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Question 81
An organization wants to implement a wireless security solution that provides individual encryption keys for each client. Which authentication method should be used?
A) WEP with 128-bit keys
B) WPA2-Personal with PSK
C) WPA2-Enterprise with 802.1X
D) Open authentication with MAC filtering
Answer: C
Explanation:
WPA2-Enterprise with 802.1X is the wireless security solution that provides individual encryption keys for each client, delivering the highest level of security for enterprise wireless networks. This authentication method uses a RADIUS server for centralized authentication and generates unique encryption keys for every client session. It effectively ensures that each client has a distinct session, which is vital for maintaining confidentiality and data integrity across a large network. Given the increasing complexity and sophistication of cyber threats, WPA2-Enterprise provides a more robust and scalable security mechanism compared to other wireless security protocols.
The WPA2-Enterprise implementation works by using 802.1X for authentication, where each client must provide individual credentials before gaining network access. 802.1X is an IEEE standard for network access control, and its use in WPA2-Enterprise ensures that only authorized users or devices can access the wireless network. When a client successfully authenticates through the RADIUS server, the access point and client derive unique Pairwise Transient Keys (PTK) for that specific session. These keys are used to encrypt all data transmitted between the client and access point, ensuring that even if one client’s keys are compromised, other clients remain secure. The use of unique PTKs for each session prevents the risk of an attacker gaining access to multiple users’ data, even if they are able to intercept one session’s key.
The process begins when a client associates with an access point. Initially, the client is placed in an unauthenticated state, meaning it can only communicate with the access point using specific traffic designated for 802.1X authentication. During this phase, no user data can be exchanged, and the client’s device cannot access any network resources. To authenticate, the client presents its credentials through an Extensible Authentication Protocol (EAP) method, such as EAP-TLS, EAP-TTLS, or PEAP. These are common methods used in WPA2-Enterprise environments, each offering different levels of security and suitability based on the type of network and organizational needs.
Once the client sends its authentication request, the EAP message is forwarded by the access point to the RADIUS server. The RADIUS server then validates the credentials against its authentication database. If the credentials are valid, the server sends a master key back to the access point, which is used to derive session-specific keys for encryption. These keys, derived through a four-way handshake, are then shared between the client and access point, ensuring that both parties can encrypt and decrypt the communication during the session. The four-way handshake ensures that both the client and access point independently generate the same encryption keys without transmitting them directly, making the process resistant to eavesdropping.
Compared to legacy security protocols like WEP and WPA2-Personal, WPA2-Enterprise provides a significantly stronger defense against attacks. WEP with 128-bit keys uses a static shared key for all clients, and this key is the same across all users on the network. The shared key structure is inherently vulnerable to attacks such as key reuse and brute-force attempts. As the encryption key is static, an attacker who obtains the key can potentially decrypt any data on the network. WPA2-Personal with Pre-Shared Keys (PSK) also has limitations, as it uses the same key for every device. Once an attacker gains access to the pre-shared key, they can easily infiltrate the network, gaining access to sensitive data from all connected users. In contrast, WPA2-Enterprise’s dynamic key generation ensures that individual sessions remain isolated and much more difficult to exploit.
Another security concern with simpler wireless security methods like WEP and WPA2-Personal is that they do not offer centralized management, auditing, or fine-grained access control. This lack of control makes it challenging to monitor network activity and enforce strict security policies. With WPA2-Enterprise, the centralized RADIUS server allows administrators to enforce policies based on specific user credentials, roles, and devices. This enables organizations to restrict access to sensitive resources, segment the network based on user or device groupings, and track network usage through detailed auditing logs. The ability to enforce policies dynamically based on user identity and device type helps ensure that only authorized devices can access specific parts of the network.
WPA2-Enterprise also provides an enhanced level of protection against certain types of attacks, including man-in-the-middle (MITM) attacks, where an attacker intercepts communications between the client and access point. Because the encryption keys are unique to each session and are generated during the authentication process, an attacker who intercepts the network traffic cannot easily decrypt it. The use of dynamic encryption keys and a secure handshake makes it far more difficult for unauthorized users to impersonate the client or the access point, further strengthening the security of the network.
Moreover, WPA2-Enterprise is ideal for organizations that need to accommodate a large number of users, as it can scale effectively to meet the demands of different user types and access scenarios. Whether the network is supporting a small office environment or a large campus with thousands of users, WPA2-Enterprise can manage the authentication process and enforce security policies consistently. It is particularly beneficial in environments where users need to access the network on a frequent basis and where accountability is important, such as in government agencies, healthcare institutions, and financial services organizations.
For further enhancement of security, WPA2-Enterprise can also integrate with other technologies like VPNs, multi-factor authentication (MFA), and device management systems. For instance, when combined with VPNs, the communication between users and the network can be further encrypted, providing an additional layer of security. Similarly, multi-factor authentication ensures that even if a user’s credentials are compromised, the attacker would still need to provide additional information, such as a one-time password or biometric factor, to gain access. By integrating WPA2-Enterprise with modern authentication practices, organizations can create a multi-layered defense strategy that reduces the risk of unauthorized access.
However, despite its strong security capabilities, WPA2-Enterprise does come with some implementation challenges. First, it requires a more complex setup than simpler protocols like WPA2-Personal, as it depends on a RADIUS server and the configuration of EAP methods. Administrators must ensure that the RADIUS server is properly configured and maintained, and that all client devices are compatible with the chosen EAP methods. Moreover, because the protocol relies on digital certificates for authentication, organizations must carefully manage and distribute certificates to clients and ensure that they are kept secure.
The deployment of WPA2-Enterprise also typically involves the use of a centralized authentication and management system that may require additional infrastructure, such as directory services like Microsoft Active Directory, which adds an overhead in terms of cost and administration. Additionally, device compatibility can sometimes be an issue if older devices do not support the required EAP methods or WPA2-Enterprise standards.
Despite these challenges, the benefits of WPA2-Enterprise far outweigh its drawbacks for most organizations. The combination of robust encryption, individual client session keys, centralized management, and scalable access control make it the ideal choice for environments that demand high security, compliance with regulatory requirements, and strong user accountability. WPA2-Enterprise ensures that sensitive data transmitted over the wireless network remains protected and that only authorized individuals are granted access to the network’s resources. This makes it indispensable for organizations that prioritize network
Question 82
Which command verifies the OSPF neighbor relationships and displays the neighbor router ID, priority, state, and interface?
A) show ip ospf interface
B) show ip ospf neighbor
C) show ip ospf database
D) show ip protocols
Answer: B
Explanation:
The show ip ospf neighbor command is one of the most valuable tools for verifying OSPF (Open Shortest Path First) neighbor relationships in a router’s OSPF configuration. By providing detailed information about the state of OSPF adjacencies, this command helps network administrators ensure that OSPF is operating correctly and can also assist in troubleshooting any issues with neighbor relationships that might arise in a dynamic network environment.
When executed, the show ip ospf neighbor command displays a table with key details about each OSPF neighbor. This table includes columns for Router ID, Priority, State, Dead Time, Neighbor Address, and the local Interface used to reach that neighbor. Understanding each of these components is crucial for interpreting the command’s output and diagnosing potential problems with OSPF adjacency formation or stability.
The Router ID column identifies each OSPF neighbor by its router ID, which is the unique identifier OSPF uses for routers in an OSPF domain. This router ID is either the highest IP address of any of the router’s loopback interfaces or the highest IP address of an active interface on the router. Having this in the table allows administrators to easily confirm which router the neighbor is associated with. If the router IDs are incorrect or mismatched, it may indicate a configuration issue or even a potential routing problem.
The Priority column reflects the OSPF priority value, which is used in the election of the Designated Router (DR) on multi-access networks, such as Ethernet. A higher priority increases the likelihood that a router will be elected as the DR or Backup Designated Router (BDR). If OSPF is not behaving as expected in a network segment, checking the priority value can reveal whether the DR election process is happening correctly or whether there are misconfigurations that might affect network performance.
The State column is crucial for determining the current state of each OSPF neighbor relationship. The typical states you will see here include:
FULL: This is the desired state for fully formed adjacencies, meaning the OSPF routers have exchanged all required LSAs (Link-State Advertisements) and are fully synchronized.
2WAY: This is a normal state for routers on non-Designated Router (non-DR) or non-Backup Designated Router (non-BDR) interfaces in multi-access networks, like Ethernet. It indicates that two routers have successfully exchanged hello packets but have not yet completed the full OSPF handshake.
If a neighbor relationship is not in the FULL state when it should be, it typically indicates an issue such as mismatched OSPF parameters (e.g., hello and dead timers), mismatched authentication settings, or network connectivity issues.
The Dead Time field displays a countdown timer that shows how much time is left before the router considers the neighbor down if no Hello packets are received. This timer is crucial because OSPF depends on these periodic Hello packets to confirm the ongoing status of a neighbor. If the Dead Time reaches zero, the neighbor relationship will be declared as down, and OSPF will begin the process of re-establishing the adjacency. Monitoring this timer can help diagnose issues related to network congestion, interface failures, or improperly configured timers.
The Neighbor Address field shows the IP address of the neighboring router’s interface. This allows network administrators to verify that the correct neighbors are being discovered and that they are reachable via the appropriate interfaces. If there are inconsistencies in this field, it could point to problems like incorrect IP addressing or routing configuration errors.
The Interface column displays the local interface through which the router is communicating with the neighbor. This is helpful for identifying whether OSPF is using the correct interfaces for neighbor formation. Misconfigurations, such as OSPF not being enabled on the correct interfaces or interface shutdowns, can prevent OSPF adjacencies from forming properly, and this column can help identify such issues.
While show ip ospf neighbor provides valuable information about OSPF adjacencies, it’s important to remember that other commands can complement this one to give a fuller picture of OSPF performance and status. For example, the show ip ospf interface command provides OSPF-specific statistics about each interface, such as OSPF hello and dead intervals, and can indicate whether the interface is participating in OSPF. However, this command does not show actual neighbor relationships, so it needs to be used alongside show ip ospf neighbor to get a complete understanding of OSPF operation.
The show ip ospf database command provides information about the link-state database, showing the LSAs that OSPF routers exchange to build their routing tables. While this is useful for understanding the topology of the OSPF network and diagnosing routing issues, it does not provide information about OSPF neighbor states or active adjacencies, which is why show ip ospf neighbor is preferred when troubleshooting OSPF adjacency problems.
The show ip protocols command is another useful command that displays a summary of the routing protocols configured on the router, including OSPF. While it provides a summary of the protocol’s settings, including timers and networks being advertised, it doesn’t give detailed information about the router’s OSPF neighbors. For in-depth analysis of OSPF neighbors and their states, show ip ospf neighbor is far more effective.
The show ip ospf neighbor command is essential for diagnosing and troubleshooting OSPF neighbor relationship issues. It is particularly helpful when neighbors are not appearing as expected or when the state of the neighbor relationship is stuck in a non-ideal state, such as 2WAY or EXSTART, rather than progressing to FULL. In such cases, checking for common issues such as mismatched Hello and Dead intervals, incorrect network types (e.g., point-to-point vs. multi-access), or authentication failures can often resolve the issue. Misconfigurations related to OSPF area types, like ensuring all routers in an area are using the same area type, can also lead to adjacency problems that will be revealed by this command.
Question 83
A company needs to implement a solution that allows wireless clients to seamlessly move between access points while maintaining the same IP address. Which feature must be configured?
A) Lightweight Access Point Protocol (LWAPP)
B) Controller-based Architecture with Mobility Groups
C) Autonomous AP Mode
D) FlexConnect Local Switching
Answer: B
Explanation:
Controller-based architecture with Mobility Groups provides a robust and scalable solution for enabling wireless clients to seamlessly roam across multiple access points (APs) while retaining their IP addresses, even as they move between different wireless LAN controllers (WLCs). This architecture is especially critical in enterprise environments where users rely on wireless mobility, such as in large campuses, warehouses, or corporate offices, to maintain uninterrupted connectivity across expansive areas. By supporting seamless client handoffs from one AP to another without losing session information or requiring re-authentication, this system ensures a smooth and consistent user experience.
In a controller-based wireless architecture, Wireless LAN Controllers (WLCs) play a central role in managing access points. These controllers handle several key responsibilities, including client authentication, security policy enforcement, network configuration, and mobility management. Rather than configuring each AP individually, WLCs enable centralized management, making it easier to deploy, monitor, and maintain large-scale wireless networks. The mobility capabilities of this architecture are particularly beneficial in environments where users need to roam freely across the network without experiencing interruptions.
When multiple WLCs are configured as part of the same Mobility Group, they share important information about client sessions, allowing clients to roam from one AP to another, even across different controllers, without losing connectivity. This functionality is critical for users moving between APs in different areas of the network, such as from one building to another or across floors in a large office complex. The mobility group ensures that the client’s session remains intact, including the client’s IP address, authentication status, and any other context necessary for seamless roaming.
The process of roaming between controllers involves the exchange of mobility messages. When a client moves to an AP managed by a different controller, the new controller detects the client’s presence and sends a query to other controllers in the mobility group to locate the client’s “anchor” controller. The anchor controller is the one that originally authenticated the client and holds session information for the client’s connection. Once located, the anchor controller continues to manage the client’s session, but it tunnels the client’s traffic to the new controller, allowing the client to keep the same IP address even though the client is physically connected to a different AP or subnet. This tunneling process helps ensure that the client does not need to re-establish its session or re-authenticate, thus maintaining uninterrupted service as the client moves.
This mobility functionality is enabled through protocols such as the Lightweight Access Point Protocol (LWAPP). LWAPP is the communication protocol between the APs and controllers, providing mechanisms for configuration, control, and management of APs. However, while LWAPP facilitates communication and control between the APs and the controller, it does not directly provide mobility features. Instead, it is the Mobility Group feature within the controller architecture that enables inter-controller mobility. Without mobility groups, clients would lose their sessions and require re-authentication every time they roamed to a different AP, which would result in a poor user experience, especially in high-density environments with lots of roaming.
In contrast to controller-based architectures, autonomous APs operate independently, each requiring individual configuration and management. Autonomous APs do not rely on a central controller and do not offer the seamless roaming and mobility features of a controller-based system. Each AP must be configured manually, and the client device must establish a new session every time it roams to a different AP. This lack of coordination between APs makes autonomous APs unsuitable for environments where clients frequently move around, as they do not support features like session persistence or inter-AP handoff.
Question 84
Which IPv6 address type is used for one-to-one communication between specific interfaces?
A) Multicast
B) Anycast
C) Unicast
D) Broadcast
Answer: C
Explanation:
Unicast addresses in IPv6 are used for one-to-one communication between specific interfaces, making them the most common type of addressing for typical network communications. A packet sent to a unicast address is delivered to a single interface identified by that address, and this form of addressing is ideal for standard client-server communications, peer-to-peer connections, and a wide range of network applications. Essentially, IPv6 unicast addresses facilitate direct communication between two devices, providing reliable and efficient data transmission between them.
IPv6 unicast addresses are divided into several subtypes, each serving a specific purpose. One of the most widely used subtypes is global unicast addresses (GUAs), which are routable on the public internet. These addresses are globally unique and are assigned by regional internet registries (RIRs), ensuring that they do not conflict with addresses from other networks. The address block for global unicast addresses begins with the prefix 2000::/3. These addresses enable devices to be reachable from anywhere on the internet, providing a similar function to public IP addresses in IPv4.
Another subtype of IPv6 unicast addresses is unique local addresses (ULAs), which are used for private networks. These addresses are analogous to the private address space defined by RFC 1918 in IPv4 (such as 192.168.x.x and 10.x.x.x). ULAs are not routed on the global internet but can be used for communication within an organization’s internal network or between networks using tunneling mechanisms. Unique local addresses help maintain privacy and reduce the need for globally routable IP addresses, but they are not intended for public internet traffic.
Additionally, link-local addresses are a special type of unicast address in IPv6 that are automatically configured on all interfaces that support IPv6. These addresses are used for communication within a local subnet and are crucial for various IPv6 operations, such as neighbor discovery (ND) and router advertisements (RA). Link-local addresses always begin with the prefix FE80::/10 and can only be used for communication between devices on the same local network. They are not routable beyond the local network segment, and their primary role is to enable devices to discover each other and configure their addresses without needing external routers or DNS.
The structure of IPv6 unicast addresses is designed to support an immense address space, offering 128-bit addresses. This is in stark contrast to the 32-bit address space of IPv4, enabling IPv6 to support approximately 340 undecillion unique addresses. The large address space of IPv6 addresses essentially eliminates the need for techniques such as network address translation (NAT) in most scenarios, allowing for true end-to-end connectivity between devices. The first 64 bits of the address typically represent the network prefix, which identifies the subnet, while the remaining 64 bits are used to uniquely identify an interface on that subnet. This interface identifier is often derived from the device’s MAC address using the EUI-64 format, although it can also be randomly generated to enhance privacy and reduce tracking of devices.
Option A is incorrect because multicast addresses are used for one-to-many communication, where a single packet is sent to multiple devices that have subscribed to a multicast group. In contrast to unicast, which involves communication between two specific devices, multicast enables efficient distribution of data to multiple recipients, such as streaming media or group communication applications.
Option B is incorrect because anycast addresses are used for one-to-nearest communication. A packet sent to an anycast address is delivered to the nearest interface among a group of interfaces that share the same address, typically selected based on routing metrics such as hop count or latency. Anycast is primarily used for load balancing, redundancy, and optimizing network traffic by directing packets to the closest or most responsive server.
Option D is also incorrect because IPv6 does not use broadcast addresses at all. In IPv4, broadcast addresses were used to send data to all devices on a network, but in IPv6, broadcast functionality has been replaced with multicast addressing. This change improves efficiency by allowing devices to send data to only those nodes that are interested in receiving it, reducing network congestion and ensuring that only relevant devices receive certain types of traffic.
In summary, IPv6 unicast addresses provide the foundation for most typical network communication, offering various subtypes like global unicast, unique local addresses, and link-local addresses, each serving a specific purpose in different network scenarios. With its large address space, IPv6 simplifies addressing, eliminates the need for NAT in most cases, and supports seamless end-to-end connectivity for devices across the globe. Understanding the differences between unicast, multicast, anycast, and broadcast addresses is essential for network professionals to configure and troubleshoot IPv6 networks effectively.
Question 85
An administrator needs to configure a router to prevent routing loops by limiting the number of hops a packet can traverse. Which field in the IP header accomplishes this?
A) Header Checksum
B) Time to Live (TTL)
C) Fragment Offset
D) Protocol
Answer: B
Explanation:
The Time to Live field in the IP header is specifically designed to prevent routing loops by limiting the number of hops a packet can traverse through the network. Each router that forwards a packet decrements the TTL value by one, and when the TTL reaches zero, the router discards the packet and sends an ICMP Time Exceeded message back to the source.
The TTL mechanism provides critical protection against packets circulating indefinitely in the network due to routing loops caused by misconfiguration, routing protocol convergence issues, or redistribution problems. Without TTL, a routing loop would cause packets to traverse the same path repeatedly, consuming bandwidth and router resources until the network becomes congested or devices fail. The default TTL value varies by operating system, with most systems using values between 64 and 255 hops.
This field serves multiple purposes beyond loop prevention. Network diagnostic tools like traceroute rely on TTL manipulation to discover the path packets take through the network. Traceroute sends packets with incrementally increasing TTL values, forcing each successive router to respond with an ICMP Time Exceeded message, thereby revealing the route. The TTL value can also provide rough estimates of network distance, as a significantly decremented TTL indicates the packet has traversed many routers.
Option A is incorrect because the Header Checksum verifies the integrity of the IP header but does not prevent routing loops. Option C is incorrect because Fragment Offset is used for IP packet fragmentation and reassembly, indicating where a fragment belongs in the original packet. Option D is incorrect because the Protocol field identifies the upper-layer protocol encapsulated in the IP packet, such as TCP, UDP, or ICMP, and has no role in loop prevention.
Question 86
Which Cisco technology allows network administrators to create virtual network segments that share the same physical infrastructure while maintaining logical separation?
A) VRF
B) GRE Tunnel
C) Port Channel
D) Stack-Wise
Answer: A
Explanation:
Virtual Routing and Forwarding is the Cisco technology that enables network administrators to create multiple virtual network segments on the same physical infrastructure while maintaining complete logical separation between them. Each VRF instance maintains its own independent routing table, forwarding table, and set of interfaces, effectively creating multiple virtual routers within a single physical device.
VRF technology is commonly deployed in service provider environments where multiple customers must share the same physical infrastructure while keeping their traffic completely isolated. Each customer’s traffic is assigned to a separate VRF instance, ensuring that routing information and data packets never mix between different customers. This approach eliminates the need for dedicated routers for each customer, significantly reducing hardware costs and management complexity while maintaining the security and independence of separate networks.
The implementation of VRF involves assigning interfaces to specific VRF instances, configuring routing protocols within each VRF context, and optionally using route targets and route distinguishers when implementing MPLS VPN services. Enterprise organizations also leverage VRF for network segmentation, separating departments, isolating management traffic, or creating distinct paths for different types of traffic. Each VRF operates independently, with its own routing decisions based solely on the routes within that VRF instance.
Option B is incorrect because GRE tunnels create point-to-point connections over IP networks but do not provide the comprehensive virtualization and routing table separation that VRF offers. Option C is incorrect because Port Channel aggregates multiple physical links into a single logical link for increased bandwidth and redundancy, not network segmentation. Option D is incorrect because Stack-Wise is a Cisco technology for physically stacking multiple switches into a single logical unit, providing management simplification rather than network virtualization.
Question 87
A network engineer needs to configure dynamic trunk negotiation between two switches. Which protocol handles automatic trunk formation?
A) VTP
B) DTP
C) STP
D) CDP
Answer: B
Explanation:
Dynamic Trunking Protocol is the Cisco proprietary protocol specifically designed to handle automatic trunk negotiation between switches, enabling ports to dynamically determine whether to form trunk links without manual configuration. DTP automates the process of establishing trunk connections by exchanging negotiation frames between neighboring switches to agree on the trunking mode.
DTP operates by sending frames every 30 seconds on all ports configured for dynamic trunk negotiation. These frames advertise the port’s trunking capability and desire to form a trunk. When two switches with DTP-enabled ports connect, they negotiate based on their configured modes. The protocol supports several modes including dynamic desirable which actively attempts to form trunks, dynamic auto which forms trunks only if the neighbor is set to trunk or desirable, trunk mode which unconditionally forms trunks, and access mode which never forms trunks.
The negotiation process considers the administrative modes configured on both ends of the link. If one port is set to dynamic desirable and the other to dynamic auto, trunk, or dynamic desirable, a trunk will form. However, if both ports are set to dynamic auto, they will not form a trunk because neither is actively initiating trunk formation. Understanding these mode combinations is essential for properly configuring switch interconnections and avoiding unexpected behavior.
Option A is incorrect because VTP manages VLAN database synchronization across multiple switches but does not handle trunk negotiation. Option C is incorrect because STP prevents layer 2 loops by blocking redundant paths but does not negotiate trunk formation. Option D is incorrect because CDP discovers directly connected Cisco devices and shares information about them but does not perform trunk negotiation, though DTP frames are sent as CDP packets.
Question 88
Which OSPF network type requires manual neighbor configuration and does not elect a designated router?
A) Broadcast
B) Point-to-Point
C) Non-Broadcast
D) Point-to-Multipoint
Answer: C
Explanation:
The Non-Broadcast network type in OSPF requires manual neighbor configuration and elects both a Designated Router and Backup Designated Router, making it suitable for non-broadcast multi-access networks like Frame Relay and ATM where multicast and broadcast capabilities are not available. Administrators must explicitly configure neighbor statements for each OSPF peer because the network cannot automatically discover neighbors through multicast hello packets.
In Non-Broadcast mode, OSPF treats the network as a multi-access segment similar to Ethernet, meaning it follows the DR and BDR election process to reduce adjacency requirements and LSA flooding. The DR becomes adjacent with all other routers on the segment, while non-DR routers form adjacencies only with the DR and BDR. This behavior optimizes OSPF operation on networks with multiple routers sharing the same subnet but requires careful configuration to ensure proper DR election and neighbor relationships.
Configuration of Non-Broadcast networks requires using the neighbor command under the OSPF process to specify the IP address of each neighbor router. Additionally, administrators typically need to configure OSPF priority values to control which router becomes the DR, as the default election process may not produce desired results on non-broadcast networks. The hello and dead intervals default to 30 and 120 seconds respectively, longer than other network types to accommodate the typical characteristics of non-broadcast networks.
Option A is incorrect because Broadcast networks automatically discover neighbors using multicast and elect a DR and BDR. Option B is incorrect because Point-to-Point networks automatically form adjacencies between two routers without requiring manual neighbor configuration or DR election. Option D is incorrect because Point-to-Multipoint networks automatically discover neighbors, do not elect a DR, and treat each neighbor relationship as a separate point-to-point connection.
Question 99
An organization wants to implement automated network monitoring that can detect anomalies and predict potential failures before they occur. Which technology should be deployed?
A) Syslog
B) SNMP Polling
C) Network Assurance
D) NetFlow
Answer: C
Explanation:
Network Assurance is the advanced technology that provides automated network monitoring with the capability to detect anomalies and predict potential failures before they impact operations. This technology leverages machine learning algorithms, telemetry data, and artificial intelligence to analyze network behavior patterns and identify deviations that may indicate emerging problems.
Network Assurance continuously collects data from network devices using streaming telemetry, which provides real-time visibility into device operations with much higher frequency than traditional polling methods. The system establishes baselines for normal network behavior by analyzing historical data and current operations. When network metrics deviate from established patterns, the assurance engine generates alerts and provides insights into potential root causes, often before end users experience any service degradation.
The technology integrates with intent-based networking platforms like Cisco DNA Center, correlating data from multiple sources including device configurations, performance metrics, and user experience data. Network Assurance can identify issues such as configuration drift where device settings diverge from intended policies, capacity constraints before they cause performance problems, and security policy violations. The predictive capabilities help administrators transition from reactive troubleshooting to proactive network management.
Option A is incorrect because Syslog provides event logging and notification but does not perform anomaly detection or predictive analysis. Option B is incorrect because SNMP Polling collects device statistics periodically but lacks the intelligence for pattern analysis and prediction. Option D is incorrect because NetFlow analyzes traffic flows and provides visibility into bandwidth usage but does not offer comprehensive anomaly detection or failure prediction across all network parameters.
Question 100
Which command displays the MAC address table on a Cisco switch including the VLAN, MAC address, type, and ports?
A) show vlan brief
B) show mac address-table
C) show interfaces status
D) show cdp neighbors
Answer: B
Explanation:
The show mac address-table command displays comprehensive information about the switch’s MAC address table, including the VLAN association, MAC address, entry type, and the physical port where each MAC address was learned. This command is essential for troubleshooting connectivity issues, verifying proper MAC learning, and identifying which devices are connected to which switch ports.
The MAC address table output shows several important columns including the VLAN number indicating which VLAN the MAC address belongs to, the MAC address in hexadecimal format, the type field indicating whether the entry is dynamic or static, and the ports field showing the interface where the MAC address was learned. Dynamic entries are learned automatically through normal switch operation and age out after a period of inactivity, while static entries are manually configured and never age out.
Understanding the MAC address table is fundamental to troubleshooting layer 2 connectivity problems. If a MAC address does not appear in the table, the switch has not received any frames from that device, suggesting physical connectivity issues, wrong VLAN configuration, or device problems. If a MAC address appears on an unexpected port, it might indicate a cabling error, unauthorized device connection, or the presence of another switch between the device and the switch being examined.
Option A is incorrect because show vlan brief displays VLAN configuration and which ports are assigned to each VLAN but does not show the MAC addresses learned on those ports. Option C is incorrect because show interfaces status displays port status, VLAN assignment, speed, and duplex settings but does not include MAC address information. Option D is incorrect because show cdp neighbors displays information about directly connected Cisco devices including device ID, platform, and capabilities but does not show the MAC address table.
