not run BGP and do not have any VPN knowledge

66 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 66 MPLS VPN Connection Model VPN_A VPN_B 10.3.0.0 10.1.0.0 11.5.0.0 PP PP PE CE VPN_A VPN_B 10.1.0.0 10.2.0.0 11.6.0.0 CE PE CE VPN_A 10.2.0.0 CE iBGP sessions P routers (LSRs) are in the core of the MPLS cloud PE routers use MPLS with the core and plain IP with CE routers P and PE routers share a common IGP PE router are MP-iBGP fully meshed

67 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 67 MPLS VPN Connection Model PE and CE routers exchange routing information through: EBGP, OSPF, RIPv2, Static routing CE router run standard routing software PE CE CECE Site-2 Site-1 EBGP,OSPF, RIPv2,Static

68 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 68 MPLS VPN Connection Model PE routers maintain separate routing tables The global routing table With all PE and P routes Populated by the VPN backbone IGP (ISIS or OSPF) VRF (VPN Routing and Forwarding) Routing and Forwarding table associated with one or more directly connected sites (CEs) VRF are associated to (sub/virtual/tunnel)interfaces Interfaces may share the same VRF if the connected sites may share the same routing information PE CE CECE Site-2 Site-1 VPN Backbone IGP (OSPF, ISIS) EBGP,OSPF, RIPv2,Static

69 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 69 MPLS VPN Connection Model The routes the PE receives from CE routers are installed in the appropriate VRF The routes the PE receives through the backbone IGP are installed in the global routing table By using separate VRFs, addresses need NOT to be unique among VPNs PE CE CECE Site-2Site-1 VPN Backbone IGP EBGP,OSPF, RIPv2,Static

70 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 70 MPLS VPN Connection Model The Global Routing Table is populated by IGP protocols. In PE routers it may contain the BGP Internet routes (standard BGP-4 routes) BGP-4 (IPv4) routes go into global routing table MP-BGP (VPN-IPv4) routes go into VRFs

71 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 71 MPLS VPN Connection Model PE VPN Backbone IGP iBGP session PE P P P P PE and P routers share a common IGP (ISIS or OSPF) PEs establish MP-iBGP sessions between them PEs use MP-BGP to exchange routing information related to the connected sites and VPNs VPN-IPv4 addresses, Extended Community, Label

72 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 72 MPLS VPN Connection Model PE-1 VPN Backbone IGP PE-2 P P P P PE routers receive IPv4 updates (EBGP, RIPv2, Static…) PE routers translate into VPN-IPv4 Assign a SOO and RT based on configuration Re-write Next-Hop attribute Assign a label based on VRF and/or interface Send MP-iBGP update to all PE neighbors BGP,RIPv2 update for Net1,Next- Hop=CE-1 VPN-IPv4 update: RD:Net1, Next-hop=PE- 1 SOO=Site1, RT=Green, Label=(intCE1) CE-1 Site-2 VPN-IPv4 update is translated into IPv4 address (Net1) put into VRF green since RT=Green and advertised to CE-2 Site-1 CE-2

73 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 73 MPLS VPN Connection Model Receiving PEs translate to IPv4 Insert the route into the VRF identified by the RT attribute (based on PE configuration) The label associated to the VPN-IPv4 address will be set on packet forwarded towards the destination PE-1 VPN Backbone IGP PE-2 P P P P BGP,OSPF, RIPv2 update for Net1 Next-Hop=CE-1 VPN-IPv4 update: RD:Net1, Next-hop=PE- 1 SOO=Site1, RT=Green, Label=(intCE1) CE-1 Site-2 VPN-IPv4 update is translated into IPv4 address (Net1) put into VRF green since RT=Green and advertised to CE-2 Site-1 CE-2

74 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 74 MPLS VPN Connection Model Route distribution to sites is driven by the Site of Origin (SOO) and Route-target attributes BGP Extended Community attribute A route is installed in the site VRF corresponding to the Route-target attribute Driven by PE configuration A PE which connects sites belonging to multiple VPNs will install the route into the site VRF if the Route-target attribute contains one or more VPNs to which the site is associated

75 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 75 MPLS VPN Connection Model MP-BGP Update VPN-IPV4 address Route Distinguisher 64 bits Makes the IPv4 route globally unique RD is configured in the PE for each VRF RD may or may not be related to a site or a VPN IPv4 address (32bits) Extended Community attribute (64 bits) Site of Origin (SOO): identifies the originating site Route-target (RT): identifies the set of sites the route has to be advertised to

76 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 76 MPLS VPN Connection Model MP-BGP Update Any other standard BGP attribute Local Preference MED Next-hop AS_PATH Standard Community... A Label identifying: The outgoing interface The VRF where a lookup has to be done The BGP label will be the second label in the label stack of packets travelling in the core

77 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 77 MPLS VPN Connection Model MP-BGP Update - Extended community BGP extended community attribute Structured, to support multiple applications 64 bits for increased range General form : : Registered AS number : : Registered IP address

78 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 78 MPLS VPN Connection Model MP-BGP Update - Extended community The Extended Community is used to: Identify one or more routers where the route has been originated (site) Site of Origin (SOO) Selects sites which should receive the route Route-Target

79 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 79 MPLS VPN Connection Model MP-BGP Update The Label can be assigned only by the router which address is the Next-Hop attribute PE routers re-write the Next-Hop with their own address (loopback interface address) “Next-Hop-Self” BGP command towards iBGP neighbors Loopback addresses are advertised into the backbone IGP PE addresses used as BGP Next-Hop must be uniquely known in the backbone IGP No summarisation of loopback addresses in the core

80 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 80 MPLS Forwarding Packet forwarding PE and P routers have BGP next-hop reachability through the backbone IGP Labels are distributed through LDP (hop-by-hop) corresponding to BGP Next-Hops Label Stack is used for packet forwarding Top label indicates BGP Next-Hop (interior label) Second level label indicates outgoing interface or VRF (exterior label)

81 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 81 MPLS Forwarding Penultimate Hop Popping PE2 PE1 CE1 CE2 P1 P2 IGP Label(PE2) VPN Label IP packet PE1 receives IP packet Lookup is done on site VRF BGP route with Next-Hop and Label is found BGP next-hop (PE2) is reachable through IGP route with associated label IGP Label(PE2) VPN Label IP packet P routers switch the packets based on the IGP label (label on top of the stack) VPN Label IP packet Penultimate Hop Popping P2 is the penultimate hop for the BGP next- hop P2 remove the top label This has been requested through LDP by PE2 IP packet PE2 receives the packets with the label corresponding to the outgoing interface (VRF) One single lookup Label is popped and packet sent to IP neighbor IP packet CE3

82 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 82 T1 T7 T2 T8 T3 T9 T4 T7 T5 TB T6 TB T7 T8 Packet Forwarding Example 1 VPN_A VPN_B 10.3.0.0 10.1.0.0 11.5.0.0 PP PP PE CE Data, iBGP next hop PE1, iBGP next hop PE2, iBGP next hop PE3, iBGP next hop PE1, iBGP next hop PE4, iBGP next hop PE2, iBGP NH= PE2, T2 T8 Ingress PE receives normal IP Packets from CE router VPN_B FIB PE2 T2 T8PE router does “IP Longest Match” from VPN_B FIB, find iBGP next hop PE2 and impose a stack of labels: exterior Label T2 + Interior Label T8 DataT8T2 VPN_A VPN_B 10.1.0.0 10.2.0.0 11.6.0.0 CE PE1 PE2 CE VPN_A 10.2.0.0 CE

83 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 83 Packet Forwarding Example 1 (cont.) VPN_A VPN_B 10.3.0.0 10.1.0.0 11.5.0.0 PP PP PE CE T7 T8 T9 Ta Tb Tu Tw Tx Ty Tz T8, TA T2Data T8 Data T2Data TB outin / All Subsequent P routers do switch the packet Solely on Interior Label Egress PE router, removes Interior Label Egress PE uses Exterior Label to select which VPN/CE to forward the packet to. Exterior Label is removed and packet routed to CE router VPN_A VPN_B 10.1.0.0 10.2.0.0 11.6.0.0 CE PE1 PE2 CE VPN_A 10.2.0.0 CE T2Data TAT2

84 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 84 Packet Forwarding Example 2 In VPN 12, host 130.130.10.1 sends a packet with destination 130.130.11.3 Customer sites are attached to Provider Edge (PE) routers A & B. 130.130.10.1 130.130.11.3 12 A B

85 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 85 VPN-ID VPN Site Address Provider Edge Router Address VPN Site Label PE Label 12130.130.10.0/24172.68.1.11/322642 12130.130.11.0/24172.68.1.2/32989101... 2. PE router A selects the correct VPN forwarding table based on the links’ VPN ID (12). Packet Forwarding Example 2 (cont.) 12 1. Packet arrives on VPN 12 link on PE router A. A

86 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 86 Packet Forwarding Example 2 (cont.) 130.130.11.3Rest of IP packet VPN-ID VPN Site Address Provider Edge Router Address VPN Site Label PE Label 12130.130.10.0/24172.68.1.11/322642 12130.130.11.0/24172.68.1.2/32989101... 12 A 3. PE router A matches the incoming packet’s destination address with VPN 12’s forwarding table. 989101 4. PE router A adds two labels to the packet: one identifying the destination PE, and one identifying the destination VPN site.

87 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 87 Packet Forwarding Example 2 (cont.) A B 5. Packet is label-switched from PE router A to PE B based on the top label, using normal MPLS. The network core knows nothing about VPNs and sites: it only knows how to get packets from A to B using MPLS.

88 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 88 Packet Forwarding Example 2 (cont.) B 12 6. PE router B identifies the correct site in VPN 12 from the inner label. 130.130.11.3 7. PE router B removes the labels and forwards the IP packet to the correct VPN 12 site.

89 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 89 MPLS VPN mechanisms VRF and Multiple Routing Instances VRF: VPN Routing and Forwarding Instance VRF Routing Protocol Context VRF Routing Tables VRF CEF Forwarding Tables

90 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 90 MPLS VPN mechanisms VRF and Multiple Routing Instances VRF Routing table contains routes which should be available to a particular set of sites Analogous to standard IOS routing table, supports the same set of mechanisms Interfaces (sites) are assigned to VRFs One VRF per interface (sub-interface, tunnel or virtual- template) Possible many interfaces per VRF

91 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 91 MPLS VPN mechanisms VRF and Multiple Routing Instances StaticBGPRIP Routing processe s Routing contexts VRF Routing tables VRF Forwarding tables Routing processes run within specific routing contexts Populate specific VPN routing table and FIBs (VRF) Interfaces are assigned to VRFs

92 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 92 MPLS VPN mechanisms VRF and Multiple Routing Instances Site-1Site-2Site-3Site-4 Logical view Routing view VRF for site-1 Site-1 routes Site-2 routes VRF for site-4 Site-3 routes Site-4 routes VRF for site-2 Site-1 routes Site-2 routes Site-3 routes VRF for site-3 Site-2 routes Site-3 routes Site-4 routes Site-1 Site-3 Site-4 Site-2 VPN-A VPN-C VPN-B PE PP Multihop MP-iBGP

93 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 93 MPLS VPN Topologies VPN_A VPN_B 10.3.0.0 10.1.0.0 11.5.0.0 PP PP PE CE VPN_A VPN_B 10.1.0.0 10.2.0.0 11.6.0.0 CE PE CE VPN_A 10.2.0.0 CE VPN-IPv4 address are propagated together with the associated label in BGP Multiprotocol extension Extended Community attribute (route-target) is associated to each VPN-IPv4 address, to populate the site VRF iBGP sessions

94 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 94 MPLS VPN Topologies VPN sites with optimal intra-VPN routing Each site has full routing knowledge of all other sites (of same VPN) Each CE announces his own address space MP-BGP VPN-IPv4 updates are propagated between PEs Routing is optimal in the backbone Each route has the BGP Next-Hop closest to the destination No site is used as central point for connectivity

95 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 95 MPLS VPN Topologies VPN sites with optimal intra-VPN routing Site-1 VRF for site-1 N1,NH=CE 1 N2,NH=PE 2 N3,NH=PE 3 PE1 PE3 PE2 N1 Site-3 N3 N2 VPN-IPv4 updates exchanged between PEs RD:N1, NH=PE1,Label=IntCE1, RT=Blue RD:N2, NH=PE2,Label=IntCE2, RT=Blue RD:N3, NH=PE3,Label=IntCE3, RT=Blue IntCE 1 IntCE3 N1 NH=CE1 Routing Table on CE1 N1, Local N2, PE1 N3, PE1 EBGP/RIP/Static VRF for site-3 N1,NH=PE 1 N2,NH=PE 2 N3,NH=CE 3 Routing Table on CE3 N1, PE3 N2, PE3 N3, Local N3 NH=CE3 EBGP/RIP/Static Site-2 IntCE2 Routing Table on CE2 N1,NH=PE2 N2,Local N3,NH=PE2 N2,NH=CE2 EBGP/RIP/Static VRF for site-2 N1,NH=PE 1 N2,NH=CE 2 N3,NH=PE 3

96 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 96 MPLS VPN Topologies VPN sites with Hub & Spoke routing One central site has full routing knowledge of all other sites (of same VPN) Hub-Site Other sites will send traffic to Hub-Site for any destination Spoke-Sites Hub-Site is the central transit point between Spoke-Sites Use of central services at Hub-Site

97 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 97 MPLS VPN Topologies VPN sites with Hub & Spoke routing PE2 PE1 PE3 Site-1 N1 N3 VPN-IPv4 updates advertised by PE3 RD:N1, NH=PE3,Label=IntCE3-Spoke, RT=Spoke RD:N2, NH=PE3,Label=IntCE3-Spoke, RT=Spoke RD:N3, NH=PE3,Label=IntCE3-Spoke, RT=Spoke Site-3 Site-2 N2 IntCE3-Spoke VRF (Export RT=Spoke) N1,NH=CE3- Spoke N2,NH=CE3- Spoke N3,NH=CE3- Spoke CE1 CE3-Spoke CE2 CE3-Hub IntCE3-Hub VRF (Import RT=Hub) N1,NH=PE1 N2,NH=PE2 VPN-IPv4 update advertised by PE1 RD:N1, NH=PE1,Label=IntCE1, RT=Hub VPN-IPv4 update advertised by PE2 RD:N2, NH=PE2,Label=IntCE2, RT=Hub IntCE2 VRF (Import RT=Spoke) (Export RT=Hub) N1,NH=PE3 (imported) N2,NH=CE2 (exported) N3,NH=PE3 (imported) IntCE1 VRF (Import RT=Spoke) (Export RT=Hub) N1,NH=CE1 (exported) N2,NH=PE3 (imported) N3,NH=PE3 (imported BGP/RIPv2 Routes are imported/exported into VRFs based on RT value of the VPN-IPv4 updates PE3 uses 2 (sub)interfaces with two different VRFs

98 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 98 MPLS VPN Topologies VPN sites with Hub & Spoke routing PE2 PE1 PE3 Site-1 N1 N3 Site-3 Site-2 N2 IntCE3-Spoke VRF (Export RT=Spoke) N1,NH=CE3- Spoke N2,NH=CE3- Spoke N3,NH=CE3- Spoke CE1 CE3-Spoke CE2 CE3-Hub IntCE3-Hub VRF (Import RT=Hub) N1,NH=PE1 N2,NH=PE2 IntCE2 VRF (Import RT=Spoke) (Export RT=Hub) N1,NH=PE3 (imported) N2,NH=CE2 (exported) N3,NH=PE3 (imported) IntCE1 VRF (Import RT=Spoke) (Export RT=Hub) N1,NH=CE1 (exported) N2,NH=PE3 (imported) N3,NH=PE3 (imported BGP/RIPv2 Traffic from one spoke to another will travel across the hub site Hub site may host central services Security, NAT, centralised Internet access

99 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 99 MPLS VPN Internet Routing In a VPN, sites may need to have Internet connectivity Connectivity to the Internet means: Being able to reach Internet destinations Being able to be reachable from any Internet source The Internet routing table is treated separately In the VPN backbone the Internet routes are in the Global routing table of PE routers Labels are not assigned to external (BGP) routes

100 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 100 MPLS VPN Internet routing VRF specific default route A default route is installed into the site VRF and pointing to a Internet Gateway The default route is NOT part of any VPN A single label is used for packets forwarded according to the default route The label is the IGP label corresponding to the IP address of the Internet gateway Known in the IGP

101 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 101 MPLS VPN Internet routing VRF specific default route PE router originates CE routes for the Internet Customer (site) routes are known in the site VRF Not in the global table The PE/CE interface is NOT known in the global table. However: A static route for customer routes and pointing to the PE/CE interface is installed in the global table This static route is redistributed into BGP-4 global table and advertised to the Internet Gateway The Internet gateway knows customer routes and with the PE address as next-hop

102 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 102 MPLS VPN Internet routing VRF specific default route The Internet Gateway specified in the default route (into the VRF) need NOT to be directly connected Different Internet gateways can be used for different VRFs Using default route for Internet routing does NOT allow any other default route for intra-VPN routing As in any other routing scheme

103 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 103 MPLS VPN Internet routing VRF specific default route PE Internet Site-1 PE-IG Site-2 Network 171.68.0.0/16 Serial0 192.168.1.1 192.168.1.2 ip vrf VPN-A rd 100:1 route-target both 100:1 ! Interface Serial0 ip address 192.168.10.1 255.255.255.0 ip vrf forwarding VPN-A ! Router bgp 100 no bgp default ipv4-unicast network 171.68.0.0 mask 255.255.0.0 neighbor 192.168.1.1 remote 100 neighbor 192.168.1.1 activate neighbor 192.168.1.1 next-hop-self neighbor 192.168.1.1 update-source loopback0 ! address-family ipv4 vrf VPN-A neighbor 192.168.10.2 remote-as 65502 neighbor 192.168.10.2 activate exit-address-family ! address-family vpnv4 neighbor 192.168.1.2 activate exit-address-family ! ip route 171.68.0.0 255.255.0.0 Serial0 ip route vrf VPN-A 0.0.0.0 0.0.0.0 192.168.1.1 global BGP-4 MP-BGP

104 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 104 MPLS VPN Internet routing VRF specific default route PE Internet Site-1 PE-IG Site-2 Network 171.68.0.0/16 Serial0 192.168.1.1 192.168.1.2 Site-2 VRF 0.0.0.0/0 192.168.1.1 (global) Site-1 routes Site-2 routes Global Table and LFIB 192.168.1.1/32 Label=3 192.168.1.2/32 Label=5... IP packet D=cisco.co m Label = 3 IP packet D=cisco.co m

105 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 105 MPLS VPN Internet routing VRF specific default route PE routers need not to hold the Internet table PE routers will use BGP-4 sessions to originate customer routes Packet forwarding is done with a single label identifying the Internet Gateway IP address More labels if Traffic Engineering is used

106 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 106 MPLS VPN Internet Routing Separated (sub)interfaces If CE wishes to receive and announce routes from/to the Internet A dedicated BGP session is used over a separate (sub) interface The PE imports CE routes into the global routing table and advertise them to the Internet The interface is not part of any VPN and does not use any VRF Default route or Internet routes are exported to the CE PE needs to have Internet routing table

107 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 107 MPLS VPN Internet Routing Separated (sub)interfaces The PE uses separate (sub)interfaces with the CE One (sub)interface for VPN routing associated to a VRF Can be a tunnel interface One (sub)interface for Internet routing Associated to the global routing table

108 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 108 MPLS VPN Internet Routing Separated (sub)interfaces PE Internet Site-1 PE-IG Site-2 Network 171.68.0.0/16 Serial0.1 192.168.1.1 192.168.1.2 ip vrf VPN-A rd 100:1 route-target both 100:1 ! Interface Serial0 no ip address ! Interface Serial0.1 ip address 192.168.10.1 255.255.255.0 ip vrf forwarding VPN-A ! Interface Serial0.2 ip address 171.68.10.1 255.255.255.0 ! Router bgp 100 no bgp default ipv4-unicast neighbor 192.168.1.1 remote 100 neighbor 192.168.1.1 activate neighbor 192.168.1.1 next-hop-self neighbor 192.168.1.1 update-source loopback0 neighbor 171.68.10.2 remote 502 ! address-family ipv4 vrf VPN-A neighbor 192.168.10.2 remote-as 502 neighbor 192.168.10.2 activate exit-address-family ! address-family vpnv4 neighbor 192.168.1.2 activate exit-address-family BGP-4 MP-BGP Serial0.2 BGP-4

109 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 109 MPLS VPN Internet Routing Separated (sub)interfaces PE Internet Site-1 PE-IG Site-2 Network 171.68.0.0/16 Serial0.1 192.168.1.1 192.168.1.2 Serial0.2 Serial0.1 Serial0.2 CE routing table Site-2 routes ----> Serial0.1 Internet routes ---> Serial0.2 IP packet D=cisco.co m PE Global Table Internet routes ---> 192.168.1.1 192.168.1.1, Label=3 Label = 3 IP packet D=cisco.co m

110 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 110 Scaling Existing BGP techniques can be used to scale the route distribution: route reflectors Each edge router needs only the information for the VPNs it supports Directly connected VPNs RRs are used to distribute VPN routing information

111 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 111 MPLS-VPN Scaling BGP VPN_A VPN_B 10.3.0.0 10.1.0.0 11.5.0.0 PP PP PE CE RR Route Reflectors VPN_A VPN_B 10.1.0.0 10.2.0.0 11.6.0.0 CE PE1 PE2 CE VPN_A 10.2.0.0 CE Route Reflectors may be partitioned Each RR store routes for a set of VPNs Thus, no BGP router needs to store ALL VPNs information PEs will peer to RRs according to the VPNs they directly connect

112 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 112 MPLS-VPN Scaling BGP updates filtering iBGP full mesh between PEs results in flooding all VPNs routes to all PEs Scaling problems when large amount of routes. In addition PEs need only routes for attached VRFs Therefore each PE will discard any VPN-IPv4 route that hasn’t a route-target configured to be imported in any of the attached VRFs This reduces significantly the amount of information each PE has to store Volume of BGP table is equivalent of volume of attached VRFs (nothing more)

113 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 113 MPLS-VPN Scaling BGP updates filtering Each VRF has an import and export policy configured Policies use route-target attribute (extended community) PE receives MP-iBGP updates for VPN-IPv4 routes If route-target is equal to any of the import values configured in the PE, the update is accepted Otherwise it is silently discarded PE MP-iBGP sessions VRFs for VPNs yellow green VPN-IPv4 update: RD:Net1, Next-hop=PE- X SOO=Site1, RT=Green, Label=XYZ VPN-IPv4 update: RD:Net1, Next-hop=PE- X SOO=Site1, RT=Red, Label=XYZ Import RT=yellow Import RT=green

114 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 114 MPLS-VPN Scaling Route Refresh Policy may change in the PE if VRF modifications are done New VRFs, removal of VRFs However, the PE may not have stored routing information which become useful after a change PE request a re-transmission of updates to neighbors Route-Refresh PE VPN-IPv4 update: RD:Net1, Next-hop=PE- X SOO=Site1, RT=Green, Label=XYZ VPN-IPv4 update: RD:Net1, Next-hop=PE- X SOO=Site1, RT=Red, Label=XYZ Import RT=yellow Import RT=green Import RT=red 1. PE doesn’t have red routes (previously filtered out) 2. PE issue a Route- Refresh to all neighbors in order to ask for re- transmission 3. Neighbors re-send updates and “red” route-target is now accepted

115 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 115 MPLS-VPN Scaling Outbound Route Filters - ORF PE router will discard update with unused route-target Optimization requires these updates NOT to be sent Outbound Route Filter (ORF) allows a router to tell its neighbors which filter to use prior to propagate BGP updates PE VPN-IPv4 update: RD:Net1, Next-hop=PE- X SOO=Site1, RT=Green, Label=XYZ VPN-IPv4 update: RD:Net1, Next-hop=PE- X SOO=Site1, RT=Red, Label=XYZ Import RT=yellow Import RT=green 1. PE doesn’t need red routes 2. PE issue a ORF message to all neighbors in order not to receive red routes 3. Neighbors dynamically configure the outbound filter and send updates accordingly

116 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 116 MPLS VPN - Configuration VPN knowledge is on PE routers PE router have to be configured for VRF and Route Distinguisher VRF import/export policies (based on Route-target) Routing protocol used with CEs MP-BGP between PE routers BGP for Internet routers With other PE routers With CE routers

117 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 117 MPLS VPN - Configuration VRF and Route Distinguisher RD is configured on PE routers (for each VRF) VRFs are associated to RDs in each PE Common (good) practice is to use the same RD for the same VPN in all PEs But not mandatory VRF configuration command ip vrf rd route-target import route-target export

118 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 118 CLI - VRF configuration Site-1Site-2Site-3Site-4 VRF for site-1 (100:1) Site-1 routes Site-2 routes VRF for site-4 (100:4) Site-3 routes Site-4 routes VRF for site-2 (100:2) Site-1 routes Site-2 routes Site-3 routes VRF for site-3 (100:3) Site-2 routes Site-3 routes Site-4 routes PE1 PE2 PP Multihop MP-iBGP ip vrf site1 rd 100:1 route-target export 100:1 route-target import 100:1 ip vrf site2 rd 100:2 route-target export 100:2 route-target import 100:2 route-target import 100:1 route-target export 100:1 ip vrf site1 rd 100:1 route-target export 100:1 route-target import 100:1 ip vrf site2 rd 100:2 route-target export 100:2 route-target import 100:2 route-target import 100:1 route-target export 100:1 ip vrf site3 rd 100:3 route-target export 100:2 route-target import 100:2 route-target import 100:3 route-target export 100:3 ip vrf site-4 rd 100:4 route-target export 100:3 route-target import 100:3 ip vrf site3 rd 100:3 route-target export 100:2 route-target import 100:2 route-target import 100:3 route-target export 100:3 ip vrf site-4 rd 100:4 route-target export 100:3 route-target import 100:3 Site-1 Site-3 Site-4 Site-2 VPN-A VPN-C VPN-B

119 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 119 MPLS VPN - Configuration PE/CE routing protocols PE/CE may use BGP, RIPv2 or Static routes A routing context is used for each VRF Routing contexts are defined within the routing protocol instance Address-family router sub-command Router rip version 2 address-family ipv4 vrf … any common router sub-command …

120 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 120 MPLS VPN - Configuration PE/CE routing protocols BGP uses same “address-family” command Router BGP... address-family ipv4 vrf … any common router BGP sub-command … Static routes are configured per VRF ip route vrf …

121 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 121 MPLS VPN - Configuration PE router commands All show commands are VRF based Show ip route vrf... Show ip protocol vrf Show ip cef … … PING and Telnet commands are VRF based telnet /vrf ping vrf

122 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 122 MPLS VPN - Configuration PE/CE routing protocols Site-1Site-2Site-3Site-4 PE1 PE2 PP Multihop MP-iBGP Site-1 Site-3 Site-4 Site-2 VPN-A VPN-C VPN-B VRF for site-1 (100:1) Site-1 routes Site-2 routes VRF for site-4 (100:4) Site-3 routes Site-4 routes VRF for site-2 (100:2) Site-1 routes Site-2 routes Site-3 routes VRF for site-3 (100:3) Site-2 routes Site-3 routes Site-4 routes ip vrf site3 rd 100:3 route-target export 100:23 route-target import 100:23 route-target import 100:34 route-target export 100:34 ip vrf site-4 rd 100:4 route-target export 100:34 route-target import 100:34 ! interface Serial4/6 ip vrf forwarding site3 ip address 192.168.73.7 255.255.255.0 encapsulation ppp ! interface Serial4/7 ip vrf forwarding site4 ip address 192.168.74.7 255.255.255.0 encapsulation ppp ip vrf site3 rd 100:3 route-target export 100:23 route-target import 100:23 route-target import 100:34 route-target export 100:34 ip vrf site-4 rd 100:4 route-target export 100:34 route-target import 100:34 ! interface Serial4/6 ip vrf forwarding site3 ip address 192.168.73.7 255.255.255.0 encapsulation ppp ! interface Serial4/7 ip vrf forwarding site4 ip address 192.168.74.7 255.255.255.0 encapsulation ppp ip vrf site1 rd 100:1 route-target export 100:12 route-target import 100:12 ip vrf site2 rd 100:2 route-target export 100:12 route-target import 100:12 route-target import 100:23 route-target export 100:23 ! interface Serial3/6 ip vrf forwarding site1 ip address 192.168.61.6 255.255.255.0 encapsulation ppp ! interface Serial3/7 ip vrf forwarding site2 ip address 192.168.62.6 255.255.255.0 encapsulation ppp ip vrf site1 rd 100:1 route-target export 100:12 route-target import 100:12 ip vrf site2 rd 100:2 route-target export 100:12 route-target import 100:12 route-target import 100:23 route-target export 100:23 ! interface Serial3/6 ip vrf forwarding site1 ip address 192.168.61.6 255.255.255.0 encapsulation ppp ! interface Serial3/7 ip vrf forwarding site2 ip address 192.168.62.6 255.255.255.0 encapsulation ppp

123 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 123 MPLS VPN - Configuration PE/CE routing protocols Site-1Site-2Site-3Site-4 PE1 PE2 PP Multihop MP-iBGP Site-1 Site-3 Site-4 Site-2 VPN-A VPN-C VPN-B VRF for site-1 (100:1) Site-1 routes Site-2 routes VRF for site-4 (100:3) Site-3 routes Site-4 routes VRF for site-2 (100:2) Site-1 routes Site-2 routes Site-3 routes VRF for site-3 (100:2) Site-2 routes Site-3 routes Site-4 routes router bgp 100 no bgp default ipv4-unicast neighbor 6.6.6.6 remote-as 100 neighbor 6.6.6.6 update-source Loop0 ! address-family ipv4 vrf site4 neighbor 192.168.74.4 remote-as 65504 neighbor 192.168.74.4 activate exit-address-family ! address-family ipv4 vrf site3 neighbor 192.168.73.3 remote-as 65503 neighbor 192.168.73.3 activate exit-address-family ! address-family vpnv4 neighbor 6.6.6.6 activate neighbor 6.6.6.6 next-hop-self exit-address-family router bgp 100 no bgp default ipv4-unicast neighbor 6.6.6.6 remote-as 100 neighbor 6.6.6.6 update-source Loop0 ! address-family ipv4 vrf site4 neighbor 192.168.74.4 remote-as 65504 neighbor 192.168.74.4 activate exit-address-family ! address-family ipv4 vrf site3 neighbor 192.168.73.3 remote-as 65503 neighbor 192.168.73.3 activate exit-address-family ! address-family vpnv4 neighbor 6.6.6.6 activate neighbor 6.6.6.6 next-hop-self exit-address-family router bgp 100 no bgp default ipv4-unicast neighbor 7.7.7.7 remote-as 100 neighbor 7.7.7.7 update-source Loop0 ! address-family ipv4 vrf site2 neighbor 192.168.62.2 remote-as 65502 neighbor 192.168.62.2 activate exit-address-family ! address-family ipv4 vrf site1 neighbor 192.168.61.1 remote-as 65501 neighbor 192.168.61.1 activate exit-address-family ! address-family vpnv4 neighbor 7.7.7.7 activate neighbor 7.7.7.7 next-hop-self exit-address-family router bgp 100 no bgp default ipv4-unicast neighbor 7.7.7.7 remote-as 100 neighbor 7.7.7.7 update-source Loop0 ! address-family ipv4 vrf site2 neighbor 192.168.62.2 remote-as 65502 neighbor 192.168.62.2 activate exit-address-family ! address-family ipv4 vrf site1 neighbor 192.168.61.1 remote-as 65501 neighbor 192.168.61.1 activate exit-address-family ! address-family vpnv4 neighbor 7.7.7.7 activate neighbor 7.7.7.7 next-hop-self exit-address-family

124 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 124 Summary Supports large scale VPN services Increases value add by the VPN Service Provider Decreases Service Provider’s cost of providing VPN services Mechanisms are general enough to enable VPN Service Provider to support a wide range of VPN customers See RFC2547

125 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 125 Amount of routing peering maintained by CE is O(1) - CE peers only with directly attached PE independent of the total number of sites within a VPN scales to VPNs with large number of sites (100s - 1000s sites per VPN) Point-to-point connections vs BGP/MPLS VPNs: routing peering Mesh of point-to-point connections requires each (virtual) router to maintain O(n) peering (where n is the number of sites) does not scale to VPNs with large number of sites (due to the properties of existing routing protocols) Site All other sites CEPE Routing peering

126 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 126 Amount of configuration changes needed to add a new site (new CE) is O(1): need to configure only the directly attached PE independent of the total number of sites within a VPN Point-to-point connections vs BGP/MPLS VPNs: provisioning All other sites CEPE Config change Mesh of point-to-point connections requires O(n) configuration changes (where n is the number of sites) when adding a new site New Site Config change New Site

128 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 128 show tag-switching tdp parameters router(config)# Displays TDP parameters on the local router. Basic MPLS Monitoring Commands show tag-switching interface show mpls interface 12.1(3)T router(config)# Displays MPLS status on individual interfaces. show tag-switching tdp discovery router(config)# Displays all discovered TDP neighbors.

129 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 129 show tag-switching tdp parameters Router#show tag-switching tdp parameters Protocol version: 1 No tag pool for downstream tag distribution Session hold time: 180 sec; keep alive interval: 60 sec Discovery hello: holdtime: 15 sec; interval: 5 sec Discovery directed hello: holdtime: 180 sec; interval: 5 sec Router#show tag-switching tdp parameters Protocol version: 1 No tag pool for downstream tag distribution Session hold time: 180 sec; keep alive interval: 60 sec Discovery hello: holdtime: 15 sec; interval: 5 sec Discovery directed hello: holdtime: 180 sec; interval: 5 sec

130 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 130 show tag-switching interface Router#show tag-switching interface detail Interface Serial1/0.1: IP tagging enabled TSP Tunnel tagging not enabled Tagging operational MTU = 1500 Interface Serial1/0.2: IP tagging enabled TSP Tunnel tagging not enabled Tagging operational MTU = 1500 Router#show tag-switching interface detail Interface Serial1/0.1: IP tagging enabled TSP Tunnel tagging not enabled Tagging operational MTU = 1500 Interface Serial1/0.2: IP tagging enabled TSP Tunnel tagging not enabled Tagging operational MTU = 1500

131 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 131 show tag-switching tdp discovery Router#show tag-switching tdp discovery Local TDP Identifier: 192.168.3.102:0 TDP Discovery Sources: Interfaces: Serial1/0.1: xmit/recv TDP Id: 192.168.3.101:0 Serial1/0.2: xmit/recv TDP Id: 192.168.3.100:0 Router#show tag-switching tdp discovery Local TDP Identifier: 192.168.3.102:0 TDP Discovery Sources: Interfaces: Serial1/0.1: xmit/recv TDP Id: 192.168.3.101:0 Serial1/0.2: xmit/recv TDP Id: 192.168.3.100:0

132 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 132 show tag-switching tdp neighbor router(config)# Displays individual TDP neighbors. More TDP Monitoring Commands show tag-switching tdp neighbor detail router(config)# Displays more details about TDP neighbors. show tag-switching tdp bindings router(config)# Displays Tag Information Base (TIB).

133 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 133 show tag tdp neighbor Router#show tag-switching tdp neighbors Peer TDP Ident: 192.168.3.100:0; Local TDP Ident 192.168.3.102:0 TCP connection: 192.168.3.100.711 - 192.168.3.102.11000 State: Oper; PIEs sent/rcvd: 55/53; ; Downstream Up time: 00:43:26 TDP discovery sources: Serial1/0.2 Addresses bound to peer TDP Ident: 192.168.3.10 192.168.3.14 192.168.3.100 Router#show tag-switching tdp neighbors Peer TDP Ident: 192.168.3.100:0; Local TDP Ident 192.168.3.102:0 TCP connection: 192.168.3.100.711 - 192.168.3.102.11000 State: Oper; PIEs sent/rcvd: 55/53; ; Downstream Up time: 00:43:26 TDP discovery sources: Serial1/0.2 Addresses bound to peer TDP Ident: 192.168.3.10 192.168.3.14 192.168.3.100

134 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 134 show tag tdp neighbor detail Router#show tag-switching tdp neighbors detail Peer TDP Ident: 192.168.3.100:0; Local TDP Ident 192.168.3.102:0 TCP connection: 192.168.3.100.711 - 192.168.3.102.11000 State: Oper; PIEs sent/rcvd: 55/54; ; Downstream; Last TIB rev sent 26 UID: 1; Up time: 00:44:01 TDP discovery sources: Serial1/0.2; holdtime: 15000 ms, hello interval: 5000 ms Addresses bound to peer TDP Ident: 192.168.3.10 192.168.3.14 192.168.3.100 Peer holdtime: 180000 ms; KA interval: 60000 ms; Peer state: estab Router#show tag-switching tdp neighbors detail Peer TDP Ident: 192.168.3.100:0; Local TDP Ident 192.168.3.102:0 TCP connection: 192.168.3.100.711 - 192.168.3.102.11000 State: Oper; PIEs sent/rcvd: 55/54; ; Downstream; Last TIB rev sent 26 UID: 1; Up time: 00:44:01 TDP discovery sources: Serial1/0.2; holdtime: 15000 ms, hello interval: 5000 ms Addresses bound to peer TDP Ident: 192.168.3.10 192.168.3.14 192.168.3.100 Peer holdtime: 180000 ms; KA interval: 60000 ms; Peer state: estab

135 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 135 show tag tdp bindings Router#show tag tdp bindings tib entry: 192.168.3.1/32, rev 9 local binding: tag: 28 remote binding: tsr: 19.16.3.3:0, tag: 28 tib entry: 192.168.3.2/32, rev 8 local binding: tag: 27 remote binding: tsr: 19.16.3.3:0, tag: 27 tib entry: 192.168.3.3/32, rev 7 local binding: tag: 26 remote binding: tsr: 19.16.3.3:0, tag: imp-null(1) tib entry: 192.168.3.10/32, rev 6 local binding: tag: imp-null(1) remote binding: tsr: 19.16.3.3:0, tag: 26 Router#show tag tdp bindings tib entry: 192.168.3.1/32, rev 9 local binding: tag: 28 remote binding: tsr: 19.16.3.3:0, tag: 28 tib entry: 192.168.3.2/32, rev 8 local binding: tag: 27 remote binding: tsr: 19.16.3.3:0, tag: 27 tib entry: 192.168.3.3/32, rev 7 local binding: tag: 26 remote binding: tsr: 19.16.3.3:0, tag: imp-null(1) tib entry: 192.168.3.10/32, rev 6 local binding: tag: imp-null(1) remote binding: tsr: 19.16.3.3:0, tag: 26

136 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 136 show tag-switching forwarding-table show mpls forwarding-table router(config)# Displays contents of Label Forwarding Information Base. Monitoring Label Switching show ip cef detail router(config)# Displays label(s) attached to a packet during label imposition on edge LSR.

137 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 137 Monitoring Label Switching Monitoring LFIB Router#show tag-switching forwarding-table ? A.B.C.D Destination prefix detail Detailed information interface Match outgoing interface next-hop Match next hop neighbor tags Match tag values tsp-tunnel TSP Tunnel id | Output modifiers Router#show tag-switching forwarding-table ? A.B.C.D Destination prefix detail Detailed information interface Match outgoing interface next-hop Match next hop neighbor tags Match tag values tsp-tunnel TSP Tunnel id | Output modifiers

138 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 138 show tag-switching forwarding-table Router#show tag-switching forwarding-table detail Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 26 Untagged 192.168.3.3/32 0 Se1/0.3 point2point MAC/Encaps=0/0, MTU=1504, Tag Stack{} 27 Pop tag 192.168.3.4/32 0 Se0/0.4 point2point MAC/Encaps=4/4, MTU=1504, Tag Stack{} 20618847 28 29 192.168.3.4/32 0 Se1/0.3 point2point MAC/Encaps=4/8, MTU=1500, Tag Stack{29} 18718847 0001D000 Router#show tag-switching forwarding-table detail Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 26 Untagged 192.168.3.3/32 0 Se1/0.3 point2point MAC/Encaps=0/0, MTU=1504, Tag Stack{} 27 Pop tag 192.168.3.4/32 0 Se0/0.4 point2point MAC/Encaps=4/4, MTU=1504, Tag Stack{} 20618847 28 29 192.168.3.4/32 0 Se1/0.3 point2point MAC/Encaps=4/8, MTU=1500, Tag Stack{29} 18718847 0001D000

139 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 139 show ip cef detail Router#show ip cef 192.168.20.0 detail 192.168.20.0/24, version 23, cached adjacency to Serial1/0.2 0 packets, 0 bytes tag information set local tag: 33 fast tag rewrite with Se1/0.2, point2point, tags imposed: {32} via 192.168.3.10, Serial1/0.2, 0 dependencies next hop 192.168.3.10, Serial1/0.2 valid cached adjacency tag rewrite with Se1/0.2, point2point, tags imposed: {32} Router#show ip cef 192.168.20.0 detail 192.168.20.0/24, version 23, cached adjacency to Serial1/0.2 0 packets, 0 bytes tag information set local tag: 33 fast tag rewrite with Se1/0.2, point2point, tags imposed: {32} via 192.168.3.10, Serial1/0.2, 0 dependencies next hop 192.168.3.10, Serial1/0.2 valid cached adjacency tag rewrite with Se1/0.2, point2point, tags imposed: {32}

140 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 140 debug tag-switching tdp... router(config)# Debugs TDP adjacencies, session establishment, and label bindings exchange. Debugging Label Switching and TDP debug tag-switching tfib... debug mpls lfib … 12.1(3)T router(config)# Debugs Tag Forwarding Information Base events: label creations, removals, rewrites. debug tag-switching packets [ interface ] debug mpls packets [ interface ] 12.1(3)T router(config)# Debugs labeled packets switched by the router. Disables fast or distributed tag switching.

141 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 141 Common Frame-Mode MPLS Symptoms TDP/LDP session does not start. Labels are not allocated or distributed. Packets are not labeled although the labels have been distributed. MPLS intermittently breaks after an interface failure. Large packets are not propagated across the network.

142 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 142 TDP Session Startup Issues: 1/4 Symptom TDP neighbors are not discovered. show tag tdp discovery does not display expected TDP neighbors. Diagnosis MPLS is not enabled on adjacent router. Verification Verify with show tag interface on the adjacent router.

143 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 143 TDP Session Startup Issues: 2/4 Symptom TDP neighbors are not discovered. Diagnosis Label distribution protocol mismatch - TDP on one end, LDP on the other end. Verification Verify with show tag interface detail on both routers.

144 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 144 TDP Session Startup Issues: 3/4 Symptom TDP neighbors are not discovered. Diagnosis Packet filter drops TDP/LDP neighbor discovery packets. Verification Verify access-list presence with show ip interface. Verify access-list contents with show access-list.

145 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 145 TDP Session Startup Issues: 4/4 Symptom TDP neighbors discovered, TDP session is not established. show tdp neighbor does not display a neighbor in Oper state. Diagnosis Connectivity between loopback interfaces is broken - TDP session is usually established between loopback interfaces of adjacent LSRs. Verification Verify connectivity with extended ping command.

146 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 146 Label Allocation Issues Symptom Labels are not allocated for local routes. show tag-switching forwarding-table does not display any labels Diagnosis CEF is not enabled. Verification Verify with show ip cef.

147 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 147 Label Distribution Issues Symptom Labels are allocated, but not distributed. show tag-switching tdp bindings on adjacent LSR does not display labels from this LSR Diagnosis Problems with conditional label distribution. Verification Debug label distribution with debug tag tdp advertisement. Examine the neighbor TDP router IDP with show tag tdp discovery. Verify that the neighbor TDP router ID is matched by the access list specified in tag advertise command.

148 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 148 Packet Labeling Symptom Labels are distributed, packets are not labeled. show interface statistic does not labeled packets being sent Diagnosis CEF is not enabled on input interface (potentially due to conflicting feature being configured). Verification Verify with show cef interface.

149 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 149 show cef interface Router#show cef interface Serial1/0.1 is up (if_number 15) Internet address is 192.168.3.5/30 ICMP redirects are always sent Per packet loadbalancing is disabled IP unicast RPF check is disabled Inbound access list is not set Outbound access list is not set IP policy routing is disabled Interface is marked as point to point interface Hardware idb is Serial1/0 Fast switching type 5, interface type 64 IP CEF switching enabled IP CEF VPN Fast switching turbo vector Input fast flags 0x1000, Output fast flags 0x0 ifindex 3(3) Slot 1 Slot unit 0 VC -1 Transmit limit accumulator 0x0 (0x0) IP MTU 1500 Router#show cef interface Serial1/0.1 is up (if_number 15) Internet address is 192.168.3.5/30 ICMP redirects are always sent Per packet loadbalancing is disabled IP unicast RPF check is disabled Inbound access list is not set Outbound access list is not set IP policy routing is disabled Interface is marked as point to point interface Hardware idb is Serial1/0 Fast switching type 5, interface type 64 IP CEF switching enabled IP CEF VPN Fast switching turbo vector Input fast flags 0x1000, Output fast flags 0x0 ifindex 3(3) Slot 1 Slot unit 0 VC -1 Transmit limit accumulator 0x0 (0x0) IP MTU 1500

150 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 150 Intermittent MPLS Failures after Interface Failure Symptom Overall MPLS connectivity in a router intermittently breaks after an interface failure. Diagnosis IP address of a physical interface is used for TDP/LDP identifier. Configure a loopback interface on the router. Verification Verify local TDP identifier with show tag-switching tdp neighbors.

151 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 151 Packet Propagation Symptom Large packets are not propagated across the network. Extended ping with varying packet sizes fails for packet sizes close to 1500 In some cases, MPLS might work, but MPLS/VPN will fail. Diagnosis Tag MTU issues or switches with no support for jumbo frames in the forwarding path. Verification Trace the forwarding path; identify all LAN segments in the path. Verify Tag MTU setting on routers attached to LAN segments. Check for low-end switches in the transit path.

152 © 2001, Cisco Systems, Inc. All rights reserved. Presentation_ID 152 Summary After completing this lesson, you will be able to perform the following tasks: Describe procedures for monitoring MPLS on IOS platforms. List the debugging commands associated with label switching, LDP and TDP. Identify common configuration or design errors. Use the available debugging commands in real-life troubleshooting scenarios.

1 © 2001, Cisco Systems, Inc. All rights reserved. Session Number Presentation_ID MPLS Introduction.

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1 © 2001, Cisco Systems, Inc. All rights reserved. Session Number Presentation_ID MPLS Introduction.

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