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Question 101

Which protocol is primarily used to synchronize the clocks of network devices?

1. NTP
2. SNMP
3. Syslog
4. DNS

Correct Answer: 1

Explanation

Network Time Protocol (NTP) synchronizes the clocks of network devices with a reliable time source. Accurate time is important for troubleshooting, security, logging, authentication, and event correlation. When multiple devices use synchronized clocks, administrators can more easily determine the sequence of events during an incident. NTP can use hierarchical time sources, with devices receiving time from higher-level servers and potentially providing it to other devices. Proper time synchronization is especially important when analyzing logs from multiple routers, switches, firewalls, and network-management systems.

Question 102

Which BGP attribute is normally preferred when selecting a route with the shortest AS path?

1. Local Preference
2. MED
3. Weight
4. AS Path

Correct Answer: 4

Explanation

The AS Path attribute records the autonomous systems that a BGP route has traversed. When comparing otherwise suitable BGP routes, a shorter AS Path is generally preferred. This mechanism also helps prevent routing loops because a BGP router rejects routes containing its own AS number. Administrators can influence path selection by manipulating AS Path information through techniques such as AS-path prepending. Although AS Path is an important BGP attribute, it is considered after several other attributes in the BGP best-path decision process.

Question 103

What is the primary function of a VLAN?

1. Logically separate a Layer 2 network into different broadcast domains
2. Encrypt Ethernet frames
3. Assign public IP addresses
4. Provide WAN connectivity

Correct Answer: 1

Explanation

A Virtual Local Area Network (VLAN) logically separates a switched network into different Layer 2 broadcast domains. Devices assigned to different VLANs are isolated at Layer 2 and generally require a Layer 3 device or routing function to communicate with each other. VLANs improve segmentation, organization, and security while allowing network administrators to group devices according to function rather than physical location. VLANs are identified using VLAN IDs, and trunk links can carry traffic for multiple VLANs between switches.

Question 104

Which OSPF LSA type is used to advertise networks within a normal area?

1. Type 3
2. Type 1
3. Type 5
4. Type 7

Correct Answer: 2

Explanation

OSPF Type 1 LSAs, called Router LSAs, are generated by every OSPF router and describe the router’s links, connected networks, and link states within an area. They remain within the originating OSPF area. Type 3 LSAs are Summary LSAs used by area border routers to advertise networks between areas. Type 5 LSAs describe external routes, while Type 7 LSAs are used for external routes within certain NSSA configurations. Understanding LSA types is important when troubleshooting OSPF databases and inter-area routing.

Question 105

Which protocol is used to bundle multiple physical Ethernet links into one logical connection?

1. EtherChannel
2. GRE
3. VRF
4. NAT

Correct Answer: 1

Explanation

EtherChannel combines multiple physical Ethernet interfaces into a single logical interface. This provides increased bandwidth and redundancy while simplifying Layer 2 or Layer 3 configuration. The bundled interfaces operate as one logical link from the perspective of many network protocols. EtherChannel can be negotiated using protocols such as LACP or, on Cisco devices, PAgP. The physical interfaces participating in the bundle generally need compatible configuration parameters. If a member link fails, traffic can continue through the remaining links, improving availability.

Question 106

Which QoS mechanism limits the transmission rate by dropping or remarking packets that exceed a configured rate?

1. Shaping
2. Classification
3. Policing
4. Queuing

Correct Answer: 3

Explanation

QoS policing monitors traffic against a configured rate and takes action when traffic exceeds the allowed level. Depending on the configuration, excess packets may be dropped or remarked with a different QoS value. Policing is commonly used to enforce bandwidth limits at network boundaries or service-provider connections. Traffic shaping differs because it generally buffers excess traffic and sends it later at a controlled rate. Classification identifies traffic, while queuing determines how traffic is handled when multiple packets compete for transmission resources.

Question 107

Which IPv4 address range is reserved for link-local addressing when DHCP or manual addressing is unavailable?

1. 127.0.0.0/8
2. 224.0.0.0/4
3. 169.254.0.0/16
4. 100.64.0.0/10

Correct Answer: 3

Explanation

The IPv4 range 169.254.0.0/16 is reserved for link-local addressing. Hosts may automatically assign themselves an address from this range when they cannot obtain a valid IPv4 address through DHCP and no suitable static configuration exists. Link-local addresses are intended for communication on the local Layer 2 segment and are not normally routed across IP networks. The 127.0.0.0/8 range is reserved for loopback, 224.0.0.0/4 is used for IPv4 multicast, and 100.64.0.0/10 is designated for carrier-grade NAT addressing.

Question 108

Which technology allows separate routing tables to exist on the same physical router?

1. VRF
2. STP
3. CDP
4. LACP

Correct Answer: 1

Explanation

Virtual Routing and Forwarding (VRF) allows multiple independent routing and forwarding tables to exist on the same physical device. Each VRF can maintain separate routes and interfaces, allowing traffic belonging to different customers, departments, or security domains to remain logically isolated. VRF is widely used in service-provider and enterprise environments where overlapping IP address spaces or strong routing separation are required. Unlike VLANs, which primarily provide Layer 2 segmentation, VRFs provide logical separation at the Layer 3 routing level.

Question 109

Which Cisco command is useful for viewing the current IPv4 routing table?

1. show ip route
2. show vlan brief
3. show cdp neighbors
4. show etherchannel summary

Correct Answer: 1

Explanation

The show ip route command displays the IPv4 routing table on a Cisco router or Layer 3 switch. It provides information about connected, static, and dynamically learned routes, including destination prefixes, next hops, administrative distances, metrics, and routing sources. This command is one of the most important tools for troubleshooting Layer 3 connectivity. Administrators can use it to determine whether a destination is known and which route the device considers the best path. Other commands provide VLAN, neighbor, or EtherChannel information instead.

Question 110

Which BGP attribute is commonly used to influence inbound traffic by advertising a less preferred path to external peers?

1. Local Preference
2. AS Path Prepending
3. Weight
4. Router ID

Correct Answer: 2

Explanation

AS Path prepending can influence inbound traffic by making an advertised route appear to have a longer AS path. When an organization prepends its own AS number multiple times to a route advertisement, external BGP routers may consider that path less attractive compared with another path having a shorter AS path. This technique is commonly used to influence how external networks enter an autonomous system. It should be applied carefully because actual BGP path selection also depends on other attributes and policies configured by remote networks.

Question 111

Which protocol is commonly used to send system messages from network devices to a centralized logging server?

1. NetFlow
2. Syslog
3. NTP
4. DHCP

Correct Answer: 2

Explanation

Syslog is commonly used to transmit system and event messages from network devices to centralized logging servers. These messages can contain information about interface changes, authentication events, configuration activity, system conditions, and other operational events. Centralized logging makes it easier for administrators to monitor multiple devices and investigate incidents. Syslog messages can have different severity levels, allowing organizations to determine which events should be stored or alerted on. Syslog complements monitoring technologies such as SNMP and telemetry by providing event-oriented information.

Question 112

Which OSPF feature allows an area to avoid receiving external Type 5 LSAs?

1. DR election
2. OSPF authentication
3. Stub area
4. Router ID

Correct Answer: 3

Explanation

An OSPF stub area is designed to reduce the amount of external routing information that an area must maintain. Stub areas do not receive Type 5 LSAs that describe external routes. Instead, an appropriate default route can be used to reach destinations outside the area. This can simplify the OSPF database and reduce routing information on routers with limited requirements. Other OSPF features serve different purposes: DR election manages multiaccess networks, authentication protects routing exchanges, and the Router ID uniquely identifies an OSPF router.

Question 113

What does the first field in an IPv4 packet’s TTL value primarily help prevent?

1. DNS failures
2. Layer 2 switching loops
3. Packets circulating indefinitely at Layer 3
4. Duplicate MAC addresses

Correct Answer: 3

Explanation

The IPv4 Time to Live (TTL) field prevents packets from circulating indefinitely through Layer 3 routing loops. Each router that forwards an IPv4 packet decreases the TTL value by at least one. When the value reaches zero, the router discards the packet and typically sends an ICMP Time Exceeded message to the source. This mechanism protects networks from wasting resources on packets trapped in routing loops. TTL is a Layer 3 function and is separate from Layer 2 mechanisms such as STP, which prevent Ethernet switching loops.

Question 114

Which protocol is commonly used to authenticate administrators against a centralized AAA server while encrypting the entire authentication exchange?

1. TACACS+
2. RADIUS
3. HTTP
4. FTP

Correct Answer: 1

Explanation

TACACS+ is a Cisco-supported AAA protocol that provides centralized authentication, authorization, and accounting for network-device administration. A major characteristic of TACACS+ is that it encrypts the entire body of the authentication packet, providing stronger protection for administrative access information. TACACS+ also separates authentication and authorization, allowing detailed control over administrator privileges. RADIUS is another widely used AAA protocol, particularly for network access, but it handles authentication and authorization differently. TACACS+ is commonly selected when granular administrative authorization is required.

Question 115

Which switching mechanism forwards a frame based on the destination MAC address?

1. IP routing
2. DNS resolution
3. MAC address table lookup
4. BGP policy

Correct Answer: 3

Explanation

A Layer 2 switch forwards Ethernet frames by examining the destination MAC address and consulting its MAC address table. The table associates learned MAC addresses with switch ports and VLANs. If the destination MAC is known, the switch forwards the frame through the corresponding interface. If the destination is unknown, the switch may flood the frame within the appropriate VLAN. MAC addresses are learned from source addresses of incoming frames. This Layer 2 forwarding process is different from IP routing, which uses destination IP prefixes.

Question 116

Which technology provides a secure encrypted tunnel between IP networks over an untrusted network?

1. VLAN
2. IPsec VPN
3. STP
4. EtherChannel

Correct Answer: 2

Explanation

IPsec VPNs provide secure communication across untrusted networks such as the public Internet. IPsec can provide confidentiality, integrity, authentication, and anti-replay protection depending on the selected security mechanisms and configuration. Site-to-site IPsec VPNs are commonly used to securely connect branch offices, data centers, or other networks. Remote-access VPNs can provide secure connectivity for individual users. VLANs and EtherChannel address network segmentation and link aggregation, while STP prevents Layer 2 loops. IPsec is specifically designed to protect IP traffic across insecure networks.

Question 117

Which protocol is used to dynamically negotiate an EtherChannel using an industry-standard method?

1. PAgP
2. LACP
3. VTP
4. CDP

Correct Answer: 2

Explanation

Link Aggregation Control Protocol (LACP) is an IEEE-standard protocol used to dynamically negotiate and maintain link aggregation. It allows compatible physical interfaces to form an EtherChannel when their configuration parameters are suitable. LACP provides interoperability between devices from different vendors, unlike Cisco proprietary PAgP. LACP uses active and passive modes to determine how channel negotiation occurs. Proper configuration of speed, duplex, VLAN settings, trunk parameters, and other relevant attributes is important because incompatible member interfaces may prevent the EtherChannel from forming correctly.

Question 118

Which IPv6 mechanism allows a host to discover the Layer 2 address associated with another IPv6 host?

1. DHCPv4
2. ARP
3. Neighbor Discovery
4. RARP

Correct Answer: 3

Explanation

IPv6 uses Neighbor Discovery Protocol (NDP) to perform functions that include discovering neighboring devices and resolving IPv6 addresses to corresponding Layer 2 addresses. NDP operates using ICMPv6 messages and replaces the traditional IPv4 ARP mechanism. Neighbor Solicitation and Neighbor Advertisement messages are particularly important for address resolution and neighbor communication. NDP also supports router discovery and duplicate address detection. Because IPv6 does not use ARP, troubleshooting IPv6 neighbor resolution requires understanding ICMPv6 and the Neighbor Discovery process.

Question 119

Which command can be used to verify the status and members of an EtherChannel on a Cisco switch?

1. show ip protocols
2. show etherchannel summary
3. show access-lists
4. show ip bgp

Correct Answer: 2

Explanation

The show etherchannel summary command provides a concise overview of EtherChannel groups and their member interfaces. It can help administrators determine whether a channel is formed correctly, which interfaces are participating, and whether ports are operating as expected. This command is especially useful when troubleshooting problems involving LACP, PAgP, or static EtherChannels. Other commands focus on routing protocols or access-control information. When an EtherChannel fails to form, administrators should also verify that member interfaces have compatible configurations.

Question 120

Which network design principle places access, distribution, and core functions into separate hierarchical layers?

1. Flat networking
2. Peer-to-peer networking
3. Hierarchical network design
4. Single-segment networking

Correct Answer: 3

Explanation

Hierarchical network design organizes enterprise networks into logical layers, traditionally including access, distribution, and core. The access layer connects end devices, the distribution layer provides policy enforcement and aggregation, and the core provides high-speed connectivity between major network sections. Separating functions improves scalability, manageability, redundancy, and troubleshooting. Not every modern network requires all three layers as separate physical tiers, but the hierarchical principles remain useful for designing resilient infrastructure. Proper layering also helps administrators identify where routing, security, and policy functions should be implemented.