Foundational networking knowledge - OSI model, addressing, routing, operations, security, and troubleshooting - for the CompTIA Network+ N10-009 exam, with a worked explanation on every practice question.
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lock_openFree sampleNetworking Conceptshard
A network designer needs each subnet to provide exactly six usable host addresses, with no addresses wasted beyond the network and broadcast addresses. Which IPv4 prefix length meets this requirement?
- A/29check_circle Correct
- B/27
- C/28
- D/30
Usable hosts per subnet equal two raised to the host-bit count minus two, so a /29 with three host bits yields exactly six usable addresses. The usable-host count is two raised to the power of thirty-two minus the prefix, minus two for the all-zeros network address and the all-ones broadcast address. A /29 has three host bits, giving eight total and six usable.
Why A is correct: A /29 leaves three host bits, so two to the third power is eight addresses, and subtracting the network and broadcast addresses leaves exactly six usable hosts.
Why B is wrong: A /27 leaves five host bits, giving 32 addresses and 30 usable hosts; tempting if you stop at the host-bit field, but it is far larger than six.
Why C is wrong: A /28 leaves four host bits, giving 16 addresses and 14 usable hosts; tempting if you miscount by a single host bit, but it doubles the size needed.
Why D is wrong: A /30 leaves two host bits, giving four addresses and two usable hosts, the point-to-point size; tempting but it supplies only two hosts, not six.
lock_openFree sampleNetworking Conceptshard
A technician sees an interface auto-configure the address fe80::1a2b:3cff:fe4d:5e6f with no DHCP server present. Which statement about this address is correct?
- AIt is a global unicast address routable across the public internet.
- BIt is a link-local address valid within the local link and not forwarded by routers.check_circle Correct
- CIt is a unique local address intended for private site-wide routing.
- DIt is a multicast address used to reach a defined group of interfaces.
IPv6 addresses in the fe80::/10 range are link-local, auto-generated on each interface, and never forwarded by routers beyond their own link. The fe80::/10 prefix denotes link-local scope defined in RFC 4291. Such addresses form automatically for neighbour discovery and on-link communication, and routers must not forward them off the link.
Why A is wrong: Global unicast addresses begin 2000::/3 and are internet-routable; tempting because both are unicast, but the fe80 prefix confines this one to the local link.
Why B is correct: Addresses in fe80::/10 are link-local, generated automatically on every IPv6 interface, and routers do not forward them beyond the link on which they appear.
Why C is wrong: Unique local addresses use fc00::/7, commonly fd00::/8, for private routing within a site; tempting as a private analogue, but fe80 marks link-local, not ULA.
Why D is wrong: Multicast addresses begin ff00::/8 and target a group; tempting because IPv6 relies heavily on multicast, but fe80 is a unicast link-local address.
lock_openFree sampleNetworking Conceptshard
A Windows host fails to obtain a lease because no DHCP server responds, and it self-assigns an address so it can still communicate on the local segment. From which range does the host draw this address?
- A10.0.0.0/8, the largest RFC 1918 private block
- B172.16.0.0/12, an RFC 1918 private block
- C169.254.0.0/16, the IPv4 link-local blockcheck_circle Correct
- D192.168.0.0/16, an RFC 1918 private block
When DHCP fails, a host self-assigns an APIPA address from 169.254.0.0/16, which is distinct from the administrator-assigned RFC 1918 private ranges. APIPA, IPv4 link-local autoconfiguration, draws from 169.254.0.0/16 as defined in RFC 3927. It provides same-segment connectivity without a DHCP server and is separate from the RFC 1918 private ranges.
Why A is wrong: 10.0.0.0/8 is an RFC 1918 private range assigned by administrators or DHCP; tempting as private space, but hosts do not self-assign from it when DHCP fails.
Why B is wrong: 172.16.0.0/12 is an RFC 1918 private block used inside organisations; tempting because it is internal, but it is administrator-assigned, not the fallback range.
Why C is correct: APIPA uses 169.254.0.0/16, the IPv4 link-local block; a host self-assigns from it for same-segment connectivity only when no DHCP lease can be obtained.
Why D is wrong: 192.168.0.0/16 is the RFC 1918 range common in homes and small offices; tempting because DHCP often serves it, but a failed lease does not draw from it.
Frequently asked questions
- How many questions are on the N10-009 exam?
- The CompTIA Network+ (N10-009) exam has Maximum of 90 questions questions and runs for 90 minutes. The format is multiple choice and performance-based.
- What score do I need to pass N10-009?
- The pass mark is 720 / 900. Examworthy gives you a per-domain readiness score so you can see which domains are holding you back before you book.
- How much does the N10-009 exam cost?
- The exam costs 369 USD to sit. Practising on Examworthy is free to start, with a worked explanation on every question.
- Is there a N10-009 practice exam?
- Yes. Examworthy's exam mode runs a timed N10-009 practice exam (mock) paced to match the real exam, scored per domain so you can see exactly where you stand against the blueprint. Timed mocks are free with an account.
- How does Examworthy help me prepare for N10-009?
- Every practice question carries a worked explanation and a per-distractor rationale, mapped to the official blueprint domains. You learn why each answer is right or wrong, not just the letter.
- Is Examworthy affiliated with CompTIA?
- No. Examworthy is not affiliated with or endorsed by CompTIA. Our questions are original, blueprint-aligned practice material; we never reproduce live exam items.
Examworthy is not affiliated with or endorsed by CompTIA. All questions are original, blueprint-aligned practice material. We never reproduce live exam items. N10-009 and related marks belong to their respective owners.
