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350-501 · Question #561

What is the feature of the Unified MPLS architecture?

The correct answer is C. It exchanges label information using BGP. A key feature of the Unified MPLS architecture is its use of BGP to exchange MPLS label information, enabling scalable and hierarchical MPLS deployments.

Architecture

Question

What is the feature of the Unified MPLS architecture?

Options

  • AIt uses a flat Level 2 or backbone area network throughout the entire IGP domain
  • BABR routers are part of the iBGP mesh design and participate in exchange of all VPN prefixes
  • CIt exchanges label information using BGP
  • DThe MPLS label stack reqquires 8bytes of overhead between the ingress and egress PEs

How the community answered

(37 responses)
  • A
    5% (2)
  • B
    3% (1)
  • C
    89% (33)
  • D
    3% (1)

Why each option

A key feature of the Unified MPLS architecture is its use of BGP to exchange MPLS label information, enabling scalable and hierarchical MPLS deployments.

AIt uses a flat Level 2 or backbone area network throughout the entire IGP domain

Unified MPLS aims to avoid a flat network, instead using a hierarchical design, often with multiple IGP levels to improve scalability and reduce IGP database size.

BABR routers are part of the iBGP mesh design and participate in exchange of all VPN prefixes

While ABRs are crucial, Unified MPLS's scalability with BGP means not all routers need to be part of a full iBGP mesh exchanging all VPN prefixes; route reflectors are typically used.

CIt exchanges label information using BGPCorrect

Unified MPLS is a hierarchical MPLS architecture that leverages BGP to exchange label information, particularly for distributing labels for VPN prefixes or other services across different IGP domains or levels. This BGP-based label distribution (BGP Labeled Unicast - BGP-LU) allows for a scalable and segmented MPLS network design.

DThe MPLS label stack reqquires 8bytes of overhead between the ingress and egress PEs

A single MPLS label is 4 bytes, so a label stack requires 4 bytes per label; 8 bytes implies two labels, which is common but not a defining or unique feature of Unified MPLS itself.

Concept tested: Unified MPLS architecture features, BGP label distribution

Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-3s/asr1000/irg-xe-3s-asr1k-book/irg-unified-mpls.html

Topics

#Unified MPLS#BGP Labeled Unicast#Label Distribution#MPLS Architecture

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