Network Fundamentals
Free Cisco Certified Network Associate (CCNA) practice — 6 questions on Network Fundamentals, with explanations. No sign-up. Full 12-question mixed test →
A network engineer is subnetting 192.168.20.0/24 using VLSM to support four LANs: Sales (100 hosts), Engineering (50 hosts), Guest (20 hosts), and a point-to-point WAN link (2 hosts). Which subnet mask should be assigned to the Engineering LAN to support exactly 50 hosts while minimizing wasted address space?
A /26 provides 2^6-2=62 usable host addresses, the smallest standard subnet size that satisfies the 50-host requirement, minimizing wasted addresses in a VLSM design.
A technician examines a Windows host's IPv6 configuration and finds the address FE80::A1B2:3C4D:5E6F:7A8B assigned to the network adapter with no default gateway populated for it. What best describes this address and its scope?
Addresses beginning with the FE80::/10 prefix are link-local, auto-generated on every IPv6-enabled interface, used for on-link functions like neighbor discovery, and never routed beyond the local segment.
An engineer is planning a 2.4 GHz wireless deployment with three access points placed to minimize co-channel interference. Which set of channels should be configured on the APs?
In the 2.4 GHz band, channels 1, 6, and 11 are the only non-overlapping 20 MHz channels in most regulatory domains, allowing adjacent APs to avoid co-channel and adjacent-channel interference.
A company is deploying a VoIP solution and needs to select the transport protocol for the real-time voice media stream (RTP), where minimizing latency is more important than guaranteeing delivery of every packet. Which characteristic makes the correct protocol the right choice for this traffic?
UDP is connectionless with no handshake, acknowledgments, or retransmissions, resulting in lower latency and overhead — ideal for real-time voice/video where a late packet is worse than a dropped one.
A data center architect needs a fabric where any two servers experience the same number of hops and predictable, low latency regardless of which leaf switches they attach to. Which topology BEST meets this requirement?
In a spine-leaf design, every leaf switch connects to every spine switch, so traffic between any two leaf-attached servers always crosses exactly one spine — giving equal, predictable hop count and non-blocking east-west bandwidth.
A service provider router hosts routing tables for multiple customers on the same physical device and must keep each customer's routes completely isolated from one another, even if customers use overlapping private IP address ranges. Which virtualization technology should be implemented on the router?
VRF creates multiple independent routing tables on a single router, allowing overlapping IP address spaces between customers while keeping their routes and forwarding decisions completely isolated — a core technique in MPLS/VPN service provider networks.
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