SkillTestPro | CCNP 300-420 ENSLD Practice Test 1

CCNP ENSLD 300-420 Practice Test 1 (Hard) - Structured IPv4/IPv6 Addressing & IS-IS Design

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1 / 10

When designing a structured IPv4 addressing plan for a multi-site enterprise using VLSM, what is the primary design benefit of allocating address blocks that align with the network's hierarchical topology (core/distribution/access)?

It automatically encrypts traffic between hierarchical layers

It allows all sites to share a single broadcast domain regardless of physical location

It removes the need for an addressing plan to account for future growth

It eliminates the need for any dynamic routing protocol between sites

It enables efficient route summarization at each hierarchical boundary, reducing the routing table size and improving convergence by containing topology changes within a smaller scope

It guarantees that no subnet will ever need to be resized in the future

2 / 10

In IS-IS design for a large enterprise campus, what is the primary design driver for implementing a multi-level (Level 1/Level 2) hierarchy rather than a single flat Level 2 area?

To allow the use of both IPv4 and IPv6 simultaneously, which a single-level design cannot support

To eliminate the need for a Designated Intermediate System on multi-access links

To enable route redistribution from OSPF without additional configuration

To limit the scope of SPF recalculation and LSP flooding to smaller areas, improving convergence and scalability as the network grows

To reduce the number of IS-IS routers required to run BGP

To allow each area to use a different Interior Gateway Protocol independently

3 / 10

An enterprise is designing an IS-IS network where Level 1 routers in remote sites need optimal (not just default) routing to multiple Level 2 exit points. Which design feature addresses this requirement?

Configuring wide metrics without enabling route leaking

Enabling IS-IS fast-flooding on Level 1 links only

Disabling the overload bit on all Level 2 routers

Enabling the 'attached bit' along with route leaking (redistributing selected Level 2 routes into Level 1) so Level 1 routers can make optimal exit-point decisions instead of relying solely on the nearest-attached-router default route

Configuring all routers as Level 1-2 to eliminate the hierarchy entirely

Increasing the IS-IS hello interval on Level 1 links

4 / 10

When designing an IPv6 addressing plan for an enterprise campus, what is the recommended practice regarding subnet prefix length for point-to-point links to balance efficiency and design consistency?

Using /128 for point-to-point links since only a single host address is ever needed

Using /64 for all point-to-point links to remain fully consistent with LAN segments, since IPv6 does not support smaller prefixes on point-to-point links

Using a /127 (or /126 in older designs) for point-to-point links is generally recommended over the wasteful default /64, while still keeping /64 for all LAN segments to preserve SLAAC/EUI-64 compatibility

Avoiding numbering point-to-point links entirely and relying solely on link-local addresses for routing adjacencies

Using /112 for point-to-point links to align with legacy IPv4 addressing conventions

Using /48 for point-to-point links to match the site prefix allocation

5 / 10

A network architect is designing structured summarization for an IS-IS network with discontiguous subnets at multiple sites. Which statement about IS-IS route summarization design is accurate?

IS-IS summarization is configured per level (e.g., 'summary-address' at the Level 1/Level 2 boundary on an L1/L2 router), and unlike EIGRP or OSPF, IS-IS has no concept of areas tied directly to interface configuration beyond the L1/L2 boundary itself

IS-IS summarization is automatically enabled by default at every Level 1/Level 2 boundary router

IS-IS summarization requires each summarized subnet to be contiguous with the router's directly connected interfaces only

IS-IS summarization can only be performed at the autonomous system boundary, never at internal level boundaries

IS-IS does not support route summarization under any circumstance

IS-IS requires manual configuration of a stub area, identical to OSPF, before summarization can be enabled

6 / 10

Which statement correctly describes why IS-IS is often favored over OSPF in networks planning a dual-stack IPv4/IPv6 design with a single, unified routing process?

IS-IS runs directly over the data link layer (CLNS) rather than over IP, allowing a single IS-IS process to carry both IPv4 and IPv6 routing information using separate address-family TLVs without requiring two separate protocol instances

IS-IS requires IPv6 to be translated into IPv4 before advertisement

IS-IS requires two completely separate processes for IPv4 and IPv6, identical to OSPFv2/OSPFv3, offering no advantage

IS-IS encapsulates all IPv6 traffic inside GRE tunnels automatically

IS-IS uses a completely different SPF algorithm for IPv6 than for IPv4, doubling CPU load unnecessarily

IS-IS cannot support IPv6 at all and requires OSPFv3 to be used alongside it

7 / 10

When creating a structured addressing plan, what is the design rationale for reserving distinct, non-overlapping IPv4 supernets per region/site rather than assigning addresses ad hoc as sites are added?

It removes the need for DHCP at any site

It is required because IPv4 addresses assigned ad hoc cannot be routed by any dynamic routing protocol

It is only relevant for IPv6 designs and has no bearing on IPv4 addressing

It allows every site to use the identical IP subnet without conflict

It preserves the ability to summarize each region's routes at the regional boundary as the network scales, preventing routing table bloat and simplifying policy application (e.g., filtering by supernet)

It guarantees that NAT will never be required anywhere in the design

8 / 10

An architect is designing IS-IS metrics for a network with links of varying bandwidth (1G, 10G, 100G). Using the classic narrow metric (max value 63) would cause which specific design problem, and what is the recommended solution?

Narrow metrics cannot adequately differentiate between high-bandwidth links, causing suboptimal path selection; the recommended solution is to enable wide metrics (32-bit, via 'metric-style wide'), which allows a much larger range of values to accurately reflect bandwidth differences

Narrow metrics cause the IS-IS adjacency to fail to form on any link above 1 Gbps

Narrow metrics cause every route to be assigned the same cost automatically, requiring manual per-route override

The solution is to disable metric usage entirely and rely solely on hop count

Narrow metrics are only a concern for OSPF, not IS-IS, since IS-IS metrics are always automatically calculated from bandwidth

The only solution is to migrate away from IS-IS entirely to a protocol with wider metrics

9 / 10

When designing route summarization boundaries for a large enterprise with both IS-IS and BGP in use (IS-IS as IGP, BGP for site-to-site VPN overlay), what design principle should govern where prefixes are summarized?

Summarization boundaries are irrelevant to convergence time in any protocol

Summarize IGP (IS-IS) routes at natural hierarchical boundaries (area/level edges) to control IGP table size and convergence scope, while carefully considering that overly aggressive summarization at BGP redistribution points can create suboptimal routing or blackholes if the summarized range includes unreachable subnets

Summarization should never be performed anywhere BGP is present, since BGP and IGP summarization are mutually exclusive

IS-IS and BGP cannot coexist within the same enterprise network design

BGP automatically re-summarizes any IS-IS routes redistributed into it without any configuration

IS-IS summarization must exactly match BGP's AS-path length to function correctly

10 / 10

What is a key design consideration when deciding whether to use a single flat IS-IS Level 2 area versus a hierarchical Level 1/Level 2 design for a growing enterprise campus network?

A flat design is always preferred because hierarchical designs cannot support redundant links between areas

Hierarchical IS-IS designs require a completely separate physical network for each level

A flat Level 2-only design is simpler to manage initially but does not scale well as the number of routers/links grows, since every router must run SPF over the entire topology; a hierarchical design trades some complexity for improved scalability and fault isolation as the network grows

A flat design automatically summarizes routes, making hierarchical design unnecessary

A hierarchical design is only useful for OSPF and provides no benefit in IS-IS

There is no scalability difference between flat and hierarchical IS-IS designs

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