Cisco Certified Network Associate (CCNA 200-301) practice questions

A host is automatically configuring a link-local IPv6 address with no router present on the segment. Which prefix identifies the address it generates, and what is the defining property of that address?

• Afe80::/10, valid only on the local link and never forwarded by a routercheck_circle Correct
• Bfc00::/7, routable within a single organisation but not on the public internet
• C2000::/3, globally routable and reachable across the public internet
• Dff00::/8, delivered to every interface that has joined the group

Why A is correct: Link-local addresses always come from the fe80::/10 range and an IPv6 router never forwards them off the link, so they remain confined to the local segment - this is the defining property the question asks for.

Why B is wrong: fc00::/7 is the unique local address (ULA) range, which is site-scoped and can be routed between internal subnets; it is not the prefix a host self-assigns for link-local communication, so it is the wrong classification here.

Why C is wrong: 2000::/3 is the global unicast range used for internet-reachable addresses; a host cannot mint a globally routable address without a router advertisement supplying the prefix, so this does not describe the no-router self-configured address.

Why D is wrong: ff00::/8 is the multicast range used for one-to-many delivery, not a unicast address a single host assigns to its own interface; it is a tempting confusion because both are auto-derived, but it is not link-local.

An interface with MAC address 00:1C:2D:AA:BB:CC builds its 64-bit interface identifier using modified EUI-64. Which interface identifier results?

• A001C:2DFF:FEAA:BBCC, splitting the MAC and inserting FFFE with the first octet unchanged
• B021C:2DFF:FEAA:BBCC, splitting the MAC, inserting FFFE, and flipping the seventh bit of the first octetcheck_circle Correct
• C001C:2DFE:FFAA:BBCC, inserting the bytes FEFF in the middle and leaving the first octet unchanged
• D031C:2DFF:FEAA:BBCC, inserting FFFE and flipping the eighth bit of the first octet

Why A is wrong: This correctly splits the MAC and inserts FFFE in the middle but skips flipping the universal/local bit, leaving the first octet as 00 instead of 02; that omitted bit-flip is the single most common modified EUI-64 mistake.

Why B is correct: Modified EUI-64 splits the OUI from the device portion, inserts FFFE between them, and inverts the seventh bit of the first octet (00 becomes 02), producing exactly 021C:2DFF:FEAA:BBCC.

Why C is wrong: The inserted value is FFFE, not FEFF; reversing those two bytes is a plausible slip but yields an invalid interface identifier, and this answer also fails to flip the universal/local bit.

Why D is wrong: The bit that modified EUI-64 inverts is the seventh bit, not the eighth; flipping the wrong bit turns 00 into 01 rather than 02, so 031C is wrong and so is the stated bit position.

A router learns the exact same prefix 192.168.20.0/24 from three sources at once: RIP, OSPF, and internal EIGRP. With default settings and no manual configuration changes, which route is installed in the routing table?

• AThe internal EIGRP route, because its administrative distance of 90 is the lowest of the threecheck_circle Correct
• BThe OSPF route, because OSPF uses cost based on bandwidth and is more accurate than EIGRP
• CThe RIP route, because RIP hop count gives the simplest and most reliable loop-free path
• DAll three routes, because the router load-balances equally across every protocol that offers the prefix

Why A is correct: When the prefix is identical, the router trusts the source with the lowest administrative distance; internal EIGRP at 90 beats OSPF at 110 and RIP at 120, so the EIGRP route is installed.

Why B is wrong: Metric quality is irrelevant across different protocols; selection here is by administrative distance, and OSPF at 110 is higher than internal EIGRP at 90, so OSPF is not preferred.

Why C is wrong: RIP carries the highest administrative distance of these three at 120, so it is the least trusted; its hop-count metric is never compared against the other protocols' metrics.

Why D is wrong: Routers do not load-balance across different protocols for one prefix; equal-cost load balancing only happens within a single protocol, so only the lowest-AD source is installed.