CCNA Practice Test - 17

The Application layer (layer 7) of the OSI model provides network services directly to user applications and software. This layer includes protocols like HTTP, FTP, SMTP, and DNS that allow users to interact with the network through applications such as web browsers and email clients.

WiMAX (Worldwide Interoperability for Microwave Access) is defined in IEEE 802.16 and provides broadband wireless access with speeds and quality comparable to DSL and cable. It offers last-mile broadband connectivity and can cover large geographic areas, making it an alternative to wired broadband connections.

When a RIP router receives a route to a destination that it already has in its routing table, it compares the metrics. RIP only keeps the route with the lowest cost (fewest hops). If the received update has a higher cost than the existing entry, the update is ignored and the existing better route is retained.

Administrative distance is the criterion used by Cisco routers to select between routes learned from different routing protocols or sources. Each routing source has a default AD value (e.g., connected=0, static=1, EIGRP=90, OSPF=110, RIP=120). The route with the lowest AD is installed in the routing table, regardless of the routing protocol's metric.

When a link-state router receives a Link State Packet (LSP) from a neighbor, it immediately floods this LSP to all its other neighbors (except the one it received it from). This flooding ensures all routers quickly receive the same topology information. SPF calculation happens later, after the LSP is processed and added to the LSDB.

The IOS image is stored in flash memory, the contents in flash can be updated using a TFTP server.

For inter-VLAN routing, each subinterface must have the default gateway IP address for devices in that VLAN to use for routing. The physical interface itself typically does not need an IP address configured. While it's common practice to match subinterface numbers to VLAN IDs, this is not a technical requirement, and the no shutdown command is generally issued on the physical interface, not each subinterface.

The host 192.168.16.43/28 belongs to the subnet 192.168.16.32/28 (addresses 192.168.16.32 to 192.168.16.47). A /28 mask corresponds to a wildcard mask of 0.0.0.15. The ACL statement must use the network address (192.168.16.32) paired with the wildcard mask (0.0.0.15) to match all hosts in that subnet.

The DTE physical layer are network nodes such as routers, servers and switches. DCEs are internetworking devices located normally with the telecom carrier. The connection between DTE and DCE can only be via physical cabling.

PVST+ (Per-VLAN Spanning Tree Plus) runs a separate spanning tree instance for each VLAN. To make this work, the Bridge ID was modified to include the VLAN ID, allowing each VLAN to have a different root bridge if desired. This modification maintains backward compatibility while enabling per-VLAN spanning tree calculations. The Bridge ID still contains priority and MAC address, but the VLAN ID extension is what makes PVST+ possible.

After a collision, CSMA/CD's backoff algorithm has each device wait a random amount of time before attempting to retransmit. The device whose random backoff timer expires first gets priority to transmit - there is no inherent priority based on MAC address, IP address, or timing of the collision itself. This randomized approach helps prevent repeated collisions by ensuring devices don't all retry simultaneously.

A worm is a self-replicating malware that propagates across networks without requiring user interaction or a host program. Unlike viruses (which attach to files), Trojan horses (which disguise themselves as legitimate software), or man-in-the-middle attacks (which intercept communications), worms actively exploit vulnerabilities to spread automatically across network connections, making them particularly dangerous for network propagation.

CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) was developed specifically for wireless networks to overcome the media contention problem. In wireless environments, devices cannot detect collisions during transmission (hidden node problem), so CSMA/CA uses collision avoidance through random backoff timers and RTS/CTS mechanisms. It does not directly address bandwidth saturation, privacy, or device interoperability.

The wildcard mask 0.0.15.255 matches networks where the third octet ranges from 0 to 15. This means 192.168.0.0/24 through 192.168.15.0/24 will be advertised. The wildcard mask works by having 0 bits that must match exactly and 1 bits that can vary. The binary of 15 is 00001111, allowing the first 4 bits to match (giving 0-15) while the first two octets and last octet are fixed.