Network Troubleshooting

A network engineer is troubleshooting wireless performance issues in a multi-story office building. Wireless site survey logs indicate that client devices in crowded conference rooms remain stickily connected to distant access points (APs) with a weak RSSI of -83 dBm, causing slow throughput and dropped VoIP calls. Simultaneously, the 2.4 GHz spectrum is severely saturated with high client density. Which of the following actions should the engineer take to resolve these wireless connectivity and coverage issues? (Select TWO.)

A network administrator is investigating an issue where a workstation configured with IPv4 address $192.168.20.45/24$ cannot connect to an internal HTTPS server at $10.50.10.100:443$. The network path spans multiple VLANs across a Layer 3 switch, a core router, and perimeter firewalls. Following a systematic network troubleshooting methodology, place the diagnostic steps in the correct logical sequence to systematically isolate whether the root cause lies within the host setup, default gateway reachability, routing table entries, or ACL filtering.

During a routine wireless performance audit of a corporate facility, an administrator observes severe packet loss and elevated frame retransmissions among clients connected to 2.4 GHz access points. Signal strength measurements indicate strong coverage (-55 dBm) across all work areas. Inspection of the wireless controller configuration reveals that adjacent access points are operating on channels 1, 2, 4, and 5. Which of the following represents the primary root cause of this connectivity issue?

A network administrator runs the following query on a client workstation to test hostname resolution:

> nslookup webserver.corp.local
Server: dns1.corp.local
Address: 10.0.0.10

*** dns1.corp.local can't find webserver.corp.local: Non-existent domain

The administrator verifies that the target server is powered on, fully functional, and reachable directly by its IP address. Which of the following is the most likely cause of this issue?

A network technician executes `ipconfig` on a workstation that is unable to reach local network resources. The output displays an IPv4 address of $169.254.12.89$ and a subnet mask of $255.255.0.0$. Which of the following is the most likely cause of this issue?

A network technician is systematically troubleshooting a Linux workstation that fails to resolve an internal fully qualified domain name (FQDN). Arrange the following diagnostic steps in the correct order, starting from local client configuration inspection and escalating through to upstream network infrastructure isolation.

A network administrator is troubleshooting an intermittent physical layer failure on a newly provisioned 90-meter Category 6A unshielded twisted-pair (UTP) link connecting a core switch to a server farm switch. A standard continuity test verifies 1-to-1 pin mapping with no opens or shorts. However, when the link auto-negotiates to 10GBASE-T, the switch interfaces report extremely high cyclic redundancy check (CRC) error counts and dropped frames, whereas forcing the link speed down to 1000BASE-T yields stable performance. Which diagnostic tool should the administrator use to pinpoint the exact location and nature of this signal degradation along the cable run?

Employees in a newly renovated office suite report that laptops connected to the 5 GHz Wi-Fi network experience severe signal drop-offs and low throughput when moving inside glass-walled conference rooms. However, clients connected to the 2.4 GHz wireless network maintain stable signal strength throughout the entire floor. Diagnostic site survey tools reveal a significant drop in RSSI specifically when receiving 5 GHz signals behind the newly installed tinted glass walls. Which of the following is the primary cause of the performance degradation on the 5 GHz band?

A network administrator applies the following extended Access Control List (ACL) to the inbound direction of interface GigabitEthernet0/1 on a branch router to allow subnet `192.168.50.0/24` access to a web server at `10.10.20.100`:

text
Router# show access-lists 105
Extended IP access list 105
10 permit tcp 192.168.50.0 0.0.0.255 host 10.10.20.100 eq 443
20 permit tcp 192.168.50.0 0.0.0.255 host 10.10.20.100 eq 80

Immediately after applying this ACL, workstations on the `192.168.50.0/24` subnet report that they can no longer reach external internet sites or perform domain name resolution via the internal DNS server at `10.10.10.5`. Which of the following best explains the root cause of this connectivity failure?

A network administrator deployed a new internal database server named `db-primary` with IP address $172.16.45.10$ inside the `internal.corp.net` DNS zone. Users situated on workstations within the `sales.corp.net` domain report that querying short hostname `db-primary` fails, whereas querying the fully qualified domain name (FQDN) succeeds.

The administrator executes the following troubleshooting commands from a user workstation in `sales.corp.net`:

C:\> nslookup db-primary
Server: dc1.sales.corp.net
Address: 172.16.10.5

*** dc1.sales.corp.net can't find db-primary: Non-existent domain

C:\> nslookup db-primary.internal.corp.net
Server: dc1.sales.corp.net
Address: 172.16.10.5

Name: db-primary.internal.corp.net
Address: 172.16.45.10

Which of the following configuration changes will resolve the short hostname resolution failure for all workstations in `sales.corp.net`?

A user reports that a recently updated internal web application still directs their browser to an obsolete IP address on their local client machine. In what order should a network technician perform the following steps to systematically troubleshoot and resolve this stale name resolution issue?

A network administrator receives reports that newly arriving wireless clients on a high-density office VLAN ($192.168.32.0/23$) are unable to access network resources. Inspecting an affected workstation via `ipconfig /all` reveals the following output:

text
IPv4 Address. . . . . . . . . . . : 169.254.112.45
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :
DHCP Server . . . . . . . . . . . :

Wireless 802.1X authentication logs show that clients authenticate successfully, but DHCP lease requests time out. Further inspection of the centralized DHCP server shows that the scope for $192.168.32.0/23$ has $508$ active leases out of $508$ total allocated addresses, with a default lease duration of $8$ days.

Which of the following actions is the most appropriate resolution to fix the IP address assignment failure?

A network administrator is investigating an issue where corporate users cannot authenticate to the 802.1X wireless network following a server maintenance window. The administrator suspects that an expired RADIUS server SSL certificate is preventing successful EAP-TLS handshakes. To test this theory, the administrator installs a valid test certificate on a staging RADIUS server and successfully authenticates a test client. According to the CompTIA troubleshooting methodology, what is the immediate NEXT step the administrator should perform?

A network administrator has verified that a recently modified firewall access control list (ACL) blocking TCP port 636 is the root cause of directory authentication failures for hybrid cloud VPN users. The administrator confirmed this theory after testing the ACL modification in a staging environment. According to the CompTIA troubleshooting methodology, which TWO of the following actions should the administrator perform NEXT during the upcoming phase? (Select TWO.)

A network administrator is troubleshooting an intermittent 10GBASE-LR single-mode optical fiber link between two campus buildings. Switch port diagnostics indicate high optical signal attenuation and excessive return loss (back reflection) following a recent patch panel maintenance window. Optical transceivers on both endpoints report normal transmit power levels. Which of the following actions should the network administrator perform to accurately pinpoint the fault location and resolve the physical layer degradation? (Select TWO.)

A user's workstation is assigned the static IP address $10.0.4.50$ with a subnet mask of $255.255.255.0$. The workstation can successfully ping other local computers on the $10.0.4.0/24$ network, but it cannot reach any servers on external subnets or the internet. An administrator reviews the network configuration and notes that the default gateway is set to $10.0.5.1$. Which of the following is the root cause of the outbound connectivity issue?

A network administrator is troubleshooting connectivity issues on a corporate wireless guest network spanning the $192.168.100.0/24$ subnet. Transient users report that their laptops periodically fail to connect to network resources and receive self-assigned IP addresses in the $169.254.0.0/16$ range during peak operating hours. Upon inspecting the central DHCP server status, the administrator observes the following command output snippet:

text
DHCP Scope: Guest_VLAN100
Subnet Prefix: 192.168.100.0/24
Range: 192.168.100.10 - 192.168.100.250
Total Scope Addresses: 241
Active Leases: 241 (100% utilized)
Pending Requests: 14 (Dropped - No available addresses)
Lease Duration: 8 days 00:00:00

Physical attendance logs confirm that no more than 60 guest users are ever present in the facility concurrently. Which of the following is the most likely root cause of this issue?

A network engineer is troubleshooting a client workstation that cannot connect to an internal web portal using its hostname `srv01.corp.internal`. The engineer executes two `nslookup` queries from the client's command prompt:

text
C:\> nslookup srv01.corp.internal
Server: UnKnown
Address: 192.168.1.1
*** UnKnown can't find srv01.corp.internal: Non-existent domain

C:\> nslookup srv01.corp.internal 10.0.0.53
Server: dc01.corp.internal
Address: 10.0.0.53

Name: srv01.corp.internal
Address: 10.0.0.150

Based on the output above, which of the following are the MOST likely root causes of the name resolution issue on the workstation? (Select TWO.)

Match each physical layer cabling diagnostic tool to the primary troubleshooting task or measurement it is designed to perform.

An IT technician is troubleshooting name resolution issues on an administrator workstation. The technician issues an `nslookup` command for `app.finance.local` and receives a successful reply pointing to `192.168.10.50`. However, when attempting to ping `app.finance.local` from the same machine, the system attempts to send traffic to `10.0.0.99` and times out.

text
C:\Users\Admin> nslookup app.finance.local
Server: dns01.corp.internal
Address: 10.0.0.1

Name: app.finance.local
Address: 192.168.10.50

C:\Users\Admin> ping app.finance.local
Pinging app.finance.local [10.0.0.99] with 32 bytes of data:
Request timed out.

Which of the following is the most likely cause of the discrepancy in resolved IP addresses?