Advanced Workstation Connectivity Troubleshooting Guide

Created by Piotr Jamny, Modified on Tue, 2 Dec at 9:46 AM by Piotr Jamny

This guide provides a structured approach for diagnosing situations where a workstation can reach a server partially or not at all. It applies to file sharing, SQL connectivity, RDP, application servers, and general network communication.

1. Basic Network Connectivity

1.1 Test Physical and Local Network Presence

Confirm the NIC is enabled and shows a valid IP address.
Check that DHCP or static addressing is correct.
Verify the network cable or Wi-Fi link is active.
If using VLANs, ensure the port is assigned to the correct VLAN.

1.2 Ping Tests

From the workstation, test in this order:

Ping own IP address
Ping default gateway
Ping another workstation on the same subnet
Ping the server (IP first → hostname second)

If local tests fail, the issue is LAN or NIC related.
If hostname fails but IP succeeds, DNS is the problem.

2. DNS and Name Resolution

2.1 Check DNS Settings

DNS servers should come from DHCP or be manually correct.
Ensure no public DNS (8.8.8.8 or 1.1.1.1) is overriding internal resolution unless intentionally configured.

2.2 Test Hostname Resolution

Use:

nslookup servername ping servername

Missing or incorrect DNS entries will break SMB, SQL, RDP, and almost all Windows-based communication.

2.3 Verify Hosts File

Check C:\Windows\System32\drivers\etc\hosts for incorrect manual entries.

3. Firewall and Security Policies

3.1 Windows Firewall

Verify that required services or ports are allowed on both:

Server
Workstation

3.2 Third-Party Security Software

Some endpoint security suites block:

SMB
Remote management ports
SQL
RDP
Application-specific ports

Temporarily disabling the security agent (if allowed by policy) is a useful diagnostic step.

3.3 Group Policy Restrictions

Check for GPOs that affect:

Network discovery
Credential delegation
NTLM/SMB restrictions
Windows Defender Firewall policies

4. SMB, File Sharing, and Authentication

4.1 Required Services

Ensure the following services are running on both devices:

Server
Workstation
TCP/IP NetBIOS Helper

4.2 Required Ports

SMB and Windows file sharing use:

TCP 445
TCP 139
UDP 137–138

4.3 Test Access

\\server-IP\share
\\hostname\share
net use \\server-IP\c$ /user:domain\user password

4.4 Check Credentials

Verify user permissions
Clear cached credentials if necessary
Check if the server denies admin shares (C$, D$)

5. SQL Connectivity

5.1 Test Using UDL

.udl file test confirms SQL server is reachable and authentication works.

5.2 Verify SQL Ports

Default port: 1433
Dynamic ports may require checking SQL Browser service.

5.3 Connection String Issues

Incorrect server names or instance names will cause failures even if network access is working.

6. RDP Connectivity

6.1 Confirm RDP Enabled

Check Remote Desktop settings on the server.

6.2 Firewall

Ensure port 3389 is open.

6.3 Licensing or Session Limits

Servers may block new sessions if:

RDS licenses are consumed
Max sessions reached
User not allowed to log in remotely

7. Application-Specific Troubleshooting

7.1 Check Required Services

Some applications require background Windows services or custom ports.

7.2 Verify Correct Server Application Version

Mismatched client and server versions can prevent communication.

7.3 Logs

Check:

Windows Event Viewer
Application logs
Service logs

8. Performance and Latency Tests

8.1 Extended Ping

ping server -t

8.2 Test for Packet Loss

pathping server

8.3 Test Port Reachability

Use PowerShell:

Test-NetConnection -ComputerName server -Port 445
Test-NetConnection -ComputerName server -Port 1433

This quickly identifies firewall or routing problems.

9. Routing and VLAN Issues

9.1 Confirm Gateway Routing Rules

Incorrect routing tables cause cross-subnet failures.

9.2 Check Inter-VLAN Rules

Firewalls or Layer 3 switches may block:

SMB
RDP
SQL
ICMP
Custom application ports