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Frame-Mode MPLS Implementation on Cisco IOS Platforms

Frame-Mode MPLS Implementation on Cisco IOS Platforms. Configuring Frame-Mode MPLS on Cisco IOS Platforms. 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

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Frame-Mode MPLS Implementation on Cisco IOS Platforms

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  1. Frame-Mode MPLS Implementation on Cisco IOS Platforms Configuring Frame-Mode MPLS on Cisco IOS Platforms

  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

  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

  4. Configuring the MPLS ID on a Router Router(config)# mpls ldp router-id interface [force] • 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-idcommand to force the use of the named interface as the LDP router ID

  5. Configuring MPLS on a Frame-Mode Interface Router(config-if)# mpls ip • Enables label switching on a frame-mode interface • Starts LDP on the interface Router(config-if)# mpls label protocol [tdp | ldp | both] • Starts selected label distribution protocol on the specified interface

  6. Configuring MPLS on a Frame-Mode Interface: Example 1

  7. Configuring MPLS on a Frame-Mode Interface: Example 2

  8. VerifyingMPLS on a Frame-Mode Interface: Example PE51(config)# int ser 0/0.111PE51(config-if)# mpls ipPE51(config-if)# mpls label protocol ldpPE51(config-if)#^Z PE51#show running-config int ser 0/0.111Building configuration...Current configuration : 165 bytes!interface Serial0/0.111 point-to-point ip address 192.168.5.49 255.255.255.240 mpls label protocol ldp tag-switching ip frame-relay interface-dlci 111endPE51#

  9. Configuring a Label-Switching MTU Router(config-if)# mpls mtu bytes • Label switching increases the maximum MTU requirements on an interface because ofthe 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.

  10. Configuring Label-Switching MTU: Example

  11. Configuring IP TTL Propagation Router(config)# no mpls ip propagate-ttl • 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.

  12. Configuring IP TTL Propagation:Example

  13. Configuring IP TTL Propagation:Disabling IP TTL Propagation Example

  14. Configuring IP TTL Propagation:Extended Options Router(config)# no mpls ip propagate-ttl [forwarded | local] 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.)

  15. Configuring IP TTL Propagation:Disabling IP TTL Propagation Example

  16. Conditional Label Distribution Configuration Router(config)# mpls ldp advertise-labels[for prefix-access-list[to peer-access-list]] • By default, labels for all destinations are announcedto 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 thedestinations for which the labels will be generated • topeer-access-list—The IP access list that selects the MPLS neighbors that will receive the labels

  17. Conditional Label Distribution Configuration: Example • The customer is already running IP infrastructure. • MPLS is needed only to support MPLSVPN services: • Labels should be generated only for loopback interfaces (BGP next hops) of all routers. • All loopback interfaces are in one contiguous address block (192.168.254.0/24).

  18. Step 1: Enable CEF and label switching. Conditional Label Distribution ConfigurationSteps ip cef ! interface serial 0/0 mpls ip! interface serial 0/1 mpls ip ! interface ethernet 1/0 mpls ip ip cef mpls ip mpls ip mpls ip

  19. Step 2: Enable conditional label advertisement. Conditional Label Distribution ConfigurationSteps (Cont.) ! ! 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 192.168.254.0 0.0.0.255 access-list 91 permit ip any no mpls ldp advertise-labels mpls ldp advertise-labels for 90 to 91 ! access-list 90 permit 192.168.254.0 0.0.0.255 access-list 91 permit any

  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.

  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

  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.)

  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

  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.

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