This chapter discussed advanced MPLS topics that are not necessarily needed to successfully deploy an MPLS backbone, but could become very useful during advanced network design or troubleshooting.

You can control several advanced mechanisms in Cisco IOS:

  • Controlled label distribution, where you can fine-une which packets are label-switched and which packets are IP-routed by controlling which labels an LSR announces to its upstream neighbors

  • MPLS MTU on a LAN segment in combination with increased physical MTU on the same segment, which allows maximum-sized IP packets to be propagated across Ethernet-type media as giant frames without being fragmented

  • IP TTL propagation, with which you can control whether an end-host connected to an MPLS network can perform a traceroute across that network

  • atm maxhops parameter, which allows you to fine-tune loop prevention in ATM environments

    Part 2: MPLS-based Virtual Private Networks