basic mpls configuration

Table of ContentsBasic MPLS Configuration .......................................................................... 1

Frame-Mode MPLS Configuration and Verification ..................................................................................................................... 1Cell-Mode MPLS over ATM Overview, Configuration, and Verification .................................................................................... 15Command Reference .................................................................................................................................................................... 45

Chapter 2. Basic MPLS Configuration

Chapter 2. Basic MPLS ConfigurationMPLS Configuration on Cisco IOS Software By Umesh Lakshman, Lancy Lobo, - CCIE No.4690 ISBN: 1587051990 Publisher: Cisco Press

Prepared for Alex Hannah, Safari ID: [email protected]

Print Publication Date: 2005/10/17 User number: 1727602 2008 Safari Books Online, LLC. This PDF is made available for personal use only during the relevant subscription term, subject to the Safari Terms of Service. Any other userequires prior written consent from the copyright owner. Unauthorized use, reproduction and/or distribution are strictly prohibited and violate applicable laws. All rights reserved.

Chapter 2. Basic MPLS ConfigurationIn the first chapter, you were introduced to the MPLS forwarding model in which labelsare used to forward packets for a certain destination network. You were also provideddetails on frame- and cell-mode MPLS operation.In this chapter, the following topics are covered:

Frame-mode MPLS configuration and verification- Basic frame-mode MPLS configuration and verification- Frame-mode MPLS over RFC 2684 (obsoletes RFC 1483) routed PVC

Cell-mode MPLS over ATM configuration and verification- Basic cell-mode MPLS configuration and verification- Configuring cell-mode MPLS with and without virtual circuit merge (VC-merge)- MPLS over VP tunnels configuration and verification- Configuring MPLS over ATM using BPX ATM switch and 7200 as label switchcontroller (LSC)

Frame-Mode MPLS Configuration and VerificationIn frame mode, MPLS uses a 32-bit label that is inserted between the Layer 2 and Layer 3headers. Layer 2 encapsulations like HDLC, PPP, Frame Relay, and Ethernet are frame-based except for ATM, which can operate either in frame mode or cell mode.

Basic Frame-Mode MPLS Overview, Configuration, and VerificationFigure 2-1 shows a frame-based MPLS provider network providing MPLS services to sitesbelonging to Customer A. The frame-based provider's network consists of routers R1, R2,R3, and R4. R1 and R4 function as Edge Label Switch Routers (LSRs) while R2 and R3serve as LSRs.

Chapter 2. Basic MPLS Configuration Page 1 Return to Table of Contents




Licensed byAlex Hannah

Figure 2-1. Frame-Mode MPLS Provider Network

Figure 2-2 illustrates the configuration flowchart to implement frame-mode MPLS on theprovider network shown in Figure 2-1. The configuration flowchart assumes that IPaddresses are preconfigured where required.

Figure 2-2. Frame-Mode MPLS Configuration Flowchart





Basic Frame-Mode MPLS Configuration StepsThe steps to configure frame-mode MPLS are based on the configuration flowchartoutlined in Figure 2-2. Ensure that IP addresses are configured prior to following thesesteps:

Step 1. Enable CEFCEF is an essential component for label switching and isresponsible for imposition and disposition of labels in an MPLS network.Configure CEF globally on routers R1, R2, R3, and R4 by issuing the ip cef[distributed] command. Ensure that CEF is not disabled on the interface. Ifdisabled, enable CEF on the interface by issuing ip route-cache cef ininterface mode. Use the distributed keyword in the global configurationmode for Cisco platform capable of distributed CEF switching. Example 2-1highlights the configuration to enable CEF on R2. Similarly enable CEF on R1,R3, and R4.Example 2-1. Enable CEF

R2(config)#ip cef distributedR2(config)#do show running-config interface s0/0 | include cef no ip route-cache cefR2(config)#interface s0/0R2(config-if)#ip route-cache cef

Step 2. Configure IGP routing protocolConfigure the IGP routing protocol; inthis case, OSPF. Enable the interfaces on R1, R2, R3, and R4 that are part ofthe provider network in OSPF using networkip-address wild-card-maskareaarea-id command under the OSPF routing process. Example 2-2highlights the OSPF configuration on R2. Similarly configure OSPF on R1, R3,and R4.Example 2-2. Configure IGP Routing Protocol on R2

R2(config)#router ospf 100R2(config)#network 10.10.10.0 0.0.0.255 area 0

Enabling the label distribution protocol is an optional step. TDP is deprecated,and by default, LDP is the label distribution protocol. The command mplslabel protocol {ldp | tdp} is configured only if LDP is not the default labeldistribution protocol or if you are reverting from LDP to TDP protocol or viceversa. The command can be configured in the global as well as in the interfaceconfiguration mode. The interface configuration command will, however,override the global configuration.





Step 3. Assign LDP router IDLDP uses the highest IP address on a loopbackinterface as the LDP router ID. If there is no loopback address defined, thehighest IP address on the router becomes the LDP router ID. To force aninterface to be an LDP router ID, mpls ldp router-idinterface-type number command can be used. The loopback interface address isrecommended because it always remains up. Configure the loopback 0interface on the R2 router to be the LDP router ID as shown in Example 2-3.Repeat the configuration on R1, R3, and R4, assigning the local loopbackinterface as LDP router-id.Example 2-3. Assign LDP Router ID

R2(config)#mpls ldp router-id loopback 0

Step 4. Enable IPv4 MPLS or label forwarding on the interfaceExample2-4 demonstrates the step to enable MPLS forwarding on the interface.Example 2-4. Enable MPLS Forwarding

R2(config)#interface serial 0/0R2(config-if)#mpls ipR2(config)#interface serial 0/1R2(config-if)#mpls ip

Verification of Basic Frame-Mode MPLS OperationThe steps to verify the frame-mode MPLS operation are as follows. All verification stepswere performed on Router R2. Outputs of the commands have been truncated for brevity,and only pertinent lines are depicted:

Step 1. Example 2-5 verifies whether CEF is globally enabled or disabled on the routerby issuing the show ip cef command. As shown in Example 2-5, CEF isdisabled on R2. Example 2-5 shows if CEF is enabled on the router interfaces.Example 2-5. CEF Verification

R2#show ip cef%CEF not runningPrefix Next Hop Interface_____________________________________________________________________R2#show cef interface serial 0/0Serial0/0 is up (if_number 5)





(Output truncated) IP CEF switching enabled IP CEF Fast switching turbo vector(Output Truncated)_____________________________________________________________________R2#show cef interface serial 0/1Serial0/1 is up (if_number 6)(Output Truncated) IP CEF switching enabled IP CEF Fast switching turbo vector

Step 2. Verify MPLS forwarding is enabled on the interfaces by issuing the showmpls interfaces command. Example 2-6 shows that MPLS is enabled on theserial interfaces. The IP column depicts Yes if IP label switching is enabled onthe interface. The Tunnel column is Yes if LSP tunnel labeling (discussed laterin Chapter 9, "MPLS Traffic Engineering") is enabled on the interface, and theOperational column is Yes if packets are labeled on the interface.Example 2-6. MPLS Forwarding Verification

R2#show mpls interfacesInterface IP Tunnel OperationalSerial0/0 Yes (ldp) No YesSerial0/1 Yes (ldp) No Yes

Step 3. Verify the status of the Label Distribution Protocol (LDP) discovery processby issuing show mpls ldp discovery. This command displays neighbordiscovery information for LDP and shows the interfaces over which the LDPdiscovery process is running. Example 2-7 shows that R2 has discovered twoLDP neighbors, 10.10.10.101 (R1) and 10.10.10.103 (R3). The xmit/recv fieldindicates that the interface is transmitting and receiving LDP discovery Hellopackets.Example 2-7. LDP Discovery Verification

R2#show mpls ldp discovery Local LDP Identifier: 10.10.10.102:0 Discovery Sources: Interfaces: Serial0/0 (ldp): xmit/recv LDP Id: 10.10.10.101:0 Serial0/1 (ldp): xmit/recv LDP Id: 10.10.10.103:0





Step 4. Issue show mpls ldp neighbor to verify the status of the LDP neighborsessions. Example 2-8 shows that the LDP session between R2 and R1(10.10.10.101), as well as between R2 and R3 (10.10.10.103), is operational.Downstream indicates that the downstream method of label distribution isbeing used for this LDP session in which the LSR advertises all of its locallyassigned (incoming) labels to its LDP peer (subject to any configured accesslist restrictions).Example 2-8. LDP Neighbor Verification

R2#show mpls ldp neighbor Peer LDP Ident: 10.10.10.101:0; Local LDP Ident 10.10.10.102:0 TCP connection: 10.10.10.101.646 - 10.10.10.102.11012 State: Oper; PIEs sent/rcvd: 26611/26601; Downstream Up time: 2w2d LDP discovery sources: Serial0/0, Src IP addr: 10.10.10.1 Addresses bound to peer LDP Ident: 10.10.10.101 10.10.10.1 Peer LDP Ident: 10.10.10.103:0; Local LDP Ident 10.10.10.102:0 TCP connection: 10.10.10.103.11002 - 10.10.10.102.646 State: Oper; Msgs sent/rcvd: 2374/2374; Downstream Up time: 1d10h LDP discovery sources: Serial0/1, Src IP addr: 10.10.10.6 Addresses bound to peer LDP Ident: 10.10.10.6 10.10.10.103 10.10.10.9

Control and Data Plane Forwarding in Basic Frame-Mode MPLSFigure 2-3 shows the control and data plane forwarding operation in frame-mode MPLS.





Figure 2-3. Frame-Mode MPLS Control and Data Plane Operation

Control Plane Operation in Basic Frame-Mode MPLSFigure 2-3 shows the control plane operation for prefix 10.10.10.101/32 from R1 to R4.The following steps are performed in the label propagation process for prefix10.10.10.101/32:

Step 1. Example 2-9 shows that R1 sends an implicit null or the POP label to R2. Avalue of 3 represents the implicit-null label. R1 propagates the implicit-nulllabel to its penultimate Router R2, which performs the POP function in thedata forwarding from R4 to 10.10.10.101/32. If R1 propagates an explicit-nulllabel, the upstream LSR R2 does not POP the label but assigns a label value of0 and sends a labeled packet to R2.Example 2-9. MPLS Label Bindings on R1

R1#show mpls ldp bindings

tib entry: 10.10.10.101/32, rev 4 local binding: tag: imp-null remote binding: tsr: 10.10.10.102:0, tag: 16

Step 2. Example 2-10 shows R2 assigning an LSP label 16 to 10.10.10.101/32. Thislabel value is propagated to R3. This label value is imposed by R3 in the dataforwarding path (for example, a packet originating from R4 to prefix10.10.10.101/32 on R1).





Example 2-10. Label Allocation and Distribution Verification on R2

R2#show mpls forwarding-tableLocal Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface16 Pop tag 10.10.10.101/32 0 Se0/0 point2point17 Pop tag 10.10.10.8/30 0 Se1/0 point2point18 Pop tag 10.10.10.103/32 0 Se1/0 point2point19 19 10.10.10.104/32 0 Se1/0 point2point

Step 3. Example 2-11 shows that on R3, prefix 10.10.10.101/32 has been assigned alocal label of 17 and an outgoing label of 16. The outgoing label is received fromthe Router R2. The local label of 17 has been propagated during labeldistribution to Router R4. Label 17 is used by R4 in the data forwarding pathfor data destined to prefix 10.10.10.101/32 located on R1 from R4.Example 2-11. Label Allocation and Distribution Verification on R3

R3#show mpls forwarding-tableLocal Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface16 Pop tag 10.10.10.0/30 0 Se0/0 point2point17 16 10.10.10.101/32 0 Se0/0 point2point18 Pop tag 10.10.10.102/32 0 Se0/0 point2point19 Pop tag 10.10.10.104/32 0 Se1/0 point2point

Data Forwarding Operation in Basic Frame-Mode MPLSThe following steps are performed in the data forwarding path from R4 to prefix10.10.10.101/32:

1. As shown in Figure 2-3, R4 imposes label 17 on the data packet originating from R4destined to 10.10.10.101/32.

2. R3 does an LFIB lookup and swaps label 17 for 16 and forwards that data packet toR2.

3. R2 receives the data packet from R3, does a penultimate hop pop function, removeslabel 16, and forwards the data packet to R1.

Final Device Configurations for Basic Frame-Mode MPLSThe pertinent configurations for the devices in the frame-mode MPLS domain are shownin Examples 2-12 through Example 2-15.





Example 2-12. R1 Configuration

hostname R1!ip cef!mpls ldp router-id Loopback0!interface Loopback0 ip address 10.10.10.101 255.255.255.255!interface Serial1/0 description Connection to R2 ip address 10.10.10.1 255.255.255.252 mpls ip!router ospf 100 network 10.10.10.0 0.0.0.255 area 0


hostname R2!ip cef!mpls ldp router-id Loopback0!interface Loopback0 ip address 10.10.10.102 255.255.255.255!interface Serial0/0 description Connection to R1 ip address 10.10.10.2 255.255.255.252mpls label protocol ldpmpls ip!interface Serial0/1 description Connection to R3 ip address 10.10.10.5 255.255.255.252mpls label protocol ldpmpls ip!router ospf 100 network 10.10.10.0 0.0.0.255 area 0


hostname R3!ip cef!mpls label protocol ldp!interface Loopback0 ip address 10.10.10.103 255.255.255.255!interface Serial0/0 description connection to R4 ip address 10.10.10.9 255.255.255.252 mpls ip!interface Serial0/1 description connection to R2





ip address 10.10.10.6 255.255.255.252mpls ip!router ospf 100 network 10.10.10.0 0.0.0.255 area 0


hostname R4!ip cef!mpls label protocol ldp!interface Loopback0 ip address 10.10.10.104 255.255.255.255!interface Serial1/0 Description connection to R3 ip address 10.10.10.10 255.255.255.252 mpls ip!router ospf 100network 10.10.10.0 0.0.0.255 area 0

Frame-Mode MPLS over RFC 2684 Routed PVCFrame-mode MPLS can be implemented over RFC 2684 (previously RFC 1483) routedPVCs. When using PVCs, RFC 2684 specifies the following methods of encapsulation tocarry traffic over ATM AAL5:

VC multiplexing A virtual circuit-based multiplexing method in which each VCcarries one protocol. The user, therefore, defines one PVC per protocol.

LLC/SNAP encapsulation This method multiplexes multiple protocols over asingle ATM virtual circuit.

Figure 2-4 shows the network topology for RFC 2684 routed.





Figure 2-4. Topology: Frame-Mode MPLS Over RFC 2684 Routed PVCs

Figure 2-5 illustrates the flowchart to configure frame-mode MPLS on the providernetwork devices shown in Figure 2-4. The configuration flowchart assumes that IPaddresses are pre-configured where needed.

Figure 2-5. Frame-Mode MPLS Configuration Flowchart





Figure 2-6 shows the flowchart for configuring the ATM PVC route on the LS1010 ATMswitch.

Figure 2-6. Configuration Flowchart for LS1010 ATM Switch

Configuration Steps for Frame-Mode MPLS Over RFC 2684 Routed PVCThe steps to configure RFC 2684 bridged encapsulation over MPLS on R1 and R2 are asfollows. Ensure that IP addresses are preconfigured on R1 and R2, as illustrated in Figure2-4:

Step 1. Follow the steps shown in the "Basic Frame-Mode MPLS ConfigurationSteps" section. These steps are the same for frame-mode MPLS over RFC 2684routed PVC. Follow those steps to configure frame-mode MPLS on R1 and R2:

Step 1. Enable CEFStep 2. Enable IGP routing protocolStep 3. Assign LDP router ID

Step 2. Enable IPv4 MPLS or label forwarding on the interfaceConfigurethe ATM PVCs 2/200 on each of the appropriate subinterfaces on R1 and R2.The encapsulation used on the PVC is ATM aal5snap. Example 2-16 highlightsthe steps to configure ATM PVC.Example 2-16. Configure PVCs on R1 and R2

R1(config)#interface ATM2/0.2 point-to-pointR1(config-subif)# pvc 2/200R1(config-if-atm-vc)# encapsulation aal5snapR1(config-if-atm-vc)# mpls ip_____________________________________________________________________R2(config)#interface ATM2/0.2 point-to-pointR2(config-subif)#pvc 2/200R2(config-if-atm-vc)#encapsulation aal5snapR2(config-if-atm-vc)# mpls ip





Configuration of the LS1010 ATM SwitchConfigure the core ATM switches A1 and A2 to perform VC mapping from one interface toanother. The PVC is a permanent logical connection that you must configure manually,from source to destination, through the ATM network. After it is configured, the ATM network maintains the connection at all times. The configuration of an ingress PVC/interface mapped to an egress PVC/interface needs to be performed only on one of theingress or egress interfaces. Therefore, on ATM switch A1, the configuration is performedon interface ATM1/0/1 mapping PVC 2/200 to interface ATM1/0/0 PVC 2/200. The sameprocess is repeated on ATM switch A2, shown in Example 2-17.Example 2-17. Configure PVC Mapping on A1 and A2

A1(config-if)#interface ATM1/0/1A1(config-if)# description Connection to A2A1(config-if)# atm pvc 2 200 interface ATM1/0/0 2 200_____________________________________________________________________A2(config-if)#interface ATM1/0/1A2(config-if)# description connection to A1A2(config-if)# atm pvc 2 200 interface ATM1/0/0 2 200

Verification Steps for Frame-Mode MPLS Over RFC 2684 Routed PVCThe steps to verify frame-mode MPLS over RFC 2684 (previously RFC 1483) routed PVCare as follows:

Step 1. Verify the operation of MPLS over RFC 2684 by performing a view of the MPLSforwarding information base (LFIB), as shown in Example 2-18.Example 2-18. Verification of LFIB

R1#show mpls forwarding-tableLocal Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface36 Pop tag 10.10.10.104/32 0 AT2/0.2 point2point37 Pop tag 10.10.20.128/30 0 AT2/0.2 point2pointR1#_____________________________________________________________________R2#show mpls forwarding-tableLocal Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface16 Pop tag 10.10.10.101/32 0 AT2/0.2 point2point18 Pop tag 10.10.20.192/30 0 AT2/0.2 point2point

Step 2. As shown in Example 2-19, verify connectivity by issuing pings.





Example 2-19. Verify Connectivity

R1#ping 10.10.10.104Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 10.10.10.101, timeout is 2 seconds:!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 msR4#R2#ping 10.10.10.101Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 10.10.10.101, timeout is 2 seconds:!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 msR4#

Final Device Configuration for Frame-Mode MPLS Over RFC 2684 Routed PVCThe final device configuration for R1, A1, A2, and R2 is shown in Example 2-20 throughExample 2-23.Example 2-20. Configuration of R1

hostname R1!ip cef!interface Loopback0 ip address 10.10.10.101 255.255.255.255!interface Ethernet0 ip address 10.10.20.193 255.255.255.252!interface ATM2/0 no ip address!interface ATM2/0.2 point-to-point description connection to A1 ip address 10.10.20.1 255.255.255.252 mpls ip pvc 2/200 encapsulation aal5snap !router ospf 100 network 10.10.0.0 0.0.0.255 area 0

Example 2-21. A1 Configuration

hostname A1!interface ATM1/0/0 description connection to R1!interface ATM1/0/1 description connection to A2atm pvc 2 200 interface ATM1/0/0 2 200!






hostname A2!interface ATM1/0/0 description connection to R2!interface ATM1/0/1 description connection to A1atm pvc 2 200 interface ATM1/0/0 2 200!


hostname R2!ip cef!interface Loopback0 ip address 10.10.10.104 255.255.255.255!interface Ethernet0 ip address 10.10.20.129 255.255.255.252!interface ATM2/0!interface ATM2/0.2 point-to-point description connection to A2 ip address 10.10.20.2 255.255.255.252mpls ip pvc 2/200 encapsulation aal5snap!router ospf 100 log-adjacency-changes network 10.10.0.0 0.0.255.255 area 0

Cell-Mode MPLS over ATM Overview, Configuration, andVerificationThis section introduces you to cell-mode MPLS over ATM configuration. In MPLS overATM networks, routers are connected to ATM-based provider networks consisting of ATMswitches that forward data based on virtual circuits (VCs) provisioned on the ATMswitches. Cell-mode MPLS uses the virtual path identifier/virtual channel identifier (VPI/VCI) fields in the ATM header as the label value.ATM VCs exist locally (on a link between two adjacent ATM switches or two CPEs) andhave two identifiers: VPI and VCI. These two identifiers are often referred to as a VPI/VCIpair. VPI and VCI numbers are part of ATM cell headers, and they are, therefore, carriedin each ATM cell. Because there are two identifiers, you can have two different types of ATM connections: virtual path and virtual channel. This hierarchy allows aggregation of





the number of virtual channels into a single pipe (virtual path) between sites that need alarge number of VCs.The ATM switch is responsible for switching ATM cells on both the VC and VP. When theATM switch is configured to switch cells on a VC, it has to look at both VPI and VCI fieldsof the cell in order to make a switching decision. Switching is done based on a tablecontaining (port, VPI, VCI) tuplets for the input and output side of the VC. On Cisco IOSATM switches, you can see this table with the show atm vc command. You can alsoconfigure the ATM switch to switch cells based only on the port and VPI number; this iscalled VP switching. For VP switching, the ATM switch uses a table consisting of (port,VPI) pairs for input and output. You can see this table on Cisco IOS ATM switches withthe show atm vp command. When VP switching, the ATM switch uses only the VPI fieldof each ATM cell to make a switching decision, which reduces processing time. The sameholds true for cell header rewrites. In VC switching, both VPI and VCI fields of the cellheader are rewritten and possibly changed. However, in VP switching, only VPI fields canbe changed, and the VCI field remains the same end-to-end.

Basic Cell-Mode MPLS Configuration and VerificationFigure 2-7 shows a basic cell-mode MPLS network in which R1 and R2 perform the ATMEdge LSR function while LS1010 ATM switches A1 and A2 serve as the ATM LSR.

Figure 2-7. Cell-Mode MPLS Network

Basic Cell-Mode MPLS Configuration Flowchart for Edge LSRsFigure 2-8 shows the configuration flowchart to set up basic cell-mode configuration onthe Edge LSR R1 and R2.





Figure 2-8. Basic Cell-Mode MPLS Configuration Flowchart for Edge ATM LSR

Basic Cell-Mode MPLS Configuration Flowchart for LSRsFigure 2-9 shows the configuration flowchart for LSR A1 and A2.





Figure 2-9. Basic Cell-Mode MPLS Configuration Flowchart for ATM LSR

Basic Cell-Mode MPLS Configuration StepsThe configurations for basic cell-mode MPLS are based on the configuration flowchartsoutlined in Figure 2-8 and Figure 2-9. The functions of the Edge ATM LSRs are performedby routers R1 and R2, and the ATM switches A1 and A2 function as ATM LSRs in the cell-mode MPLS domain.Configuration Steps for Edge ATM LSRThis section outlines the steps in the configuration of the Edge ATM LSR R1 for ATM orcell-mode MPLS. Ensure that loopback and interface IP addresses are preconfiguredbefore following the steps:

Step 1. Enable CEFAs shown in Example 2-24, enable CEF globally. Repeat thesame steps on R2.Example 2-24. Enable CEF

R1(config)#ip cef





Step 2. Configure the IGP routing protocolAs shown in Example 2-25,configure OSPF as the IGP routing protocol. Repeat the steps on R2.Example 2-25. Configure IGP for IP Reachability

R1(config)#router ospf 100R1(config-router)#network 10.10.0.0 0.0.0.255 area 0

Step 3. Configure MPLS forwarding on the interfaceCreate an MPLSsubinterface on the ATM link to the connected ATM switch. Enable MPLSforwarding on the ATM subinterface. Example 2-26 demonstrates this step.Example 2-26. Enable MPLS Forwarding

R1(config)#interface atm2/0.1 mplsR1(config-subif)#description Connection to A1R1(config-subif)#ip address 10.10.20.1 255.255.255.252R1(config-subif)#mpls ip_____________________________________________________________________R2(config)#interface atm2/0.1 mplsR2(config-subif)#description Connection to A2R2(config-subif)#ip address 10.10.20.10 255.255.255.252R2(config-subif)#mpls ip

Configuration Steps for ATM LSRThis section demonstrates the steps to configure ATM switches A1 and A2. It is assumedthat CEF is enabled on the switches and IP addresses are configured on the appropriateinterfaces.

Step 1. Configure OSPF as the IGP routing protocolExample 2-27summarizes the step to configure OSPF on A1. Repeat the step on A2.Example 2-27. Configure IGP for IP Connectivity

A1(config)#router ospf 100A1(config-router)#network 10.10.0.0 0.0.255.255 area 0

Step 2. Enable MPLS forwarding on the interfaceEnable MPLS forwardingon the ATM physical interfaces, as shown in Example 2-28.





Example 2-28. Enable MPLS Forwarding

A1(config)#interface atm1/0/0A1(config-if)#mpls ipA1(config)#interface atm 1/0/1A1(config-if)#mpls ip

Note that no configuration has been made on the MPLS ATM subinterfaces on the EdgeATM LSRs or LSRs with regards to the control-vc using the mpls atm control-vccommand. This implies that all the control plane information is propagated and exchangedusing the default control VC VPI/VCI values of 0/32. However, the user can change thecontrol-vc associated on an interface in a cell-mode MPLS network. Changes made to theVPI/VCI values associated to the control-vc on an LSR interface must also be made on theconnected LSR's interface to enable proper exchange of control plane information.Verification of Basic Cell-Mode MPLS ConfigurationThe following steps outline the verification process for cell-mode MPLS operation. Allverifications outlined were performed on Edge ATM LSR R1 and ATM LSR A1:

Step 1. Verify CEF is enabled on the router interfaces on Edge LSR R1, as shown inExample 2-29.Example 2-29. Verify CEF Is Enabled on the Interfaces

R1#show cef interface atm2/0ATM2/0 is up (if_number 12)

IP CEF switching enabled IP Feature Fast switching turbo vectorIP Feature CEF switching turbo vector

Step 2. As shown in Example 2-30, verify that MPLS forwarding is enabled on theappropriate interfaces on R1 and A1.Example 2-30. Verify MPLS Forwarding

R1#show mpls interfacesInterface IP Tunnel OperationalATM2/0.1 Yes No Yes (ATM tagging)_____________________________________________________________________A1#show mpls interfacesInterface IP Tunnel OperationalATM1/0/0 Yes No Yes (ATM tagging)ATM1/0/1 Yes No Yes (ATM tagging)





Step 3. Verify the status of the LDP discovery process by issuing show mpls ldpdiscovery. This command displays neighbor discovery information for LDPand shows the interfaces over which the LDP discovery process is running.Example 2-31 shows neighbor discovery information and interfaces whereLDP is running on R1 and A1. The xmit/recv field indicates that the interfaceis transmitting and receiving LDP discovery Hello packets.Example 2-31. Verify MPLS LDP Discovery

R1#show mpls ldp discoveryLocal LDP Identifier: 10.10.10.101:0LDP Discovery Sources: Interfaces: ATM2/0.1: xmit/recv LDP Id: 10.10.20.101:1; IP addr: 10.10.20.2 LDP Id: 10.10.20.102:2; IP addr: 10.10.20.6_____________________________________________________________________A1#show mpls ldp discoveryLocal LDP Identifier: 10.10.20.101:0LDP Discovery Sources: Interfaces: ATM1/0/0: xmit/recv LDP Id: 10.10.10.101:1; IP addr: 10.10.20.1 ATM1/0/1: xmit/recv

Step 4. Issue show mpls ldp neighbor to verify the status of LDP neighborsessions. Example 2-32 shows that the LDP session between R1 and A1 isoperational. Downstream on demand on R1 indicates the downstream ondemand method of label distribution is used for the LDP session between R1and A1 in which the LSR (R1) advertises its locally assigned (incoming) labelsto its LDP peer, A1, only when A1 requests them.Example 2-32. LDP Distribution Protocol Neighbor Verification

R1#show mpls ldp neighborPeer LDP Ident: 10.10.20.101:1; Local LDP Ident 10.10.10.101:1 TCP connection: 10.10.20.2.38767 - 10.10.20.1.646 State: Oper; PIEs sent/rcvd: 371/366; ; Downstream on demand Up time: 05:04:40 LDP discovery sources: ATM2/0.1_____________________________________________________________________A1#show mpls ldp neighborPeer LDP Ident: 10.10.20.102:2; Local LDP Ident 10.10.20.101:2 TCP connection: 10.10.20.6.11002 - 10.10.20.5.646 State: Oper; PIEs sent/rcvd: 28096/28083; ; Downstream on demand Up time: 2w3d





LDP discovery sources: ATM1/0/1Peer LDP Ident: 10.10.10.101:1; Local LDP Ident 10.10.20.101:1 TCP connection: 10.10.20.1.646 - 10.10.20.2.38767 State: Oper; PIEs sent/rcvd: 365/369; ; Downstream on demand Up time: 05:03:28 LDP discovery sources: ATM1/0/0

Step 5. Verify OSPF routing table on R4, as shown in Example 2-33.Example 2-33. Verify OSPF Routing

R1#show ip route ospf

10.0.0.0/8 is variably subnetted, 7 subnets, 2 masksO 10.10.20.4/30 [110/2] via 10.10.20.2, 05:51:42, ATM2/0.1O 10.10.20.8/30 [110/3] via 10.10.20.2, 05:51:42, ATM2/0.1O 10.10.10.104/32 [110/4] via 10.10.20.2, 05:51:42, ATM2/0.1O 10.10.20.101/32 [110/2] via 10.10.20.2, 05:51:42, ATM2/0.1O 10.10.20.102/32 [110/3] via 10.10.20.2, 05:51:42, ATM2/0.1

Step 6. Issue ping to 10.10.10.104 from R1 to ensure reachability, as displayed inExample 2-34.Example 2-34. Verify Reachability

R1#ping 10.10.10.104Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 10.10.10.104, timeout is 2 seconds:!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

Control and Data Forwarding Operation in Basic Cell-Mode MPLS ConfigurationFigure 2-10 shows the control and data plane forwarding operation in cell-mode MPLS.





Figure 2-10. Control and Data Plane Operation in Cell-Mode MPLS

Control Plane Operation in Basic Cell-Mode MPLS ConfigurationThe control plane operation shows the label propagation for prefix 10.10.10.101/32 fromR1 to R4. The following steps are performed in the label propagation process for prefix10.10.10.101/32:

Step 1. Edge ATM LSR R4 requests a label for the 10.10.10.101/32 prefix using theLDP label mapping request from its downstream neighbor, ATM LSR A2. A2requests a label for the 10.10.10.101/32 prefix using the LDP label mappingrequest from its downstream neighbor, ATM LSR A1. A1 in turn requests alabel for the 10.10.10.101/32 prefix using the LDP label mapping request fromits downstream neighbor, Edge ATM LSR R1. Edge ATM LSR R1 allocates alabel to 10.10.10.101/32, which corresponds to its inbound VPI/VCI value1/34, modifies the entry in the LFIB corresponding to 10.10.10.101/32, andsends it to A1 using an LDP reply. Example 2-35 shows the output of showmpls atm-ldp bindings.Example 2-35. Label Allocation and Distribution Verification on R1

R1#show mpls forwarding-tableLocal Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface18 1/35 10.10.10.104/32 0 AT2/0.1 point2point25 1/37 10.10.20.8/30 0 AT2/0.1 point2point26 1/36 10.10.20.4/30 0 AT2/0.1 point2point27 1/38 10.10.20.101/32 0 AT2/0.1 point2point





28 1/39 10.10.20.102/32 0 AT2/0.1 point2point_____________________________________________________________________R1#show mpls atm-ldp bindings Destination: 10.10.10.104/32 Headend Router ATM2/0.1 (3 hops) 1/35 Active, VCD=19 Destination: 10.10.20.4/30 Headend Router ATM2/0.1 (1 hop) 1/36 Active, VCD=13 Destination: 10.10.20.8/30 Headend Router ATM2/0.1 (2 hops) 1/37 Active, VCD=15 Destination: 10.10.20.101/32 Headend Router ATM2/0.1 (1 hop) 1/38 Active, VCD=14 Destination: 10.10.20.102/32 Headend Router ATM2/0.1 (2 hops) 1/39 Active, VCD=16 Destination: 10.10.10.101/32 Tailend Router ATM2/0.1 1/34 Active, VCD=18

Step 2. A1 uses the VPI/VCI 1/34 received from R1 as its outbound VPI/VCI value,allocates a free VC that is mapped to the local inbound VPI/VCI 1/45, andmodifies the LFIB entry for 10.10.10.101/32. A1 then sends VPI/VCI value1/45 to A2 via an LDP reply. Example 2-36 shows the output of show mplsatm-ldp bindings. ATM LSR A1 prefix 10.10.10.104/32 has been assigneda local tag of 1/35 and an outgoing tag of 1/43. The outgoing tag is receivedfrom the downstream ATM LSR A2. During label distribution, the local tag of1/35 has been propagated upstream to Router R1, which functions as theoutgoing tag for the specific prefix 10.10.10.104/32 on R1.Example 2-36. Label Allocation and Distribution Verification on A1

A1#show mpls atm-ldp bindings Destination: 10.10.20.101/32 Tailend Switch ATM1/0/1 1/42 Active -> Terminating Active Tailend Switch ATM1/0/0 1/38 Active -> Terminating Active Destination: 10.10.20.0/30 Tailend Switch ATM1/0/1 1/43 Active -> Terminating Active Destination: 10.10.10.104/32 Transit ATM1/0/0 1/35 Active -> ATM1/0/1 1/43 Active Destination: 10.10.20.4/30 Tailend Switch ATM1/0/0 1/36 Active -> Terminating Active Destination: 10.10.20.8/30 Transit ATM1/0/0 1/37 Active -> ATM1/0/1 1/44 Active Destination: 10.10.20.102/32 Transit ATM1/0/0 1/39 Active -> ATM1/0/1 1/45 Active Destination: 10.10.10.101/32 Transit ATM1/0/1 1/45 Active -> ATM1/0/0 1/34 Active

Step 3. A2 uses the VPI/VCI 1/45 received from A1 as its outbound VPI/VCI value,allocates a free VC that is mapped to the local inbound VPI/VCI 1/44, andmodifies the LFIB entry for 10.10.10.101/32. A2 then sends VPI/VCI value1/44 to R2 via an LDP reply. Example 2-37 shows the output of show mpls





atm-ldp bindings. As shown in Example 2-37, ATM LSR A2 prefix10.10.10.104/32 has been assigned a local tag of 1/43 and an outgoing tag of1/35. The outgoing tag is received from the downstream Router R4. The localtag of 1/43 is propagated upstream to ATM LSR A1 and functions as the next-hop tag or outgoing tag for prefix 10.10.10.104/32 on ATM LSR A1.Example 2-37. Label Allocation and Distribution Verification on A2

A2#show mpls atm-ldp bindings Destination: 10.10.20.4/30 Tailend Switch ATM1/0/0 1/33 Active -> Terminating Active Destination: 10.10.20.101/32 Transit ATM1/0/0 1/34 Active -> ATM1/0/1 1/42 Active Destination: 10.10.20.102/32 Tailend Switch ATM1/0/0 1/35 Active -> Terminating Active Tailend Switch ATM1/0/1 1/45 Active -> Terminating Active Destination: 10.10.20.0/30 Transit ATM1/0/0 1/36 Active -> ATM1/0/1 1/43 Active Destination: 10.10.10.104/32 Transit ATM1/0/1 1/43 Active -> ATM1/0/0 1/35 Active Destination: 10.10.20.8/30 Tailend Switch ATM1/0/1 1/44 Active -> Terminating Active Destination: 10.10.10.101/32 Transit ATM1/0/0 1/44 Active -> ATM1/0/1 1/45 Active

Step 4. Edge ATM LSR R2 uses VPI/VCI value 1/44 received from A2 as its outboundVPI/VCI value and modifies the entry in the LFIB. Example 2-38 shows theoutput of show mpls atm-ldp bindings. As shown in Example 2-38 onEdge ATM LSR R2, the mpls atm-ldp bindings show the local tag of 1/35assigned to prefix 10.10.10.104/32. This local tag is propagated upstream toATM LSR A2 and functions as the next-hop tag or outgoing tag for prefix10.10.10.104/32 on A2.Example 2-38. Label Allocation and Distribution Verification on R2

R2#show mpls forwarding-tableLocal Outgoing Prefix Bytes tag Outgoing Next Hoptag tag or VC or Tunnel Id switched interface16 1/36 10.10.20.0/30 0 AT2/0.1 point2point17 1/33 10.10.20.4/30 0 AT2/0.1 point2point18 1/44 10.10.10.101/32 0 AT2/0.1 point2point19 1/34 10.10.20.101/32 0 AT2/0.1 point2point20 1/35 10.10.20.102/32 0 AT2/0.1 point2point_____________________________________________________________________R2#show mpls atm-ldp bindings Destination: 10.10.20.0/30 Headend Router ATM2/0.1 (2 hops) 1/36 Active, VCD=16 Destination: 10.10.20.4/30 Headend Router ATM2/0.1 (1 hop) 1/33 Active, VCD=13





Destination: 10.10.20.101/32 Headend Router ATM2/0.1 (2 hops) 1/34 Active, VCD=15 Destination: 10.10.20.102/32 Headend Router ATM2/0.1 (1 hop) 1/35 Active, VCD=14 Destination: 10.10.10.101/32 Headend Router ATM2/0.1 (3 hops) 1/44 Active, VCD=18 Destination: 10.10.10.104/32 Tailend Router ATM2/0.1 1/35 Active, VCD=14

Data Forwarding Operation in Basic Cell-Mode MPLS ConfigurationThe following steps are performed in the data forwarding path from R4 to prefix10.10.10.101/32:

Step 1. R4 imposes label 1/44 on the AAL5 cell originating from R4 and destined to10.10.10.101/32.

Step 2. A2 does an LFIB lookup and swaps label 1/44 with 1/45 and forwards thatAAL5 cell to A1.

Step 3. A1 receives the data packet from A2, does an LFIB lookup, swaps label 1/45with 1/34, and forwards that AAL5 cell to R1. Penultimate hop popping is notsupported on ATM devices because the label is part of the ATM cell payloadand cannot be removed by ATM switching hardware. Therefore, A1, which isan ATM device, does not perform any penultimate hop popping function.

Final Device Configurations for Basic Cell-Mode MPLSExample 2-39 through Example 2-42 outline the pertinent configurations for all thedevices in the cell-mode MPLS domain.Example 2-39. R1 Configuration

hostname R1!ip cef!interface Loopback0 ip address 10.10.10.101 255.255.255.255!interface ATM2/0!interface ATM2/0.1 mpls description Connection to A1 ip address 10.10.20.1 255.255.255.252 mpls ip!router ospf 100 log-adjacency-changes network 10.10.0.0 0.0.255.255 area 0






hostname A1!interface ATM1/0/0description Connection to R1 ip address 10.10.20.2 255.255.255.252mpls ip!interface ATM1/0/1 description Connection to A2 ip address 10.10.20.5 255.255.255.252mpls ip!router ospf 100 network 10.10.0.0 0.0.255.255 area 0


hostname A2!interface ATM1/0/0 description connection to R2 ip address 10.10.20.9 255.255.255.252mpls ip!interface ATM1/0/1 description connection to A1 ip address 10.10.20.6 255.255.255.252mpls ip!router ospf 100 network 10.10.0.0 0.0.255.255 area 0!


hostname R2!ip cef!interface Loopback0 ip address 10.10.10.104 255.255.255.255!interface ATM2/0!interface ATM2/0.1 mpls description connection to A2 ip address 10.10.20.10 255.255.255.252 mpls ip!router ospf 100 log-adjacency-changes network 10.10.0.0 0.0.255.255 area 0

Configuring Cell-Mode MPLS with VC-MergeThe VC-merge feature in cell-mode MPLS allows an ATM LSR to aggregate multipleincoming flows with the same destination address into a single outgoing flow. Therefore,





when two Edge LSRs are sending packets to the same destination, the ingress labelmapping to the two Edge LSRs are mapped to a single outgoing label. The number of VCsrequired for label switching is greatly reduced as the ATM switch maintains just oneoutgoing VC label for each destination prefix. VC-merge reduces the label space that needsto be maintained by sharing labels for flows toward the same FEC or prefix.Figure 2-11 shows a cell-mode MPLS network. This is the same as the network shown inFigure 2-10 except the new Router R3 is added, which is connected to A1. Edge LSRs R1and R3 share the same label space for the same destination prefixes on Edge ATM LSRR2.

Figure 2-11. Cell-Mode MPLS Topology for VC-Merge

Configuration Flowchart for Cell-Mode MPLS with VC-MergeThe configuration flowchart for Edge ATM LSR for cell-mode MPLS with VC-mergeremains the same as what was shown for basic cell-mode MPLS (refer to Figure 2-8). Theonly difference in the basic cell-mode MPLS configuration block and cell-mode MPLS withVC-merge for ATM LSR is the inclusion of the command shown in Example 2-43.Example 2-43. Enabling ATM VC-Merge

A1(config)#mpls ldp atm vc-merge

Depending upon the hardware, the ATM VC-merge capability is enabled by default;otherwise, this feature is disabled. Please check Cisco Documentation at cisco.com.





Configuration Steps for Cell-Mode MPLS with VC-Merge on Edge ATM LSRThe configuration steps for cell-mode MPLS with VC-merge on Edge ATM LSR are thesame as what was shown earlier in section "Configuration Steps for Edge ATM LSR."Configuration Steps for Cell-Mode MPLS with VC-Merge on ATM LSRThe configuration steps for cell-mode MPLS with VC-merge on ATM LSR are the same asthose shown in the section "Configuration Steps for ATM LSR," except that A1 is enabledwith the VC-merge command mpls ldp atm vc-merge.Final Configuration for Devices in Cell-Mode MPLS with VC-MergeThe configurations for R1, R2, and A2 remain the same as what was shown in thesection "Final Device Configurations for Basic Cell-Mode MPLS." The configurations forR3 and A1 are shown in Example 2-44 and Example 2-45. Note that the configuration forA1 does not depict the mpls ldp atm vc-merge command, which implies that the ATMLSR A1 supports VC-merge functionality by default.Example 2-44. R3 Configuration (Truncated)

hostname R3!ip cef!interface Loopback0 ip address 10.10.10.105 255.255.255.255!interface ATM2/0!interface ATM2/0.1 mpls description connection to A1 ip address 10.10.20.13 255.255.255.252 mpls ip!router ospf 100network 10.10.0.0 0.0.255.255 area 0

Example 2-45. A1 Configuration (Truncated)

hostname A1!interface Loopback0 ip address 10.10.20.101 255.255.255.255!interface ATM1/0/0 description Connection to R1 ip address 10.10.20.2 255.255.255.252mpls ip!interface ATM1/0/1 description Connection to A2 ip address 10.10.20.5 255.255.255.252 mpls ip!interface ATM1/0/2 description connection to R5 ip address 10.10.20.14 255.255.255.252mpls ip





!router ospf 100 network 10.10.0.0 0.0.255.255 area 0

Verification Steps for Cell-Mode MPLS with VC-Merge on ATM LSRThe following steps outline the verification procedure for cell-mode MPLS over ATMimplementation with VC-merge on the ATM LSRs:

Step 1. Verify if ATM VC-merge is enabled on the ATM LSR by issuing the show mplsatm-ldp capability command on the ATM LSR. The output of this commandis shown in Example 2-46.Example 2-46. ATM VC-Merge Capability

A1#show mpls atm-ldp capability

VPI VCI Alloc Odd/Even VC-MergeATM1/0/0 Range Range Scheme Scheme IN OUT Negotiated [1 - 1] [33 - 16383] UNIDIR - - Local [1 - 1] [33 - 16383] UNIDIR EN EN Peer [1 - 1] [33 - 65530] UNIDIR - -

VPI VCI Alloc Odd/Even VC-MergeATM1/0/1 Range Range Scheme Scheme IN OUT Negotiated [1 - 1] [33 - 16383] UNIDIR - - Local [1 - 1] [33 - 16383] UNIDIR EN EN Peer [1 - 1] [33 - 16383] UNIDIR

Step 2. When VC-merge is implemented on A1, destinations reachable by R1 and R3via A1 are provided the same next-hop labels. When a lookup of the labelbindings for prefixes on ATM LSR A1 is performed, the same outgoing labelis used for two different incoming labels from two different flows that map tothe same destination prefix. This is shown in Example 2-47. The ATM LSR A1maps two incoming labels, 1/35 and 1/34, from Edge ATM LSRs R1 and R5,respectively, to the same outgoing label 1/43 for the destination prefix10.10.10.104/32 located on R1.Example 2-47. A1 VC-Merge Verification

A1#show mpls atm-ldp bindings 10.10.10.104 255.255.255.255Destination: 10.10.10.104/32 Transit ATM1/0/0 1/35 Active -> ATM1/0/1 1/43 Active Transit ATM1/0/2 1/34 Active -> ATM1/0/1 1/43 Active





Configuring MPLS Over ATM Without VC-MergeIn MPLS over ATM without VC-merge, each path (with the same ingress router and sameForwarding Equivalent Class [FEC]) consumes one label VC on each interface along thepath. This results in unnecessary exhaustion of the already scarce label space.The network topology remains the same as what was shown in the section "ConfiguringCell-Mode MPLS with VC-Merge." All configurations remain the same except, as shownin Figure 2-11, where VC-merge is disabled on A1. Example 2-48 highlights theconfiguration to disable VC-merge.Example 2-48. Disabling VC-Merge on A1

A1(config)#no mpls ldp atm vc-merge

Verify MPLS Over ATM Without VC-MergeAs shown in Example 2-49, when VC-merge is disabled on ATM LSR A1, flows to the samedestination are assigned different outgoing VC labels. show mpls atm-ldp bindings onA1 shows two different outgoing labels, 1/33 and 1/36, are assigned to the data flows fromR3 and R1, respectively, to destination prefix 10.10.10.104/32. Because VC-merge is notused, one VC is allocated per route as determined by the prefix in the routing table.Example 2-49. A1: Disabled VC-Merge Verification

A1#show mpls atm-ldp bindings 10.10.10.104 255.255.255.255Destination: 10.10.10.104/32 Transit ATM1/0/2 1/34 Active -> ATM1/0/1 1/33 Active Transit ATM1/0/0 1/33 Active -> ATM1/0/1 1/36 Active

MPLS Over VP Tunnels Configuration and VerificationA VP tunnel is a method of linking two private ATM networks across a public network thatdoes not support SVCs. The VP tunnel provides a permanent path through the publicnetwork. VP tunnels are multiplexing/demultiplexing multiple VCs from multipleinterfaces, or from the same interface, to the VP tunnel interface. When multiplexing, itchanges the VPI field of VCs that goes through the VP to the same as the VPI number onthe VPs. VCI numbers, though, can be arbitrary. However, for specific VCs, the VCInumbers on both VP tunnel interfaces (originating and terminating) need to be the same.In this section, you configure VP tunnels on the ATM switches to carry label informationfor MPLS over ATM VP tunnels. Figure 2-12 shows an MPLS network using VP tunnels.





Figure 2-12. MPLS Over VP Tunnels Topology

Configuration Flowchart for MPLS over VP Tunnels on Edge ATM LSRThe basic configuration flowchart for MPLS over VP tunnel is the same as what was shownin the section "Basic Cell-Mode MPLS Configuration and Verification" (refer to Figure2-8).Configuration Flowchart for Creating an ATM PVP on ATM SwitchThe configuration flowchart for creating an ATM PVP is shown in Figure 2-13.

Figure 2-13. Configuration Flowchart for MPLS Over VP Tunnel on ATM LSR

Configuration Steps for MPLS over VP TunnelsEnsure necessary IP addresses are configured prior to following these steps. The steps toconfigure MPLS over VP tunnels are as follows:

Step 1. A VP connection is like a bundle of VCs, transporting all cells with a commonVPI, rather than a specific VPI and VCI. A PVP is a permanent VP (like PVC).Example 2-50 shows how to configure the internal cross-connect (within theswitch router) PVP on switch A1 between interface 1/0/0, VPI = 2 and interface1/0/1, VPI = 2, and switch A2 between interface 1/0/0, VPI = 2 and interface1/0/1, VPI = 2.





Example 2-50. Configure VP Tunnels on ATM Switches

A1(config)#interface ATM1/0/1A1(config-if)# description Connection to A2A1(config-if)# no ip addressA1(config-if)# atm pvp 2 interface ATM1/0/0 2_____________________________________________________________________A2(config)#interface ATM1/0/1A2(config-if)# description connection to A1A2(config-if)# no ip addressA2(config-if)# atm pvp 2 interface ATM1/0/0 2

Step 2. Configure the VP tunnel using mpls atm vp-tunnelvpivc-range {start-of-vci-range-end-of-vci-range} under the MPLS ATM subinterface. EnableMPLS on the created subinterface, as shown in Example 2-51.Example 2-51. Configure VP Tunnel on ATM MPLS Subinterface

R1(config)#interface ATM2/0.1 mplsR1(config-subif)# description Connection to A1R1(config-subif)# ip address 10.10.20.1 255.255.255.252R1(config-subif)# mpls atm vp-tunnel 2 vci-range 33-65535R1(config-subif)#mpls ip_____________________________________________________________________R2(config)#interface ATM2/0.1 mplsR2(config-subif)# description connection to A2R2(config-subif)# ip address 10.10.20.2 255.255.255.252R2(config-subif)# mpls atm vp-tunnel 2 vci-range 33-65535R2(config-subif)#mpls ip

Step 3. Configure IGP for IP connectivity across the VP tunnel on R1 and R2, as shownin Example 2-52.Example 2-52. Configure IGP

R1(config)#router ospf 100R1(config-router)# network 10.10.0.0 0.0.255.255 area 0

Verification Steps for MPLS over VP TunnelsThe steps to verify MPLS over VP tunnels are as follows:

Step 1. Verify operation of PVP on the ATM switches, as shown in Example 2-53.





Example 2-53. Verify PVP Status

A1#show atm vpInterface VPI Type X-Interface X-VPI StatusATM1/0/0 2 PVP ATM1/0/1 2 UPATM1/0/1 2 PVP ATM1/0/0 2 UP_____________________________________________________________________A2#show atm vpInterface VPI Type X-Interface X-VPI StatusATM1/0/0 2 PVP ATM1/0/1 2 UPATM1/0/1 2 PVP ATM1/0/0 2 UP

Step 2. Verify OSPF routes on R1 by issuing show ip route ospf. Example 2-54shows the networks received on R1 from R2.Example 2-54. Verify OSPF Routes

R1#show ip route ospf 10.0.0.0/8 is variably subnetted, 7 subnets, 2 masksO 10.10.20.2/32 [110/1] via 10.10.20.2, 00:12:25, ATM2/0.1O 10.10.10.104/32 [110/2] via 10.10.20.2, 00:12:25, ATM2/0.1O 10.10.20.128/30 [110/11] via 10.10.20.2, 00:12:25, ATM2/0.1

Step 3. Verify connectivity across the VP tunnel using the ping command, as shownin Example 2-55.Example 2-55. Verify Connectivity Using Ping

R1#ping ip 10.10.20.129 source 10.10.20.193Type escape sequence to abort.Sending 5, 100-byte ICMP Echos to 10.10.20.129, timeout is 2 seconds:Packet sent with a source address of 10.10.20.193!!!!!Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

Final Device Configurations for MPLS over VP TunnelsThe final device configuration for R1, A1, A2, and R2 is shown in Example 2-56 throughExample 2-59.Example 2-56. R1 Configuration

hostname R1!ip cef!interface Loopback0 ip address 10.10.10.101 255.255.255.255!





interface Ethernet0ip address 10.10.20.193 255.255.255.252!interface ATM2/0!interface ATM2/0.1 mpls description Connection to A1 ip address 10.10.20.1 255.255.255.252 mpls ip mpls atm vp-tunnel 2 vci-range 33-65535!router ospf 100

network 10.10.0.0 0.0.255.255 area 0


hostname A1!interface ATM1/0/0description Connection to R1

!interface ATM1/0/1 description Connection to A2atm pvp 2 interface ATM1/0/0 2!


hostname A2!interface ATM1/0/0 description connection to R2!interface ATM1/0/1 description connection to A1 atm pvp 2 interface ATM1/0/0 2!


hostname R2!ip cef!interface Loopback0 ip address 10.10.10.104 255.255.255.255!interface Ethernet0 ip address 10.10.20.129 255.255.255.252!interface ATM2/0!interface ATM2/0.1 mpls description connection to A2 ip address 10.10.20.10 255.255.255.252 mpls ip mpls atm vp-tunnel 2 vci-range 33-65535!





router ospf 100network 10.10.0.0 0.0.255.255 area 0

Implementing Cell-Mode MPLS with BPX8600 and 7200 as Label Switch ControllerCell-mode MPLS can also be implemented by separating the control and data planefunctions of an ATM LSR. The control plane function is performed by a device called theLSC or label switch controller, and the data plane function can be performed by an ATMswitch such as the BPX8600 Series ATM switches. In the BPX with LSC design, the LSCis connected to the BPX ATM switch by trunks that can carry PVCs, SVCs, or MPLS LabelVCs (LVCs). The control software is physically located in the LSC that is connected to theATM switch by a physical connection also called the virtual switch interface (VSI) controllink. The VSI control link could be an STM-1 link connected to a single port of a broadbandswitching module (BXM) linecard on the BPX8600. This is shown in Figure 2-14.

Figure 2-14. BPX with LSC as LSR

In Figure 2-14, the functions control plane is implemented using a BPX+LSC. The figureoutlines a connection from each of the Edge ATM LSRs to the LSC connected to the BPXswitch using LVCs. These signaling LVCs are maintained per LSR that the BPX+LSC isconnected to. In addition, VSI control links are maintained per card on the BPX.





From a data plane perspective, data label VCs bypass the LSC and are switched using theBPX ports. Therefore, in the data plane, the traffic via the ATM label switch router traversesonly the BPX ATM switch and not the LSC.The signaling label VCs are on VPI/VCI values of 0/32 by default and will be cross-connected to a different VCI on the switch control link between the BPX and LSC. One keything to note is that the LSC functions as the VSI master and the BPX functions as the VSIslave.Configuring BPX+LSC as ATM LSRThis section deals with the configuration of a BPX+LSC as an ATM LSR to implement cell-mode MPLS. The topology used to implement this configuration is shown in Figure 2-15.

Figure 2-15. BPX and LSC as ATM LSR: Topology

Figure 2-15 shows the physical connections for this section in which two Edge ATM LSRsare connected to a BPX 8600 switch. The LSC (7200 router) is also connected on the sameswitch. The numbers 2.1, 2.2, and 2.3 in Figure 2-15 pertain to slot.port on the BPX 8600switch. The only IP addresses shown in this figure are those of the loopbacks on the LSRand ELSRs. Figure 2-16 shows the Edge ATM LSRs connected to the LSC in the controlplane using the VSI control VCs as well as the signaling LVCs that originate from anmpls subinterface on the Edge ATM LSR and terminate on an XtagATM interface on theLSC. The XtagATM interface controls the trunks on the BPX that are connected to otherLSRs.





Figure 2-16. BPX and LSC as ATM LSR: Control Plane

Configuring the BPXThe steps to configure the BPX are as follows:

Step 1. Verify the cards on the BPX by issuing dspcds command. As shown in Example2-60, the BXM-155 card connects and configures the trunks on the BPX as well asthe appropriate resources on the ports.Example 2-60. Viewing Cards on BPX

bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:18 MST

FrontCard BackCard FrontCard BackCard Type Rev Type Rev Status Type Rev Type Rev Status1 BME-622 KMB SM-2 BD Standby 9 Empty2 BXM-155 FJL MM-8 BB Active 10 Empty3 BXM-T3 FJL TE3-12BA Active 11 Empty4 BXM-622 FML SM-2 BD Standby 12 Empty5 BXM-155 FAL SM-4 BB Standby 13 Empty6 BXM-622 FPH SM-2 BE Standby 14 Empty7 BCC-4 HDM LM-2 AC Active 15 ASM ACC LMASM AC Active8 Empty reserved for Card

Last Command: dspcdsNext Command:

Step 2. Enable the trunks on the ports 2.1, 2.2, and 2.3. This is as shown in Example2-60. Example 2-61 shows only the command to be used in the "next command"section to enable the three trunks connecting to the two Edge ATM LSRs as well asthe LSC.





Example 2-61. Configuring Trunks on the BPX (Commands)

Next Command: uptrk 2.1Next Command: uptrk 2.2Next Command: uptrk 2.3

When the trunks are configured, view the trunk configuration using the dsptrkscommand, as shown in Example 2-62.Example 2-62. Viewing Trunk Configuration


TRK Type Current Line Alarm Status Other End 2.1 OC3 Clear - OK - 2.2 OC3 Clear - OK - 2.3 OC3 Clear - OK -

Last Command: dsptrksNext Command:

Step 3. Configuration of resources applied to the trunks already configured is performedusing the cnfrsrc command on the BPX, as shown in Example 2-63.Example 2-63. Configuring Resources

bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:29 MSTPort/Trunk : 2.1Maximum PVC LCNS: 256 Maximum PVC Bandwidth:247207 (Statistical Reserve: 1000)Partition 1Partition State : EnabledMinimum VSI LCNS: 600Maximum VSI LCNS: 1500Start VSI VPI: 240End VSI VPI : 255Minimum VSI Bandwidth : 105000 Maximum VSI Bandwidth : 105000VSI ILMI Config : 0VSI Topo Dsc : 0 VSI Ses Ctrlr Id : 255

Last Command: cnfrsrc 2.1 256 247207 y 1 e 600 1500 240 255 105000 105000

The command in Example 2-63 can be explained as "configure resources for trunk2.1 where the maximum PVC LCNs are 256, the maximum PVC bandwidth is247207; editing of VSI information is enabled, Partition ID is 1 and is enabled; themaximum VSI LCNs are 600 and the maximum VSI LCNs are 1500; the VSI VPI-range is configured to be between 240255 and the minimum and maximum VSIbandwidths is 105000."





Repeat this command to configure resources for trunks 2.2 and 2.3. However, alltrunks need to be part of the same partition (1). When completed, a dsprsrc issuedfor the appropriate trunk and partition IDs, as shown in Example 2-64, shows theresources allocated to the trunk.Example 2-64. Display Configured Resources

bpxa TRM cisco:1 BPX 8620 9.2.30 Oct. 8 2004 15:37 MSTPort/Trunk : 2.2Maximum PVC LCNS: 256 Maximum PVC Bandwidth:247207 (Statistical Reserve: 1000)Partition 1Partition State : EnabledMinimum VSI LCNS: 512Maximum VSI LCNS: 1500Start VSI VPI: 240End VSI VPI : 255Minimum VSI Bandwidth : 105000 Maximum VSI Bandwidth : 105000VSI ILMI Config : 0VSI Topo Dsc : 0 VSI Ses Ctrlr Id : 255

Last Command: dsprsrc 2.2 1

Step 4. MPLS labeled packets use the queues 1014 on each port (one queue per class). Toenable MPLS packet forwarding, configure the queues using the cnfqbincommand. Example 2-65 shows the command to configure the qbin 10 on BPXtrunk 2.2 as well as the output of the configuration.Example 2-65. Configuring Qbin's on BPX Ports for MPLS


Qbin Database 2.2 on BXM qbin 10 (Configured by User) (EPD Enabled on this qbin)

Qbin State: EnabledDiscard Threshold: 65536 cellsEPD Threshold: 95%High CLP Threshold: 100%EFCI Threshold: 40%Last Command: cnfqbin 2.2 10 e n 65536 95 100 40

Step 5. Finally, add an LSC shelf as a VSI master using the addshelf command. InExample 2-66, the first "1" after "VSI" is the VSI controller ID, which must be setthe same on both the BPX 8650 and the LSC. The default controller ID on the LSCis "1." The second "1" after "VSI" is the partition ID that indicates thi

basic mpls configuration

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