MPLS Traffic Engineering

MPLS TE allows the MPLS-enabled network to replicate and expand upon the TE capabilities of Layer 2 ATM and Frame Relay networks. MPLS uses the reachability information provided by Layer 3 routing protocols and operates like a Layer 2 ATM network. With MPLS, TE capabilities are integrated into Layer 3, which can be implemented for efficient bandwidth utilization between routers in the SP network.


MPLS traffic engineering automatically establishes and maintains the tunnel across the backbone, using RSVP. The path used by a given tunnel at any point in time is determined based on the tunnel resource requirements and network resources, such as bandwidth.

Available resources are flooded via extensions to a link-state based Interior Gateway Protocol  (IGP).

MPLS traffic engineering is built on the following IOS mechanisms:

  • Label-switched path (LSP) tunnels, which are signalled through RSVP, with traffic engineering extensions. LSP tunnels are represented as IOS tunnel interfaces, have a configured destination, and are unidirectional.
  • A link-state IGP (such as IS-IS) with extensions for the global flooding of resource information, and extensions for the automatic routing of traffic onto LSP tunnels as appropriate.
  • An MPLS traffic engineering path calculation module that determines paths to use for LSP tunnels.
  • An MPLS traffic engineering link management module that does link admission and bookkeeping of the resource information to be flooded.
  • Label switching forwarding, which provides routers with a Layer 2-like ability to direct traffic across multiple hops as directed by the resource-based routing algorithm.


All routers need to have the following configuration


OSPF must be configured to flood opaque LSA´s.   Like any other LSA, the Opaque LSA uses the link-state database distribution mechanism for flooding this information throughout the topology. so thought all devices we configured:


the Opaque LSA has a flooding scope associated with it so that the scope of flooding may be link-local (type 9), area-local (type 10) or the entire OSPF routing domain (type 11).  If you look at the ospf database on either of these routers now, you will see and entry for the new LSA types.


Each router creates a new Link ID for each link that traffic-eng is configured.


here we can see that the Maximum Bandwidth is 193000 bytes, but only 75% is available for bandwidth reservation.

now lets configure a tunnel


here, we can confirm that the tunnel is operational and that it’s a dynamic tunnel


The tunnel runs over the directly connected interfaces between R1 and R5 because that’s the shortest path to the tunnel destination.


Now let see an explicit path configuration



A Networker Blog

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