MPLS Traffic Engineering (TE) OSPF Configuration

This topic is to discuss the following lesson:

Dear, i got this while following your tutorial

PE1(config)#mpls traffic-eng area 0
^(arrow symbol under area)
% Invalid input detected at ‘^’ marker.

PE1(config)#mpls traffic-eng ?
atm Preformatted text Traffic Engineering ATM parameters
uto-bw auto-bw parameters
link-management Link Management configuration
logging Trap logging configuration
path-selection Path Selection Configuration
reoptimize Reoptimization parameters
signalling Traffic Engineering Signalling Parameters
topology Topology Database Configuration
tunnels Traffic Engineering tunnels

Should i do instead this ?

configure terminal
mpls traffic-eng tunnels
router ospf 1
mpls traffic-eng router-id loopback0
mpls traffic-eng area 0

Hello Mehdi

You attempted to issue the following command:

PE1(config)#mpls traffic-eng area 0

However, you are in global configuration mode. This command is only available under OSPF configuration mode. So the correct method, as shown in the lesson is to do this:

PE1(config)#router ospf 1
PE1(config-router)#mpls traffic-eng area 0

The above command is issued under the OSPF configuration mode which is entered using the router ospf 1 command. So yes, you should issue the commands you suggested instead.

I hope this has been helpful!


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For the MPLS-TE OSPF configuration, why we are using both LDP and RSVP, when the RSVP alone can also generate the labels.

On each contributing interface, we have both
- mpls ip
- ip rsvp bandwidth

Hello Zaygham

You are correct that RSVP can indeed generate labels. However, in an MPLS-TE configuration using OSPF, both LDP and RSVP can be used, but when they’re used together, they serve different purposes. Here’s a detailed explanation of why both are often used together:

Here are some reasons to use both Both LDP and RSVP together:

  1. Dual Use Cases:

    • LDP for Standard Traffic: LDP can be used for general-purpose traffic where strict path requirements and resource reservations are not needed. This ensures that basic MPLS forwarding is always available, leveraging the simplicity of LDP.
    • RSVP for TE Traffic: RSVP is used for specific traffic engineering needs, where traffic demands explicit paths, bandwidth reservations, or other constraints. This allows for better control and optimization of network resources for critical traffic flows.
  2. Separation of Concerns:

    • Using both protocols allows for a clear separation between standard MPLS forwarding (handled by LDP) and traffic-engineered paths (handled by RSVP). This separation simplifies network management and ensures that each protocol is used for its intended purpose.
  3. Compatibility and Redundancy:

    • Having both LDP and RSVP configured provides a fallback mechanism. If RSVP fails to establish a TE tunnel, the traffic can still fall back to an LDP-signaled LSP, ensuring continuity of service.
  4. Granular Control:

    • By configuring both, network operators can have granular control over which traffic should use traffic-engineered paths and which should use default LDP paths. This is particularly useful in complex networks where different traffic types have different service requirements.

Using both LDP and RSVP in MPLS-TE configurations provides flexibility, redundancy, and optimized use of network resources. LDP handles standard label distribution for best-effort traffic, while RSVP handles the more complex requirements of traffic-engineered paths. This dual approach ensures that the network can support a wide range of service requirements and maintain high performance and reliability.

I hope this has been helpful!