Network Troubleshooting

A network administrator is troubleshooting remote administration access to an edge router ($172.28.10.1$). Systems engineers on the management network ($10.40.8.0/24$) report that ping requests to the router succeed, but SSH connections to port 22 time out. Upon inspecting the router interface's inbound Access Control List (ACL), the administrator reviews the following entries:

access-list 105 permit icmp 10.40.8.0 0.0.0.255 any
access-list 105 permit udp 10.40.8.0 0.0.0.255 host 172.28.10.1 eq 22
access-list 105 deny ip any any

Which of the following is the root cause preventing SSH access to the router?

A network engineer is responding to a critical datastore access failure across a virtualized server cluster immediately following scheduled network switch maintenance. Place the following troubleshooting steps in the correct chronological sequence according to the official CompTIA troubleshooting methodology.

A network engineer is troubleshooting several Layer 2 connectivity issues across enterprise switch stacks. Match each observed diagnostic log output or interface symptom on the left with its correct underlying root cause on the right.

A network engineer is troubleshooting an issue where workstations on a branch office subnet ($192.168.30.0/24$) cannot access an internal corporate web server ($10.50.4.100$) over HTTPS or reach external websites. Local inter-VLAN traffic works normally.

The engineer inspects the workstation configuration and branch router logs:

Workstation Network Settings:
- IP Address: $192.168.30.45$
- Subnet Mask: $255.255.255.0$
- Default Gateway: $192.168.30.1$

Branch Router Routing Table (`show ip route` excerpt):
- $C\quad 192.168.30.0/24$ is directly connected, `GigabitEthernet0/0.30`
- $S*\quad 0.0.0.0/0$ [1/0] via $203.0.113.254$

Branch Router Outbound ACL (`show ip access-lists OUTBOUND_FILTER` excerpt):
- `10 permit udp 192.168.30.0 0.0.0.255 host 10.50.4.100 eq 443`
- `20 deny ip 192.168.30.0 0.0.0.255 10.50.0.0 0.0.255.255`

Which TWO factors are directly responsible for the observed connectivity failure? (Select TWO.)

A network administrator is troubleshooting an issue where new Linux servers in VLAN 105 ($192.168.105.0/24$) fail to acquire dynamic IP addresses from a central DHCP server ($10.10.1.50$) located across a Layer 3 boundary. The router subinterface for VLAN 105 (`Gi0/0.105`) is configured with `ip helper-address 10.10.1.50`. However, packet captures show that client DHCP DISCOVER requests sent to $255.255.255.255$ are received on `Gi0/0.105`, but no unicast DHCP messages are ever transmitted from the router toward $10.10.1.50$, and client systems eventually assign themselves APIPA addresses. Upon reviewing the router interface configuration and DHCP server status, which TWO conditions would explain this behavior?

A network systems engineer is investigating severe network degradation on a newly deployed 90-meter Category 6A UTP link connecting an access switch to a server cluster. Server nodes on this link report intermittent link flapping, high frame loss, and an inability to obtain dynamic IP configurations from the centralized DHCP server. To conduct a comprehensive diagnosis of both physical layer integrity and transport protocol operations for this issue, which TWO of the following tools or capture filter configurations should the engineer utilize? (Select TWO)

A network administrator is troubleshooting connectivity issues for a workstation that cannot access a secure web portal ($10.50.20.15:443$). The workstation is assigned an IP address of $192.168.5.85/24$ with a default gateway configured as $192.168.6.1$. A ping test from the workstation to its configured default gateway fails. Furthermore, inspection of the interface ACL on the intermediate router shows only the following rule: `permit tcp 192.168.5.0 0.0.0.255 host 10.50.20.15 eq 80`. Which TWO of the following configurations are causing the connection to fail? (Select TWO)

Match each physical layer network issue or diagnostic requirement with the most appropriate hardware testing tool.

A network engineer is troubleshooting high frame error rates and link degradation on a 90-meter Category 6 twisted-pair cable drop connecting a core switch to a desktop client. A basic continuity wiremap tester indicates that all eight pins are correctly wired straight-through (1-to-1 through 8-to-8) with no open or short circuits. However, when the link autonegotiates to 1000BASE-T, the connection experiences severe Near-End Crosstalk (NEXT) and high packet loss. Which diagnostic tool should the engineer utilize to identify the physical cable fault causing this issue?

A network technician is troubleshooting severe latency and high frame retransmission rates on a 2.4 GHz wireless network within an office suite. Signal spectrum analysis reveals that three neighboring access points are broadcasting on channels 1, 2, and 3, resulting in significant adjacent-channel interference. Which of the following actions should the technician take to remediate these wireless signal issues? (Select TWO.)

A network engineer is troubleshooting a newly connected point-of-sale terminal on VLAN 45 ($10.45.10.0/24$) that cannot communicate with the accounting database. Executing `ip addr show eth0` on the terminal produces the following output:

text
eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default
inet 169.254.112.85/16 brd 169.254.255.255 scope global eth0
valid_lft forever preferred_lft forever

Inspection of the default gateway router configuration for VLAN 45 displays the following settings:

text
interface GigabitEthernet0/0.45
encapsulation dot1Q 45
ip address 10.45.10.1 255.255.255.0
ip helper-address 10.100.20.14

A recent IP audit confirms that the active central enterprise DHCP server resides at address $10.100.20.15$. What is the primary root cause of the terminal failing to acquire a valid network IP address?

A network technician receives reports that internal workstations are intermittently directed to an external IP address when resolving the internal hostname `app.corp.local`. To investigate, the technician executes `nslookup app.corp.local 10.0.4.10` from a CLI interface and receives the following output:

Server: internal-dns.corp.local
Address: 10.0.4.10

Non-authoritative answer:
Name: app.corp.local
Address: 203.0.113.88

Based on this output, which of the following is the most accurate analysis of the issue?

A network administrator is using a packet analyzer to troubleshoot an issue where client hosts on a remote subnet cannot obtain IP addresses automatically. The administrator suspects that DHCP relay messages are not reaching the centralized DHCP server. To verify if relayed bootstrap requests are arriving at the server's network interface card, which protocol and port criteria should the administrator filter for in the packet analyzer capture?

A network administrator on a Linux workstation is troubleshooting an inability to reach a remote HTTPS service hosted at 10.20.30.50 on custom port 8443. Following a structured bottom-up OSI troubleshooting methodology, in what sequence should the administrator execute the following command-line diagnostics to systematically isolate the failure?

A network administrator is troubleshooting an issue where containerized API gateways fail to communicate with an internal microservice cluster across a virtual overlay network. The administrator established a theory that an overly restrictive container firewall policy was blocking traffic and verified this theory by temporarily allowing all traffic, which immediately restored connectivity. Which of the following actions should the administrator take in the immediate next phases of the CompTIA troubleshooting methodology? (Select TWO.)

A network administrator is isolating connectivity failures on a newly commissioned twisted-pair workstation drop. The administrator needs to verify the physical layer integrity to pinpoint cable distance faults and analyze captured broadcast traffic to identify rogue DHCP server offers on the subnet. Which TWO tools or capabilities should the administrator utilize to achieve these objectives? (Select TWO)

A network administrator is troubleshooting a DNS lookup issue on a Linux client. Standard hostname resolution over UDP functions normally for small queries, but operations requiring larger payloads fail. When testing the DNS server at IP address `172.16.10.5` using the TCP mode (`+vc` flag), the administrator observes the following output:

text
$ dig @172.16.10.5 app.corp.internal +vc
;; Connection to 172.16.10.5#53(172.16.10.5) for app.corp.internal failed: connection refused.

Which of the following is the most likely root cause of this failure?

Match each observed wireless network performance symptom to its corresponding Radio Frequency (RF) root cause or signal behavior.

A network administrator is troubleshooting an issue where a Windows client workstation fails to resolve internal hostnames. To isolate where name resolution fails within the OS lookup hierarchy, in what order does a standard Windows client attempt to resolve a target hostname? Arrange the following resolution mechanisms from first evaluated (top) to last evaluated (bottom).

A network technician is troubleshooting a newly connected client workstation that cannot access local network resources or the internet. Executing `ipconfig /all` on the workstation yields the following output:

Ethernet adapter Ethernet0:
Connection-specific DNS Suffix . :
Link-local IPv6 Address . . . . . : fe80::d4a2:810f:3c21:7a9a%12
IPv4 Address. . . . . . . . . . . : 169.254.108.42
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :

Which of the following is the most likely cause of this workstation's IP configuration?