Discuss Cisco 350-501 Exam Topic 4 Question 120

What is a constraint of Cisco MPLS TE tunnel configurations?

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.

Suggested Answer: D

Cisco MPLS TE (Traffic Engineering) tunnels provide a way to optimize traffic routing within an MPLS network. However, there are certain constraints to be aware of:

QoS-aware tunneling: Unfortunately, Cisco MPLS TE tunnels do not inherently support Quality of Service (QoS) awareness. This means that the tunnels themselves do not directly consider QoS parameters when making routing decisions. QoS policies must be applied separately at the network level, and the TE tunnels do not inherently take QoS into account during path selection.

Tunnels spanning multiple OSPF areas: Contrary to option A, Cisco MPLS TE tunnels can indeed span multiple OSPF areas. The use of OSPF areas does not inherently restrict the creation of MPLS TE tunnels across area boundaries.

ISIS metrics: Option B is incorrect. When using ISIS (Intermediate System to Intermediate System) as the Interior Gateway Protocol (IGP), newer-style metrics (such as wide metrics) are supported. Older-style metrics are not the only option.

Tunnels over IP unnumbered links: Option C is also incorrect. Cisco MPLS TE tunnels can be configured over IP unnumbered links, allowing efficient use of IP addresses.

In summary, the primary constraint is the lack of built-in QoS awareness within MPLS TE tunnels.

Implementing an MPLS VPN over TE Tunnels - Cisco Support

Configuring Basic MPLS TE - Cisco NX-OS

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30 comments · newest first

Arletta 6 months ago

I lean towards A. It’s a common issue in setups.

Antonio 7 months ago

D is a concern. QoS is crucial for performance.

Janey 7 months ago

C is tricky. Unnumbered links can be useful sometimes.

Tawna 7 months ago

B seems plausible too. Older metrics can be a hassle.

Elden 7 months ago

I agree with A. It limits our design options.

Denna 7 months ago

C) is a bummer, unnumbered links are common!

Brandee 8 months ago

B) is true, older metrics only with ISIS.

Reena 8 months ago

Wait, are you serious? I thought they could!

Jina 8 months ago

Totally agree, that can complicate things a lot!

Brice 8 months ago

Haha, who even uses ISIS these days? Cisco should just focus on OSPF.

Aleshia 9 months ago

B? Really? Using older-style metrics with ISIS? That's just weird.

Franklyn 9 months ago

C is the correct answer. Tunnels can't be configured over IP unnumbered links, that's a key limitation.

Lai 9 months ago

I think the answer is A. Tunnels can't span multiple OSPF areas, that's a well-known constraint.

Tegan 9 months ago

I’m pretty sure tunnels can’t be configured over IP unnumbered links, but I need to double-check that against my notes.

Edna 9 months ago

I feel like I've seen a question about QoS and MPLS before, but I can't recall if QoS-aware tunneling is actually supported or not.

Izetta 9 months ago

Hmm, this is a tricky one. I'm not as familiar with the MPLS TE specifics as I'd like to be. I'll have to eliminate the options I'm less sure about and make an educated guess on this one.

Dolores 10 months ago

I'm pretty confident the answer is C. I remember the instructor specifically mentioning that MPLS TE tunnels can't traverse unnumbered links. Gotta watch out for those tricky configuration details!

Martin 10 months ago

Okay, let me think this through. I know MPLS TE is used for traffic engineering, so the constraints are probably related to that. I'm leaning towards A or C, but I'll have to double-check my notes to be sure.

Glory 10 months ago

A) Tunnels cannot span multiple OSPF areas is a big limitation.

Rasheeda 10 months ago

I think A is correct. Tunnels and OSPF areas don’t mix well.

Tammy 10 months ago

I think I remember something about OSPF areas and tunnels not being able to span them, but I'm not entirely sure if that's the right answer.

Gail 11 months ago

I’m leaning towards option A, but I also remember something about ISIS metrics being a potential issue. It’s a bit confusing!

Merissa 11 months ago

D is the right answer. QoS-aware tunneling is not supported in Cisco MPLS TE.

Shanice 11 months ago

I'm not too sure about this one. I know MPLS TE has some limitations, but I can't recall the specifics off the top of my head. Guess I'll have to think it through carefully.

Valentin 11 months ago

Hmm, I think the answer is C. I remember from the lectures that MPLS TE tunnels can't be configured over unnumbered interfaces.

Ivan 6 months ago

↳ replying to Valentin

True, C is definitely a constraint in MPLS TE.

Dorothy 6 months ago

↳ replying to Valentin

A is also a valid point, but C is more specific.

Elbert 6 months ago

↳ replying to Valentin

But what about A? Tunnels spanning OSPF areas?

Brittani 6 months ago

↳ replying to Valentin

Yeah, I remember that too. It’s a limitation.

Gilma 6 months ago

↳ replying to Valentin

I agree, C seems correct. Unnumbered links are tricky.

Cisco 350-501 Exam - Topic 4 Question 120 Discussion