© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-1 Frame-Mode MPLS Implementation on Cisco IOS Platforms Configuring Frame-Mode MPLS on Cisco IOS Platforms

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-2 Outline Overview What Are MPLS Configuration Tasks? Configuring the MPLS ID on a Router Configuring MPLS on a Frame-Mode Interface Configuring a Label-Switching MTU Configuring IP TTL Propagation Configuring Conditional Label Distribution Configuring Frame-Mode MPLS on Switched WAN Media Summary

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-3 MPLS Configuration Tasks Mandatory: Enable CEF switching Configure LDP on every label-enabled interface Optional: Configure the MPLS ID Configure MTU size for labeled packets Configure IP TTL propagation Configure conditional label advertising

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-4 mpls ldp router-id interface [force] Router(config)# Specifies a preferred interface for determining the LDP router ID: Parameters –interface: Causes the IP address of the specified interface to be used as the LDP router ID, provided that the interface is operational –force: Alters the behavior of the mpls ldp router-id command to force the use of the named interface as the LDP router ID Configuring the MPLS ID on a Router

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-5 Configuring MPLS on a Frame-Mode Interface mpls ip Router(config-if)# Enables label switching on a frame-mode interface Starts LDP on the interface mpls label protocol [tdp | ldp | both] Router(config-if)# Starts selected label distribution protocol on the specified interface

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-6 Configuring MPLS on a Frame-Mode Interface: Example 1

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-7 Configuring MPLS on a Frame-Mode Interface: Example 2

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-8 PE51(config)# int ser 0/0.111 PE51(config-if)# mpls ip PE51(config-if)# mpls label protocol ldp PE51(config-if)#^Z PE51#show running-config int ser 0/0.111 Building configuration... Current configuration : 165 bytes ! interface Serial0/0.111 point-to-point ip address mpls label protocol ldp tag-switching ip frame-relay interface-dlci 111 end PE51# Verifying MPLS on a Frame-Mode Interface: Example

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-9 Configuring a Label-Switching MTU mpls mtu bytes Router(config-if)# Label switching increases the maximum MTU requirements on an interface because of the additional label header. Interface MTU is automatically increased on WAN interfaces; IP MTU is automatically decreased on LAN interfaces. Label-switching MTU can be increased on LAN interfaces (resulting in jumbo frames) to prevent IP fragmentation. The jumbo frames are not supported by all LAN switches.

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-10 Configuring Label-Switching MTU: Example

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-11 Configuring IP TTL Propagation no mpls ip propagate-ttl Router(config)# By default, IP TTL is copied into the MPLS label at label imposition, and the MPLS label TTL is copied (back) into the IP TTL at label removal. This command disables IP TTL and label TTL propagation. –TTL value of 255 is inserted in the label header. The TTL propagation has to be disabled on ingress and egress edge LSRs.

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-12 Configuring IP TTL Propagation: Example

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-13 Configuring IP TTL Propagation: Disabling IP TTL Propagation Example

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-14 no mpls ip propagate-ttl [forwarded | local] Router(config )# Selectively disables IP TTL propagation for: Forwarded traffic (Traceroute does not work for transit traffic labeled by this router.) Local traffic (Traceroute does not work from the router but works for transit traffic labeled by this router.) Configuring IP TTL Propagation: Extended Options

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-15 Configuring IP TTL Propagation: Disabling IP TTL Propagation Example

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-16 mpls ldp advertise-labels [for prefix-access-list [to peer- access-list]] Router(config)# By default, labels for all destinations are announced to all LDP or TDP neighbors. This command enables you to selectively advertise some labels to some LDP or TDP neighbors. Conditional label advertisement works only over frame-mode interfaces. Parameters: –for prefix-access-list —The IP access list that selects the destinations for which the labels will be generated –to peer-access-list —The IP access list that selects the MPLS neighbors that will receive the labels Conditional Label Distribution Configuration

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-17 The customer is already running IP infrastructure. MPLS is needed only to support MPLS VPN services: –Labels should be generated only for loopback interfaces (BGP next hops) of all routers. –All loopback interfaces are in one contiguous address block ( /24). Conditional Label Distribution Configuration: Example

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-18 ip cef ! interface serial 0/0 mpls ip ! interface serial 0/1 mpls ip ! interface ethernet 1/0 mpls ip Conditional Label Distribution Configuration Steps Step 1: Enable CEF and label switching. ip cef mpls ip

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-19 Conditional Label Distribution Configuration Steps (Cont.) Step 2: Enable conditional label advertisement. ! ! Disable default advertisment mechanism ! no mpls ldp advertise-labels ! ! Configure conditional advertisments ! mpls ldp advertise-labels for 90 to 91 ! access-list 90 permit ip access-list 91 permit ip any no mpls ldp advertise-labels mpls ldp advertise-labels for 90 to 91 ! access-list 90 permit access-list 91 permit any

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-20 Configuring Frame-Mode MPLS on Switched WAN Media Why: Run MPLS over ATM networks that do not support MPLS. This could be the potential first phase in ATM network migration. How: Configure MPLS over ATM point-to-point subinterfaces on the routers.

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-21 Routers view the ATM PVC as a frame-mode MPLS interface. TDP or LDP is run between the adjacent routers. Many LSPs can be established over one ATM PVC. The ATM network is not aware of MPLS between the routers. Configuring Frame-Mode MPLS on Switched WAN Media: MPLS over ATM Forum PVCs

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-22 Create a point-to-point ATM subinterface. Configure ATM PVC on the subinterface. Start label switching and LDP or TDP on the interface. Configuring Frame-Mode MPLS on Switched WAN Media: MPLS over ATM Forum PVCs (Cont.)

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-23 Create a point-to-point or multipoint Frame Relay subinterface. Configure Frame Relay DLCI on the subinterface. Start label switching and LDP or TDP on the interface. Configuring Frame-Mode MPLS on Switched WAN Media: MPLS over Frame Relay Networks

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-24 Summary Some of the MPLS configuration tasks are mandatory and some are optional. The command mpls ldp router-id interface [force] specifies a preferred interface for determining the LDP router ID. Use the mpls ip or tag-switching ip commands to enable MPLS (interface level). Label switching increases maximum MTU size on an interface. TTL propagation must be disabled on ingress and egress edge LSRs. Conditional label advertisement works only on frame-mode interfaces. When frame-mode MPLS on an ATM interface is enabled, LDP relationships are established between the PVC endpoints and not with the attached ATM switch.

© 2006 Cisco Systems, Inc. All rights reserved. MPLS v2.2—3-25