OS Networking Configuration and Remote Access

OS Networking Configuration and Remote Access

Why These Skills Matter

Every IT support technician configures network settings, troubleshoots connectivity, and accesses machines remotely. Whether you are imaging a workstation, assisting a remote user, or managing a Linux server, you need to move fluidly between static and dynamic addressing, Windows Remote Desktop Protocol (RDP), and Secure Shell (SSH). These tasks appear on both the CompTIA A+ Core 2 and CompTIA Network+ exams and are daily duties on the job.

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IPv4 Addressing: Static vs. DHCP

Every device on a TCP/IP network needs three settings to communicate locally and reach the internet: an IP address, a subnet mask, and a default gateway.

• A static IP address is typed in manually and does not change unless you change it. Use static addressing for servers, printers, and infrastructure devices so their addresses stay predictable.
• DHCP (Dynamic Host Configuration Protocol) lets a DHCP server assign an address automatically. Most workstations and laptops use DHCP because it reduces administrative overhead.

Configuring a static address in Windows 10/11:

1. Open Settings → Network & Internet → Ethernet (or Wi-Fi) → your adapter → IP settings → Edit.

Alternatively, go to Control Panel → Network and Sharing Center → Change adapter settings, right-click the adapter, choose Properties, select Internet Protocol Version 4 (TCP/IPv4), and click Properties.

2. Enter the IP address, subnet mask, and default gateway provided by your instructor.

3. Enter DNS server addresses (for this lab, you may use the gateway or a public address such as the lab-assigned DNS).

4. Click OK to apply.

Verifying connectivity:

• `ipconfig` — displays the current IP configuration.
• `ipconfig /all` — shows full detail including MAC address and DHCP status.
• `ping <gateway IP>` — confirms Layer 3 connectivity to the router.
• `ping <peer IP>` — confirms connectivity to another lab machine.

To return to DHCP, go back into the adapter properties, select Obtain an IP address automatically, click OK, and run `ipconfig /release` followed by `ipconfig /renew` to force the lease immediately.

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Windows Remote Desktop (RDP)

Remote Desktop Protocol lets you control another Windows machine's graphical interface over the network. It runs on TCP port 3389.

Enabling Remote Desktop on the host machine (the PC you want to connect to):

1. Open Settings → System → Remote Desktop and toggle Enable Remote Desktop to On.

On older builds, use System Properties → Remote tab → select Allow remote connections to this computer.

2. Add the user account(s) that will be allowed to connect via Select users that can remotely access this PC.

3. Confirm Windows Firewall has automatically created an inbound rule for Remote Desktop (TCP 3389). Open Windows Defender Firewall with Advanced Security → Inbound Rules and verify the rule labeled Remote Desktop - User Mode (TCP-In) is enabled. If it is not, enable it manually.

Connecting from the client machine:

1. Open Remote Desktop Connection (search `mstsc` in the Run dialog or Start menu).

2. Enter the host machine's IP address and click Connect.

3. Enter valid credentials when prompted.

4. Work in the remote session, then choose Start → Disconnect — do not simply close the window without disconnecting, as that leaves the session active.

Safety note: Remote Desktop gives full control of another machine. Use only authorized lab machines and credentials. Unauthorized remote access to systems you do not own or have permission to access is a federal offense under the Computer Fraud and Abuse Act.

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SSH on Linux (Ubuntu)

Secure Shell (SSH) is the standard protocol for remote command-line access to Linux/Unix systems. It encrypts all traffic, including credentials. SSH listens on TCP port 22 by default.

Installing and starting OpenSSH server on Ubuntu:

```

sudo apt update

sudo apt install openssh-server -y

sudo systemctl enable ssh

sudo systemctl start ssh

sudo systemctl status ssh

```

The `systemctl status ssh` output should show active (running).

Connecting from Windows:

• Windows Terminal (Windows 10/11): `ssh username@<Ubuntu_IP>`
• PuTTY: Enter the host IP, confirm port 22, select SSH, click Open, and log in.

Accept the host key fingerprint on first connection — this fingerprint is stored so you are warned if it changes unexpectedly (a sign of a potential man-in-the-middle attack).

Three useful diagnostic commands to run in the SSH session:

1. `ip a` — shows network interface addresses.

2. `df -h` — shows disk usage in human-readable form.

3. `uptime` — shows how long the system has been running and load averages.

Log off cleanly with `exit` or `logout`.

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Documentation and Lab Safety

• Record every IP address, command, and result in your lab log as you go — do not reconstruct from memory afterward.
• Work only on machines assigned to you. Never attempt to SSH or RDP into a machine outside your lab subnet without explicit instructor permission.
• When finished, return all adapters to DHCP unless told otherwise, so the next class starts with a clean environment.
• If you are working inside a physical machine (cable routing, NIC installation), follow lockout/tagout procedures and ground yourself with an antistatic wrist strap before touching internal components. For this software-only lab, physical PPE is not required, but maintain tidy cable management to prevent trip hazards.