Free Practice Questions for Cisco 400-007 Exam

To conserve IPv4 addresses and achieve fast convergence:

B: Using /31 subnets for point-to-point (P2P) links enables each link to consume only two IP addresses. This is widely supported and conserves address space.

C: A hub-and-spoke design with P2P links minimizes the number of neighbor relationships and simplifies routing convergence.

Other options:

A: Multipoint Metro-E introduces neighbor adjacency complexity and DR/BDR elections, which delay convergence.

D: Aggregation is more applicable to prefix summarization, not address conservation per link.

E: DR/BDR roles apply only in broadcast/multicast environments, not P2P links.

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C (Class-Based Weighted Fair Queuing - CBWFQ): CBWFQ allows assigning bandwidth limits (in this case, 2 Mbps) to specific traffic classes, effectively controlling scavenger traffic without dropping excess packets unnecessarily.

Other options explained:

A: Policing drops excess traffic immediately rather than queuing.

B: LLQ is for delay-sensitive traffic, not scavenger control.

D: Shaping is useful but typically applied at interface level, not specific traffic classes.

In a DMVPN (Dynamic Multipoint VPN) design:

One site (here, Chicago) functions as the Next Hop Server (NHS), which facilitates dynamic spoke-to-spoke tunnel establishment.

DMVPN is based on multipoint GRE tunnels combined with NHRP (Next Hop Resolution Protocol).

The ability to detect remote tunnel endpoint failures is essential for reliable routing convergence and tunnel restoration.

While GRE (Option C) is the encapsulation mechanism used in DMVPN, it does not inherently provide failure detection. Likewise, VPLS and L2TPv3 are Layer 2 VPN technologies and not applicable in DMVPN design.

To meet the requirement of peer failure detection, the correct mechanism is:

B. IP SLA (Service-Level Agreement): This is a feature that actively monitors the health and reachability of tunnel endpoints through periodic probes (e.g., ICMP echo). When the peer becomes unreachable, routing protocol adjacencies can be withdrawn, and alternate paths selected.

Using IP SLA in a DMVPN design helps detect endpoint failure scenarios such as:

A spoke going down unexpectedly

Loss of return traffic

Partial link failures

This design pattern is aligned with CCDE v3.1 "Protocol Design Implications", emphasizing resiliency, fault detection, and efficient routing convergence in overlay VPN designs like DMVPN.

C (Both modes use control packets):Regardless of whether echo packets are used, BFD asynchronous mode always relies on periodic transmission of control packets to verify session liveliness.

E (Echo mode uses separate packets):When echo is enabled, the echo packets are transmitted in addition to control packets, providing even faster failure detection by relying on data plane processing.

Other options explained:

A: Control and echo packets are never combined into a single packet.

B: Both modes always use control packets; echo packets are optional.

D: BFD echo packets are locally looped, not reflected back from the remote device.

Inbound traffic engineering is best controlled by manipulating how external ASes view your routes.

AS path prepending on the 91.7.0.0/16 prefix towards AS 200 makes AS 500 prefer the less-prepended path through AS 100.

This allows granular inbound control for that specific prefix while leaving the rest of the traffic unchanged.

Why other options are incorrect:

B: Extended community is not used for direct inbound path manipulation.

C: Local preference affects outbound traffic, not inbound path selection by remote ASes.

D: MED is only compared between the same AS; it won't affect AS 500's choice.

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B (Reduce config complexity):Central controllers abstract policies, simplifying configuration.

C (Centralized IT functions):Controllers centralize management, automation, analytics, and assurance.

Other options explained:

A: Licensing varies but not universally inflated.

D: Failures are dependent on hardware design, not controller presence.

E: SDN does not inherently increase bandwidth usage.

Both FabricPath and TRILL are Layer 2 multipath technologies designed to eliminate spanning tree and allow for efficient forwarding across Layer 2 fabrics using routing techniques:

B (FabricPath permits active-active FHRP and TRILL supports anycast gateway):FabricPath (Cisco proprietary) integrates with vPC+ to allow active-active First Hop Redundancy Protocol (FHRP) operation at the access layer. This enables multiple default gateways to operate simultaneously, improving resiliency and utilization.TRILL (IEEE standard) uses anycast gateway functionality natively, where multiple switches share the same IP and MAC address for default gateway, allowing hosts to forward to any available gateway, providing active-active behavior at Layer 3.

Other options explained:

A: Incorrect — both FabricPath and TRILL are based on IS-IS for control plane operations; VXLAN is not part of TRILL.

C: Incorrect — both FabricPath and TRILL support ECMP (Equal Cost Multi-Path) to utilize multiple paths efficiently.

D: Incorrect — both technologies allow active-active forwarding at Layer 2.

This comparison highlights CCDE v3.1 design expertise in data center fabric architectures and control plane technologies.

During massive BGP update events (such as after a topology change), a route reflector may struggle processing both BGP updates and the resulting TCP acknowledgments required for reliable BGP session communication.

Increasing the hold queue size allows the router to buffer more packets waiting for processing (including TCP acknowledgments), helping the router handle bursts of BGP updates without dropping TCP segments or tearing down sessions.

This queue tuning is a well-known scalability optimization in CCDE v3.1 when designing route reflector clusters handling large-scale control plane updates.

Why other options are incorrect:

B & C: Adjusting buffer sizes does not directly address TCP acknowledgment backlog.

D: Keepalive timers control session liveliness, not update processing.

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DUMPS (Designated Unified Multiprotocol Redistribution Strategy) using single-point redistribution with route tagging ensures scalable, loop-free redistribution.

Route tags prevent redistributed routes from being re-advertised into the originating protocol, avoiding routing loops even with multiple paths.

Single-point redistribution simplifies operational complexity compared to multipoint redistribution.

Why other options are incorrect:

A, B, D: ACLs are not scalable for filtering redistributed routes in large networks. Tags provide better control.