Network Troubleshooting

A network engineer is troubleshooting reachability issues for a newly provisioned monitoring server located in an enterprise branch office. The server is assigned the static IP address $10.64.36.195$ with a subnet mask of $255.255.255.192$ ($/26$). The default gateway configured on the server interface is $10.64.36.129$. The server can successfully ping its own IP address, but all attempts to reach the default gateway or remote networks fail with a destination host unreachable error. Which of the following identifies the root cause of this connectivity failure?

A systems engineer is troubleshooting an issue where corporate users cannot authenticate to an enterprise wireless network. The engineer established a theory that an expired SSL/TLS certificate on the RADIUS server was causing EAP-TLS handshake failures and confirmed this theory by analyzing RADIUS authentication failure logs. Which of the following actions should the engineer perform NEXT in accordance with the CompTIA troubleshooting methodology? (Select TWO.)

Match each wireless network troubleshooting scenario or signal anomaly to its primary underlying cause.

A network technician suspects that a workstation's local DNS resolver is returning cached, out-of-date IP addresses for an internal server. The technician needs to test name resolution by sending a DNS query directly to a specific authoritative name server rather than relying on the local resolver configuration. Which command-line utility should the technician use to perform this direct query?

A network engineer is troubleshooting why internal workstations cannot access a newly deployed secure internal portal at `vault.corp.local`. The engineer executes `dig vault.corp.local` on a client workstation and captures the following terminal output:

;; QUESTION SECTION:
;vault.corp.local. IN A

;; ANSWER SECTION:
vault.corp.local. 300 IN CNAME sec-srv01.corp.local.

;; ADDITIONAL SECTION:
sec-srv01.corp.local. 300 IN A 10.200.5.25

Next, the engineer remotely accesses the destination server (`10.200.5.25`) and runs `netstat -tuln`, which displays:

Proto Recv-Q Send-Q Local Address Foreign Address State
tcp 0 0 10.200.5.25:8443 0.0.0.0:* LISTEN
udp 0 0 0.0.0.0:53 0.0.0.0:* LISTEN

When end users attempt to navigate to `https://vault.corp.local` using standard browser defaults, the request immediately fails with a "Connection Refused" error. Based on the command outputs provided, which root cause explains why clients are unable to connect?

An infrastructure engineer is analyzing network logs to determine why an application server located at $10.50.20.15$ cannot transmit syslog data to a remote log collector at $172.18.4.50$. The collector receives log streams using UDP port $514$. The engineer inspects the active router interface access control list (ACL):

text
Extended IP access list ENTERPRISE_OUT
10 permit tcp 10.50.20.0 0.0.0.63 host 172.18.4.50 eq 514
20 permit ip 10.50.20.0 0.0.0.63 10.50.0.0 0.0.255.255
30 deny ip any any

Which of the following identifies the root cause of this connectivity failure?

A network engineer is investigating an inter-switch trunk link issue between Switch-A and Switch-B. Console logs on Switch-A continuously report "%CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet0/1 (50), with Switch-B GigabitEthernet0/1 (10)". Furthermore, hosts assigned to VLAN 50 on Switch-A are unable to reach services on VLAN 50 connected to Switch-B, and frame traffic is leaking into VLAN 10. Which TWO configuration actions must be performed to restore proper Layer 2 trunking and isolation? (Select TWO.)

A network administrator is troubleshooting an issue where a client workstation is resolving an outdated IP address for a local server. Arrange the standard operating system name resolution steps in order from FIRST evaluated source to LAST evaluated source during a hostname lookup request.

During a network audit, a technician discovers that Switch-1 has its trunk interface native VLAN set to VLAN 10, while Switch-2 on the opposite end of the trunk link has its native VLAN set to VLAN 20. Which of the following issues will occur as a direct result of this misconfiguration?

A network administrator installs a new single-mode fiber-optic cable run between two network switches in adjacent buildings. Which tool should the administrator use to measure signal attenuation and pinpoint light loss along the fiber link?

A network technician is troubleshooting an intermittent Gigabit Ethernet connection over a 70-meter Category 6 UTP cabling run between a core switch and a high-density wireless access point. Although a basic continuity wiremapper shows all eight conductors properly connected pin-to-pin, the link frequently drops or negotiates down to 100 Mbps under high traffic loads. Which of the following diagnostic steps or corrective actions should the technician take to identify and resolve this issue? (Select TWO.)

A network technician needs to verify basic ICMP IP reachability and trace the hop-by-hop route from a Windows workstation to a remote server at 10.0.4.15. Which of the following command-line utilities should the technician use? (Select TWO.)

A network engineer is troubleshooting high optical attenuation along a 1,500-meter single-mode fiber-optic link between two data center facilities. While an optical power meter confirms that overall signal strength drops below acceptable thresholds, it cannot identify where along the cable run the issue exists. Which hardware tool should the engineer use to pinpoint the exact distance to the microbend or splice failure causing the signal loss?

A user connects a laptop to a wired network jack in a remote conference room but cannot access any internal or external network resources. A technician executes `ipconfig /all` on the workstation and receives the following output:

IPv4 Address. . . . . . . . . . . : 169.254.22.81
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :

Which of the following is the most likely cause of this issue?

A network technician is troubleshooting connectivity failures on a newly provisioned branch office subnet, VLAN 70 ($10.70.0.0/23$). Client workstations connected to VLAN 70 fail to access corporate resources and receive autoconfigured IP addresses in the range $169.254.18.1$ to $169.254.18.254$ with a subnet mask of $255.255.0.0$. The centralized DHCP server resides on VLAN 10 ($10.10.0.50$). Inspection of the Layer 3 switch reveals that Interface VLAN 70 is configured with IP address $10.70.0.1/23$, but no IP helper address is configured, and logging on the DHCP server indicates that the IP pool for $10.70.0.0/23$ has reached $100\%$ capacity.

Which of the following factors explain why client devices are assigned $169.254.x.x$ addresses and detail the required remediation steps? (Select TWO.)

Match each network troubleshooting task to the most appropriate hardware tester or protocol analysis tool.

A network technician is investigating a situation where users at a remote branch office cannot reach external websites following a WAN router update. The technician gathered information and established a theory that an access control list (ACL) on the edge router was inadvertently blocking outbound DNS traffic on UDP port 53. The technician then applied a temporary test rule and performed a lookup, confirming that the ACL was indeed the root cause of the failure. According to the CompTIA troubleshooting methodology, which of the following actions should the technician perform NEXT?

A network administrator is troubleshooting an intermittent reachability issue affecting a Linux web server located in a corporate DMZ subnet ($10.50.100.0/24$). Internal workstations on the LAN ($192.168.10.0/24$) can ping their local default gateway ($192.168.10.1$), but cannot reach the web server at $10.50.100.45$ on TCP port 443. The administrator executes diagnostic commands and observes the following output:

text C:\Users\admin> traceroute 10.50.100.45 traceroute to 10.50.100.45, 30 hops max, 60 byte packets 1 192.168.10.1 (192.168.10.1) 1.102 ms 0.985 ms 0.950 ms 2 10.200.1.1 (10.200.1.1) 3.421 ms 3.211 ms 3.105 ms 3 * * * 4 * * *

A inspect of the gateway router ($10.200.1.1$) inbound Access Control List (ACL) on the interface facing the core router reveals:

text 10 permit tcp 192.168.10.0 0.0.0.255 10.50.100.0 0.0.0.255 eq 80 20 permit icmp 192.168.10.0 0.0.0.255 10.50.100.0 0.0.0.255 30 deny ip any any

Additionally, direct diagnostic checks on the web server ($10.50.100.45$) show its IPv4 address is configured as $10.50.100.45/24$ with a default gateway configured as $10.50.101.1$.

Which TWO of the following underlying issues are preventing workstation connections to the web server over HTTPS?

Users in an office building report frequent dropouts and poor throughput on the 2.4 GHz wireless network. A network administrator conducts a frequency audit and discovers that neighboring access points are assigned to non-overlapping channels 1, 6, and 11. However, the internal access point experiencing issues is configured to use Channel 3 with a 40 MHz channel bonding width. Which of the following identifies the primary root cause of the wireless performance degradation?

A network technician installs new Category 6 UTP cable runs in a renovated office space. After terminating the cables, the technician uses a basic pin-to-pin continuity tester, which confirms that all eight conductors are correctly wired 1-to-1 at both ends. However, when workstations are connected, network performance is severely degraded by high rates of Near-End Crosstalk (NEXT) and frame errors. Which diagnostic tool should the technician use to identify the split-pair anomaly causing this signal degradation?