Module 15: Troubleshooting Windows Network Services: DNS, DHCP, and Connectivity Issues Explained

Troubleshooting Windows Network Services involves diagnosing and resolving issues with core services like DNS, DHCP, IP configuration, and Active Directory that affect network connectivity, name resolution, and user access in a Windows Server environment.

Troubleshooting Network Problems: Identify Symptoms, Causes, and Fixes

Troubleshooting network problems involves identifying symptoms like slow connectivity or lost access, researching the root cause (hardware, DNS, DHCP, firewall, etc.), and applying corrective actions to restore stable network operations.

Researching the Symptoms of Network Problems

Common Symptoms to Watch For:

Symptom	Possible Indicators
🔄 Slow Network Speeds	Lag during file transfers, slow website loading
❌ No Internet Access	Yellow warning sign or “Connected but no internet”
🔌 Intermittent Connectivity	Frequent dropouts or unstable video calls
🔒 Access Denied to Network Resources	Cannot reach file shares, printers, or mapped drives
🌐 Unresolved Hostnames	“Server not found” or DNS resolution errors

Tools to Use:

ping, tracert – for latency & routing
ipconfig, netstat – for IP and port info
Event Viewer – for network-related logs
Network and Sharing Center – for visual connection status

Identifying the Causes of Network Problems

Possible Causes:

Category	Common Causes
✅ Hardware	Faulty cables, failing NIC, switch/router failure
🛠️ Configuration	Wrong IP settings, subnet mismatch, gateway issues
🌐 DNS/DHCP	DNS misconfigurations, DHCP not assigning IPs
🔐 Firewall/Security	Blocked ports, antivirus interference
👥 User Errors	Incorrect passwords, unplugged cables

Resolving Network Problems

Basic Fixes:

Issue	Resolution
❌ IP Conflict or No IP	Release/renew IP: `ipconfig /release` + `/renew`
🌐 DNS Not Resolving	Set static DNS (e.g., 8.8.8.8), flush DNS: `ipconfig /flushdns`
🔌 Intermittent Connection	Replace cable/switch/router, update NIC driver
🔒 Cannot Access Shared Resources	Check permissions, firewall rules, and credentials
🔄 Slow Network	Monitor bandwidth hogs, restart switch/router, use QoS

Identifying the Symptoms and Causes of Network Problems

Identify Error Messages by Using Windows 2019 Help or the net helpmsg Command

Diagnose Network Problems by Using Troubleshooters

Diagnose Network Problems by Using Event Viewer

Resolving TCP/IP Problems

Resolving TCP/IP problems involves identifying and fixing issues in the transmission and configuration of the TCP/IP protocol stack that impact connectivity, routing, and communication in a Windows-based network.

What is TCP/IP?

TCP/IP (Transmission Control Protocol/Internet Protocol) is the foundation of all networking and communication in Windows systems. When there’s a TCP/IP problem, users may experience internet disconnection, slow performance, or unreachable network resources.

Common TCP/IP Problems:

Issue	Example Symptoms
❌ IP Configuration Errors	No internet, APIPA (169.254.x.x) addresses
🌐 DNS Resolution Failures	Cannot reach websites or internal services by name
🔁 Subnet/Gateway Mismatches	Unable to reach devices outside local network
🛑 Duplicate IP Addresses	Random disconnections or “IP conflict” errors
🔌 Network Stack Corruption	Persistent disconnects, no response to ping

1. Restart Network Hardware

Restart the modem/router
Reconnect Ethernet or reset Wi-Fi

2. Check IP Configuration

Open CMD and run:

bash ipconfig /all

Verify:

Correct IP address
Subnet mask
Default gateway
DNS server

3. Release and Renew IP Address

bash ipconfig /release
ipconfig /renew

Use when the system isn’t receiving a proper IP from DHCP.

4. Flush DNS Cache

Fixes name resolution problems:

bash ipconfig /flushdns

5. Reset TCP/IP Stack

Fully resets TCP/IP to default state:

bash netsh int ip reset
netsh winsock reset

Reboot your computer afterward.

6. Ping and Tracert

To test network reachability:

bash ping 8.8.8.8
ping www.google.com
tracert www.google.com

If ping to IP works but not to hostname → DNS issue.

7. Disable IPv6 (if causing issues)

Sometimes, disabling IPv6 helps on older networks:

Go to Network Adapter Settings
Uncheck Internet Protocol Version 6 (TCP/IPv6)

8. Check Windows Firewall or Antivirus

Temporarily disable firewall/AV to test
Ensure network discovery is allowed

9. Check for Driver or NIC Issues

Update or reinstall network adapter drivers
Run: devmgmt.msc → Network Adapters → Update driver

IP-to-MAC Resolution
ARP	Resolves IP addresses to MAC addresses that are used by LAN hardware
ARP Cache	Contains IP address–to–MAC address mappings
Dynamic Entries	Automatically added to and deleted from the ARP cache during TCP/IP sessions with remote computers
Static Entries	Remain in the cache until the computer is restarted

Lab A: Troubleshooting Routing

How to Fix Name Resolution Problems in Windows Networks (DNS Troubleshooting Guide)

Resolving name resolution problems involves diagnosing and fixing issues where domain names fail to resolve into IP addresses, usually due to DNS misconfigurations, cache corruption, or unreachable name servers

Name resolution is the process of translating human-friendly domain names (like google.com) into IP addresses that computers use to communicate. This is typically done using the Domain Name System (DNS).

How to Implement SNMP Service in Windows Server (Step-by-Step Guide)

Implementing the Windows SNMP Service allows network administrators to monitor and manage Windows-based devices using SNMP-enabled monitoring tools like PRTG, SolarWinds, or Nagios. It enables real-time performance tracking and alerting.

What Is SNMP on Windows?

SNMP (Simple Network Management Protocol) is a standard protocol used to collect and organize information about managed devices on IP networks. In Windows, the SNMP service lets the OS act as an SNMP agent, sending system data to a monitoring server.

1. Install SNMP Service (Windows Server 2016/2019/2022)

Using Server Manager:

Open Server Manager
Click Add Roles and Features
Choose Features
Select SNMP Service and SNMP WMI Provider
Complete installation and restart if required

Using PowerShell:

powershell Install-WindowsFeature -Name SNMP-Service -IncludeAllSubFeature -IncludeManagementTools

2. Enable SNMP via Services Console

Open services.msc
Locate SNMP Service
Set Startup type to “Automatic”
Start the service

3. Configure SNMP Settings

Open Services > SNMP Service > Properties
Go to the Security tab:
- Add Accepted Community Names (e.g., public, private)
- Set permissions (READ ONLY or READ WRITE)
- Add Accepted SNMP Hosts (IP of your NMS/monitoring tool)
Go to the Agent tab:
- Enter Contact and Location
- Select applicable services: Physical, Applications, Internet, etc.

4. Allow SNMP Through Windows Firewall

Open Ports:

UDP 161 (SNMP queries)
UDP 162 (SNMP traps)

PowerShell Command:

powershell New-NetFirewallRule -DisplayName "Allow SNMP" -Protocol UDP -LocalPort 161,162 -Action Allow

How to Monitor Network Activity in Windows Server (Tools & Techniques)

Monitoring the network involves using built-in or third-party tools to track network traffic, performance, availability, and security, ensuring smooth operations and early detection of connectivity or bandwidth issues.

What is Network Monitoring?

Network monitoring is the continuous process of observing your network’s performance and availability. It helps detect failures, bottlenecks, unauthorized access, or unusual traffic patterns. For Windows environments, it includes monitoring bandwidth usage, server response times, dropped packets, and SNMP traps.

Why Network Monitoring is Important

Benefit	Purpose
🛡️ Detects network outages early	Minimizes downtime and user impact
📈 Tracks bandwidth and traffic usage	Helps in capacity planning
⚙️ Identifies misconfigured devices	Prevents security risks and service interruptions
🧠 Supports troubleshooting	Speeds up root cause analysis

Steps to Start Monitoring the Network (Windows)

Install SNMP Service (if not already running)
Configure Performance Monitor:
- Add counters: % Processor Time, Bytes Total/sec, etc.
Set up alerts or thresholds using Event Viewer or third-party tools
Configure logging and archiving for long-term analysis
Deploy centralized monitoring tools like PRTG, Nagios, or Zabbix