CCNA Network Services Security Questions

In NTP, an asterisk (*) indicates the selected time source, while a tilde (~) means the server is reachable but not selected. Option A describes the asterisk, not the tilde.

A tilde (~) indicates the server is reachable but not synchronized; a permanently disabled server due to authentication would show a period (.) or not appear at all.

In the context of NTP, a tilde (~) indicates the server is reachable but not selected as the synchronization source. The router acting as an NTP master would be indicated by the 'master' command or stratum level, not by the tilde symbol.

Access mode is correct for a single PC; trunking is not needed for basic connectivity.

AAA is functioning, as evidenced by successful authentication.

The port status is 'Authorized', indicating successful authentication.

Telnet can cross routed networks because it operates at the application layer over TCP/IP.

Telnet supports both local usernames and external authentication via AAA servers like RADIUS or TACACS+.

Telnet connects via a virtual terminal line (VTY) over the network, not solely from the console port.

The access-class must be applied 'in' to restrict incoming SSH sessions; 'out' controls traffic initiated from the router.

The transport input command should be 'ssh' only to disable Telnet.

The 'secret' keyword should be used for secure password storage; 'password' is less secure.

The 'ip host' command creates a static host table entry on the router, bypassing DNS. It does not fix reverse lookup and is not the intended solution for missing DNS records.

The problem is not with R1's DNS client configuration but with missing records on the DNS server. Repeating correct configuration does not resolve the missing records.

Reverse lookup requires a PTR record. Without it, the reverse query for 198.51.100.10 will still fail.

Incorrect because DHCP relay is unrelated to NAT or inbound server reachability; it only forwards DHCP messages across subnets and does not solve NAT issues.

Incorrect because disabling NAT removes all address translation, preventing private IP addresses from reaching the Internet and breaking outbound connectivity for users.

Incorrect because placing the server in the native VLAN affects Layer 2 segmentation but does not provide a public IP address or influence NAT behavior for inbound access.

Disabling a port does not convert it into a trunk; trunking is a separate configuration for carrying multiple VLANs.

Shutting down ports does not replace VLAN segmentation; VLANs provide logical separation, while port shutdown is a physical access control.

Shutting down ports does not force devices to use SSH; SSH is a management protocol unrelated to port state.

Integrity ensures data accuracy and protection from unauthorized modification, not availability. Availability is the principle that ensures data is accessible when needed.

Authorization does not verify identity; that is authentication. Authorization determines what an authenticated user is allowed to do.

Incorrect because shared generic admin accounts reduce traceability and accountability, making it difficult to audit who made changes or accessed the device, which weakens security.

Incorrect because disabling logging removes visibility into management activities, hindering the ability to detect unauthorized access or troubleshoot issues, which is counterproductive to security.

Incorrect because SSID names pertain to wireless network identification and do not provide any protection for router management-plane access or protocols.

The specific factual error is that a helper-address should not be configured on an interface where the router itself is the DHCP server for that subnet.

The specific factual error is that the helper-address on the LAN interface is not needed and would cause issues, and the excluded-address range is actually correct in this option, but the question's misconfiguration is the excluded-address being too broad.

The specific factual error is that the helper-address on the interface facing the remote server is not configured, so DHCP broadcasts from the 10.0.0.0/30 subnet will not be forwarded.

Disabling DHCP snooping is unnecessary because the other VLANs work, and the scenario does not indicate a trust misconfiguration; the real problem is the incorrect helper address on Vlan20.

This option is wrong because different native VLANs do not prevent an EtherChannel from forming; they can still establish a link if other configurations are compatible. The primary issue in this scenario is related to LACP mode mismatches.

This option is incorrect because EtherChannel can use either PAgP or LACP for negotiation, and both protocols can operate independently of each other. The requirement for both sides to use PAgP in desirable mode is not a necessity for EtherChannel to function.

This option is wrong because EtherChannel can be configured on switch ports without needing to convert them to routed ports. Routed ports are not necessary for EtherChannel to function, as it operates at Layer 2.

Syslog is incorrect because it only records system events, error messages, and notifications. It does not provide detailed traffic flow or bandwidth usage information, so it cannot help identify which flows consume the most bandwidth.

DHCP relay is incorrect as its function is to forward DHCP broadcast requests from clients to DHCP servers across different subnets. It does not analyze or report on traffic flows or bandwidth consumption.

PortFast is incorrect because it is a Spanning Tree Protocol feature that allows edge ports to transition quickly to the forwarding state. It has no role in traffic flow analysis or bandwidth monitoring.

NAT pool size is not a limiting factor with PAT overload; a single address can serve thousands of hosts.

The interface is correctly configured for NAT inside.

Applying multiple access lists to the same pool is allowed and does not create a conflict.

This option is incorrect because the principle of least privilege does not imply that administrators should have no configuration access; rather, it means they should only have the access necessary to perform their job functions.

This option is incorrect because least privilege does not eliminate the need for logging and accounting; instead, it complements these practices by ensuring that access is limited while still requiring oversight and tracking of actions taken by users.

This option is incorrect because the principle of least privilege applies to all network environments, not just wireless guest networks. It is a fundamental security concept that should be implemented across all systems and user roles.

Option A describes the shutdown violation mode behavior, where the port immediately goes err-disabled upon detecting a second unauthorized MAC address. Since the command specifies 'violation restrict', the port does not disable but stays up, so this option is incorrect.

Option C is incorrect because port security never forwards traffic from unauthorized MAC addresses. The switch drops such frames to enforce security policies, so forwarding violating traffic is not possible.

Option D is incorrect because listening and learning states refer to Spanning Tree Protocol (STP) port states, not port security violation responses. Port security violation modes do not cause STP state changes.

The 'ip nat inside source list' command must specify the outside interface (the one with the public IP) for translation, not the inside interface.

NAT overload (PAT) requires the 'overload' keyword to enable port address translation. Without it, the router performs dynamic NAT, which is insufficient for sharing a single public IP among many hosts.

The ACL should match only the internal network that requires translation. Using 'permit any' would translate all traffic, including traffic that should not be translated, potentially breaking connectivity or causing security risks.

Candidates may think that the ACL itself, if still configured, continues to filter traffic even when not applied to an interface.

A common misunderstanding is that the access-group line can persist without a valid ACL and cause some default behavior; in fact the entire command is removed.

Some candidates may confuse direction changes with removal and assume the ACL is still filtering traffic in some way, but the symptom clearly indicates no filtering at all.

A default route on the inside host controls outbound traffic, not inbound connections from the internet.

PAT overload is used for many-to-one translation and would not block inbound traffic if static NAT is already configured.

DHCP relay forwards DHCP requests to a remote server and does not affect inbound HTTP/HTTPS access to a web server.

PAT overload is incorrect because it is designed for many internal hosts sharing a single public IP for outbound traffic, not for providing a fixed public IP for inbound server access.

No NAT is incorrect since private IPv4 addresses are not routable on the public Internet; without NAT, the internal server cannot be reached from outside the private network.

DHCP relay is unrelated to NAT or public reachability; it only forwards DHCP requests across subnets and does not provide any public IP mapping for internal servers.

Syslog is not used for IP address assignment; that function is performed by DHCP.

Syslog does not replace SNMP counters for interface statistics; SNMP remains the primary method for collecting such data.

Availability is incorrect because it focuses on ensuring that systems and data are accessible when needed, not on preventing unauthorized data modification.

Accounting is incorrect since it involves logging and tracking user activities and network events but does not guarantee that the data itself has not been altered.

Confidentiality is incorrect because it protects data from unauthorized disclosure but does not ensure that the data has not been changed or tampered with.

Syslog is incorrect because it focuses on logging device events and messages rather than providing traffic flow or volume information necessary for identifying heavy traffic sources.

DHCP is incorrect since it only assigns IP addresses and network settings to hosts and does not offer any insight into traffic patterns or flow data.

PortFast is incorrect because it is a Spanning Tree Protocol feature that accelerates port forwarding state transitions and does not relate to traffic monitoring or analysis.

DHCP snooping and DAI (Dynamic ARP Inspection) do not address the requirement of disabling a port upon receiving BPDUs; they focus on protecting against rogue DHCP servers and ARP spoofing, respectively.

Root Guard and VTP pruning do not address the requirement of quickly enabling access ports and disabling them upon receiving BPDUs. Root Guard is used to prevent a port from becoming a root port, while VTP pruning optimizes VLAN traffic, neither of which directly manage port states based on BPDU reception.

Port security and CDP do not provide the necessary functionality to disable a port when BPDUs are received. Port security can limit the number of MAC addresses but does not specifically address BPDU handling.

TTL is not the main distinguishing value PAT uses because it changes as packets traverse routers and does not uniquely identify individual flows in NAT translations.

DSCP is a QoS marking used to prioritize traffic and does not play a role in NAT or PAT flow differentiation, so it cannot distinguish inside flows sharing one outside IP.

MAC addresses are Layer 2 addresses that are not preserved across routed NAT boundaries, so they cannot be used to distinguish flows in PAT.

NTP authentication protects the integrity of time synchronization between devices but does not provide any mechanism for monitoring or analyzing network traffic flows or bandwidth usage.

DNS forwarding improves domain name resolution efficiency but does not collect or analyze traffic flow information related to bandwidth consumption.

DHCP snooping is a security feature that prevents unauthorized DHCP servers at Layer 2 and does not provide any traffic profiling or bandwidth monitoring capabilities.

Converting all inside hosts to the same private IP would cause addressing conflicts and break basic connectivity, not enable PAT.

Increasing the NAT pool provides more public addresses but does not allow many users to share one public address via port translation.

Static NAT requires a dedicated public IP per host, preventing many-to-one sharing.

DHCP snooping is a security feature that prevents unauthorized DHCP servers by filtering DHCP messages. It does not forward DHCP broadcasts across VLANs, so it cannot enable clients on different VLANs to receive addresses.

Port security restricts the number and identity of MAC addresses on switch ports to enhance security. It does not affect DHCP broadcast forwarding or enable clients to receive addresses from servers on different VLANs.

NAT overload translates multiple private IP addresses to a single public IP address for outbound traffic. It does not address the issue of forwarding DHCP broadcasts between VLANs or enable DHCP clients to obtain addresses from remote servers.

Integrity is incorrect because it focuses on protecting data from unauthorized changes, not on ensuring access or uptime of systems and data.

Accounting is incorrect as it is part of the AAA framework (Authentication, Authorization, Accounting) and not a component of the CIA triad, so it does not relate to system availability.

Confidentiality is incorrect because it deals with preventing unauthorized disclosure of information, not with ensuring that systems and data are accessible when required.

This option is incorrect because static routes are preferred over dynamic routes in OSPF when both are present, regardless of when they were learned. The static route to 10.55.10.0/24 will be used due to its longer prefix match.

This option is incorrect because OSPF routes do not share equal preference with static routes; the static /24 route will be preferred due to its longer prefix length, making it the best match for the specific destination IP.

This option is incorrect because overlapping routes are valid in routing protocols like OSPF, and both routes can coexist in the routing table. The static route to 10.55.10.0/24 is valid and will be preferred due to its longer prefix length.

Designated ports are selected for each LAN segment to forward traffic away from the root bridge, but they do not represent the best path back to the root bridge on a non-root switch. Therefore, this option is incorrect.

Alternate ports serve as backup paths and remain in a blocking state unless the root port fails. They do not identify the best path back to the root bridge, so this option is incorrect.

Disabled ports do not participate in STP forwarding or path selection and are not related to identifying the best path back to the root bridge, making this option incorrect.

Matching only one source subnet can be accomplished with a standard ACL, so this does not strongly indicate a need for an extended ACL.

Placing an ACL near the destination is a characteristic of standard ACLs, not a criterion that selects an extended ACL.

The scenario assumes both standard and extended ACLs are available; standard ACLs do not exist for IPv6, so this requirement does not apply to the IPv4 ACL choice.

Option B is incorrect because strong authentication and centralized logging serve distinct functions; authentication secures access while logging tracks and analyzes events, enhancing security and compliance.

This option is incorrect because centralized logging does not eliminate the need for authentication; both are essential for a comprehensive security posture. Authentication verifies user identity, while logging tracks access and actions for auditing and incident response.

This option is wrong because strong authentication does not eliminate the need for device event records; both are essential for comprehensive security management. Device event records provide critical insights into system activity, which strong authentication alone cannot address.

The forwarder is unreachable, so keeping it will cause forward lookups to fail. Also, reverse lookup requires a PTR record, which is missing.

Forward lookups require an A record mapping the hostname to an IP address; without it, forward queries return NXDOMAIN.

The scenario expects R1 to be a local DNS server for internal hosts; using an external forwarder for internal hostnames is not best practice and may not resolve internal names if the forwarder doesn't have the records.

DHCP provides IP configuration parameters like default gateway and DNS server, not routing protocol parameters. OSPF area number is a routing protocol setting configured manually on routers, not assigned via DHCP.

DHCP provides IP configuration parameters like default gateway and DNS server, not physical layer settings like switch port duplex. Duplex is configured locally on the switch interface, not assigned via DHCP.

STP root bridge priority is a Spanning Tree Protocol parameter used to elect the root bridge in a switched network, not a DHCP-provided parameter. DHCP can only supply IP configuration parameters like default gateway and DNS server.

Option B is incorrect because it denies all IP traffic from the specified source to the destination, which is broader than required and does not specifically target HTTP traffic on port 80.

Option C is incorrect because it permits HTTP traffic from the specified source to the web server, which is contrary to the requirement to block this traffic. The question specifically asks for a rule that denies HTTP access.

Option D is incorrect because it specifies 'deny udp', which does not block HTTP traffic, as HTTP uses TCP, not UDP. Therefore, it fails to meet the requirement of blocking HTTP from the specified source to the web server.

Standard ACLs are not limited to wireless networks; they can be applied to any interface on a router, including wired connections. This option misrepresents the applicability of standard ACLs.

This option is incorrect because Telnet and SSH use different destination ports; Telnet typically uses port 23, while SSH uses port 22, allowing for distinct filtering in ACLs.

This option is incorrect because SSH can indeed be filtered using ACLs, as they can match traffic based on IP addresses and protocols. Standard ACLs can be applied to control SSH traffic just like any other traffic type.

Static NAT for every host is incorrect because it requires a unique public IP address per internal host, which is inefficient and unnecessary when only outbound access is needed without inbound server publishing.

No NAT is incorrect because private IPv4 addresses are not routable on the public Internet and must be translated to public addresses to communicate externally.

DHCP relay is incorrect because it only forwards DHCP messages between clients and servers and does not perform any IP address translation or NAT functions.

Syslog and NTP are independent protocols; Syslog does not need to run before NTP can synchronize.

NTP works over any IP network; there is no requirement for a trunk port on the management VLAN.

DNS is only needed if the NTP server is referenced by hostname rather than IP address; many configurations use IP addresses directly.

Incorrect because user ports should be configured as access ports, not trunks. Configuring user ports as trunks is unnecessary and can cause security and connectivity issues.

Incorrect because the SVI for VLAN 30 must be active for inter-VLAN routing to function. Shutting down the SVI would prevent routing, not enable it.

Incorrect because changing the trunk native VLAN to VLAN 30 is unrelated to the problem. Native VLAN mismatches affect untagged traffic but do not block VLAN 30 tagged frames if the VLAN is allowed.

Telnet is incorrect because it transmits data in clear text, exposing sensitive information to attackers and failing to protect session contents during transit.

Open wireless access is unrelated to secure remote management; it does not provide encryption or protect administrative sessions, making it irrelevant to the question.

Native VLAN 1 configuration does not affect encryption or security of remote management protocols, so it does not support the goal of protecting session contents.

The access list correctly matches the internal subnet, so this is not the root cause.

Even without overload, dynamic NAT should work for the first 11 hosts; the problem is that return packets are not being translated.

The pool size is not the issue; the router is not translating return traffic due to missing 'ip nat outside'.

Option A is incorrect because multifactor authentication strengthens authentication processes but does not remove the need for authorization policies. Authorization controls determine what an authenticated user can access, which remains essential regardless of the authentication method.

Option C is incorrect because while MFA reduces the risk of phishing attacks by requiring multiple factors, it does not guarantee that credentials can never be phished. Attackers may still find ways to bypass or trick users into revealing multiple factors.

Option D is incorrect because authentication methods like MFA do not replace encryption on the network. Encryption protects data confidentiality and integrity during transmission, which is a separate security function from verifying user identity.

Administrative distance is a routing protocol metric used to select the best path and does not relate to access-switch port security. It does not control port access or prevent unauthorized devices, so option C is incorrect.

Route summarization is a routing optimization technique that reduces routing table size and update traffic. It does not provide any security controls for user-facing switch ports, so option D is incorrect.

Adding another SSID is incorrect because it only creates a new wireless network segment and does not provide any traffic flow or bandwidth usage information. It does not help identify which applications or hosts are using the link.

PortFast is an STP feature that speeds up port transitions on edge ports but does not monitor or analyze traffic flows. It has no relevance to identifying bandwidth usage or application-level visibility.

Using a larger wildcard mask in ACLs affects traffic filtering rules but does not provide analytics or visibility into traffic flows. ACLs do not report on bandwidth consumption or application usage.

Incorrect. DHCP does not resolve hostnames to IP addresses; this is the responsibility of DNS, a separate IP service.

Incorrect. DHCP does not participate in routing protocol operations like OSPF designated router election, which is a function of OSPF itself.

Incorrect. DHCP supplies subnet masks to clients but does not replace the need for subnet masks; subnetting remains a fundamental network design concept.

Placing an extended ACL as close to the destination can lead to unnecessary traffic being processed by intermediate devices, which is inefficient. Extended ACLs are designed to filter traffic based on source and destination, so positioning them closer to the source enhances performance and security.

This option is incorrect because placing an extended ACL only on the default gateway limits its effectiveness in controlling traffic originating from various sources across the network. Extended ACLs should be strategically placed closer to the source to filter traffic before it reaches the destination.

Placing an extended ACL only on WAN interfaces can lead to inefficient traffic filtering, as it may not adequately control traffic originating from internal sources. Extended ACLs should ideally be positioned close to the source to effectively manage traffic before it reaches the destination.

Incorrect. The `inside` keyword only marks an interface as internal for NAT direction but does not enable multiple hosts to share one outside address.

Incorrect. The access list (`list 1`) specifies which internal addresses are translated but does not activate PAT or many-to-one sharing by itself.

Incorrect. Specifying the interface determines the outside IP address used for translation but does not enable PAT without the `overload` keyword.

Incorrect. DHCP pools assign IP addresses to clients and are unrelated to NAT or PAT configuration. Lack of a DHCP pool on the outside interface does not affect PAT functionality.

Incorrect. CDP is a Layer 2 protocol used for device discovery and does not influence NAT or PAT operations. Its absence does not cause internet access issues related to PAT.

Incorrect. Syslog servers are used for logging and monitoring router events. Not configuring a syslog server does not impact NAT translation or internet connectivity.

Static NAT only provides a one-to-one mapping between private and public IP addresses, so it cannot support multiple internal users sharing one public IP address simultaneously, making it unsuitable for the scenario.

No NAT is incorrect because private IPv4 addresses are not routable on the public Internet; without NAT, internal users cannot access external resources using private IPs alone.

DHCP relay is unrelated to NAT or IP address translation; it simply forwards DHCP requests between clients and servers and does not enable sharing of public IP addresses for Internet access.

Telnet transmits credentials in plaintext, making it less secure than SSH and opposite to the goal of stronger authentication.

An ACL restricts source addresses but does not strengthen the authentication factor itself; it is an authorization control, not an authentication improvement.

Removing password authentication and relying on location removes all credential verification, making the device vulnerable to unauthorized access from permitted locations.

The specific factual error is that the ACL must be named 'FILTER_HTTP', but this option uses a numbered ACL (100).

The specific factual error is that the ACL does not include an explicit deny ip any any, which is needed to satisfy the requirement of denying all other IP traffic.

The specific factual error is that the ACL is applied to the wrong interface (GigabitEthernet0/1 instead of GigabitEthernet0/0).

This option is incorrect because Telnet uses TCP as its transport protocol, not UDP. Therefore, denying TCP traffic is relevant for blocking Telnet, and the statement about UDP is factually wrong.

This option is incorrect because standard ACLs filter only by source IP address and cannot filter by protocol or port. The question requires filtering by service (Telnet), which necessitates an extended ACL, making this option invalid.

This option is incorrect because the 'host' keyword is valid in extended ACLs and is commonly used to specify a single IP address for precise matching. There is no restriction against using 'host' with TCP statements.

The option 'logging trap debugging' sets the trap level to 7, which includes all syslog messages from debugging (least severe) up to emergencies (most severe). This floods the syslog server with excessive data, beyond just warnings and critical events, making it unsuitable for the requirement.

The option 'logging trap notifications' sets the trap level to 5, which includes notifications and all more severe messages. However, notifications are less severe than warnings, so this setting would include informational messages that are not requested, making it incorrect.

The option 'logging trap informational' sets the trap level to 6, which includes informational messages and all more severe messages. This level is less severe than warnings and includes many more messages than requested, so it does not meet the requirement.

Incorrect because source restriction does not replace the need for secure transport protocols like SSH; encryption and authentication remain essential for secure management.

Incorrect because logging is still necessary to maintain visibility and audit trails of administrative access attempts, even when source restriction is applied.

Incorrect because source restriction is not limited to wireless management; it applies broadly to all administrative access methods on Cisco devices.

Logging trap level controls which severity messages are forwarded, not the accuracy of the timestamps.

SNMP v3 misconfiguration impacts SNMP traps, not syslog messages, which are sent independently via a different transport.

Cache timeout affects flow export frequency, not the accuracy of the timestamps inside the flow data.

Option B is incorrect because DHCP, not DNS, is responsible for automatically assigning IP addresses to devices on a network. DNS only resolves names to IP addresses after assignment.

Option C is incorrect because DNS does not replace default gateways. Default gateways are necessary for routing traffic outside the local subnet, a function unrelated to DNS name resolution.

Option D is incorrect because DNS has no role in Spanning Tree Protocol (STP) operations, including root bridge election, which is a Layer 2 loop prevention mechanism.