350-501 · Question #238
What is a constraint of Cisco MPLS TE tunnel configurations?
The correct answer is C. Tunnels cannot be configured over IP unnumbered links. Cisco MPLS Traffic Engineering (TE) tunnels have a fundamental constraint where they cannot be configured to traverse IP unnumbered links due to their reliance on specific IP addresses for path computation and label distribution.
Question
What is a constraint of Cisco MPLS TE tunnel configurations?
Options
- ATunnels cannot span multiple OSPF areas.
- BWith ISIS as an IGP. only older-style metrics are used.
- CTunnels cannot be configured over IP unnumbered links.
- DQoS-aware tunneling is not supported.
How the community answered
(34 responses)- A3% (1)
- C94% (32)
- D3% (1)
Why each option
Cisco MPLS Traffic Engineering (TE) tunnels have a fundamental constraint where they cannot be configured to traverse IP unnumbered links due to their reliance on specific IP addresses for path computation and label distribution.
MPLS TE tunnels can span multiple OSPF areas because TE operates over the IGP's topology database, which can include inter-area information, allowing for multi-area path computation.
IS-IS as an IGP supports both standard and TE-specific metrics (e.g., TE metric) for MPLS TE path computation, not just older-style metrics.
MPLS TE requires IP addressing on interfaces to establish and maintain tunnels, making IP unnumbered links incompatible with its operation for path calculation and label distribution, as the head-end router needs known next-hop IP addresses.
QoS-aware tunneling is a core feature of MPLS TE, enabling tunnels to reserve bandwidth and ensure specific quality of service requirements for traffic.
Concept tested: MPLS TE constraints with IP unnumbered links
Source: https://www.cisco.com/c/en/us/td/docs/ios/mpls/configuration/guide/mp_te_tunnl_psg_cg.html
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