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When a service provider does not support multicast over their Layer 3 VPN, the enterprise can useGRE tunnels between Customer Edge (CE) devicesto transport multicast traffic. This method allows the customer to encapsulate multicast packets in unicast GRE packets, which are routable through the provider’s non-multicast core.

In this scenario, the most scalable and immediate solution is to establish a GRE tunnel betweenC2 (in the head office CE router path)andC4 (at the branch office). This setup ensures that multicast traffic originating at the head office is tunneled directly to the multicast receivers, bypassing the service provider’s non-multicast-aware core.

This strategy is directly aligned with CCDE v3.1 principles, which emphasize:

Minimizing service provider dependency

Providing a scalable, customer-controlled overlay solution

Ensuring protocol compatibility across domains

Why other options are incorrect:

A: Tunnel between CE1 and CE2 is less optimal, as it may not originate or terminate at the exact multicast endpoints.

C: Tunnel between C1 and C4 is less aligned with CE-to-CE design expectations and may bypass required edge security/policy controls.

D: 2547oDMVPN is more complex and intended for full-scale VPN overlays, not quick multicast solutions.

E: Draft Rosen requires service provider support, which is currently unavailable, hence not a valid short-term option.

This solution ensures operational simplicity and future scalability with minimal provider dependency, which are core principles outlined in the CCDE v3.1 design methodology.

The IS-IS Overload Bit allows a router to signal to its peers that it should be temporarily excluded from SPF calculations for transit traffic:

A: The Overload Bit can be automatically set at startup (known as "startup overload") to allow the router sufficient time to converge IGP, BGP, and stabilize protocols before accepting transit traffic.

D: The bit can remain set until all dependent protocols have converged and the router is fully operational.

Why other options are incorrect:

B: The router’s directly connected prefixes remain reachable; only transit path calculations exclude the overloaded node.

C: MPLS-TE does not automatically reoptimize tunnels based on the Overload Bit.

E: There is no specific restriction preventing Overload Bit usage on Route Reflectors.

The two most common challenges for organizations adopting container technologies are:

B (Security): Containers introduce unique security challenges, such as shared kernels, namespace isolation, image vulnerabilities, and orchestration exposure.

E (Skilled staff): Containerization requires specialized skills in orchestration (e.g., Kubernetes), CI/CD, and microservices design, which may not be readily available in many IT teams.

Other options explained:

A: Performance is generally good for containers; overhead is minimal.

C: Cost savings are often a driver for containerization.

D: Deployment is streamlined via orchestration platforms.

F: Compliance is important but less frequently cited as the initial adoption barrier.

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Let’s calculate total 1-year cost for each option using the provided table:

DWDM over dark fiber:

CAPEX = $250,000

OPEX (1 year) = $100,000

Installation fee = $30,000

Total = $250,000 + $100,000 + $30,000 = $380,000

CWDM over dark fiber:

CAPEX = $150,000

OPEX (1 year) = $100,000

Installation fee = $25,000

Total = $150,000 + $100,000 + $25,000 = $275,000

MPLS wires only:

CAPEX = $50,000

OPEX (1 year) = $80,000

Installation fee = $5,000

Total = $50,000 + $80,000 + $5,000 = $135,000

BUT: MPLS does not allow customer-controlled QoS policies as stated in the requirement (cannot run its own varying QoS profiles without SP interaction). Therefore disqualified.

Metro Ethernet:

CAPEX = $45,000

OPEX (1 year) = $100,000

Installation fee = $5,000

Total = $45,000 + $100,000 + $5,000 = $150,000

BUT: Metro Ethernet is also typically a service provider-managed solution where customer-controlled QoS is usually limited depending on SP capabilities. May not fully meet the requirement.

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The key technical requirement:

“Be able to run its own varying QoS profiles without service provider interaction.”

This clearly favors dark fiber solutions (CWDM and DWDM), as these give full Layer 1 control to the customer, allowing complete freedom in managing QoS, traffic engineering, and prioritization internally.

Among the two dark fiber options, CWDM over dark fiber is the most cost-effective choice for one year at $275,000.

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Therefore, final correct answer: