Cisco CCNA (200-301) — All Questions

Which layer of the OSI model is responsible for logical addressing and determining the best path to route packets between networks?

• a.Data Link (Layer 2)
• b.Transport (Layer 4)
• c.Network (Layer 3)✓
• d.Session (Layer 5)

The Network layer (Layer 3) handles logical addressing, such as IPv4 and IPv6, and performs routing to select the best path across internetworks. Routers operate at this layer. The Data Link layer uses physical MAC addresses within a single segment, while the Transport layer manages end-to-end delivery.

A host is configured with the IPv4 address 172.16.45.10/20. What is the network address of the subnet it belongs to?

• a.172.16.45.0
• b.172.16.32.0✓
• c.172.16.40.0
• d.172.16.0.0

A /20 mask (255.255.240.0) makes the third octet increment in blocks of 16 (256 - 240 = 16). The subnets in the third octet are 0, 16, 32, 48, so 45 falls in the 32 block, giving a network address of 172.16.32.0. The host portion is zeroed to identify the subnet.

Which IPv6 address type is automatically configured on every IPv6-enabled interface and is only valid within a single link (never routed)?

• a.Link-local (FE80::/10)✓
• b.Global unicast (2000::/3)
• c.Unique local (FC00::/7)
• d.Multicast (FF00::/8)

Link-local addresses in the FE80::/10 range are automatically generated on each IPv6 interface and are used for on-link communication such as neighbor discovery and next-hop routing. Routers never forward packets with link-local source or destination addresses beyond the local link. Global unicast addresses are the routable, Internet-facing addresses.

Which TCP/IP protocol provides connectionless, best-effort delivery with no retransmission or flow control, making it suitable for real-time voice traffic?

• a.TCP
• b.ICMP
• c.ARP
• d.UDP✓

UDP (User Datagram Protocol) is a connectionless Transport layer protocol that adds minimal overhead and does not guarantee delivery, ordering, or provide flow control. This low latency makes it ideal for real-time applications like VoIP and video streaming where speed matters more than retransmission. TCP, by contrast, is connection-oriented and reliable.