If you cannot configure a server’s network settings correctly, the entire server might as well be a paperweight – no one will be able to connect to it, and any services it hosts will be unreachable. This chapter covers the three pillars of network configuration: IP addressing, DNS, and DHCP. For the CompTIA Server+ SK0-005 exam, you must understand how to assign and troubleshoot these settings so that servers can talk to each other and to users reliably.
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A simple way to picture Network Configuration and Connectivity
At the entrance of a sprawling apartment complex, a corkboard covered in handwritten unit numbers and names. Hundreds of tenants come and go, and the mailroom is the central hub for all delivered packages and letters. Each apartment has a unique unit number – that’s like an IP address, a unique identifier for every device on a network. The corkboard also has a directory that maps a tenant’s name to their unit number – that’s the Domain Name System (DNS), which turns human-friendly names like ‘print-server’ into numeric IP addresses. When a new tenant moves in, the property manager assigns them a vacant unit number and hands them a key – that’s Dynamic Host Configuration Protocol (DHCP), which automatically assigns IP addresses, subnet masks, and other settings to a device when it connects to the network. If the tenant wants to send a letter to someone in another complex, they drop it in the outgoing slot. The mailroom knows how to route it out of the building – that’s the default gateway, the device that connects the local network to the outside world (like the internet). Without this system, each tenant would have to figure out the address of every other tenant on their own, leading to chaos and lost letters. The analogy maps precisely to how servers, printers, and workstations communicate on a corporate network, using IP addresses, DNS, and DHCP to keep everything organised and working smoothly.
Network configuration is the process of telling a device, like a server, how to find and be found by other devices on a network. At the heart of this are three components: IP addressing, DNS, and DHCP. Let’s break each one down in plain English.
First, an IP address (Internet Protocol address) is a unique number assigned to every device on a network. Think of it as a street address for your server. IPv4 addresses look like 192.168.1.10 – four numbers separated by dots. Each number ranges from 0 to 255. For a server to send data to another server, it needs the destination IP address. Along with the IP address, you also need a subnet mask, which defines which part of the address identifies the network and which part identifies the specific device (the host). For example, a subnet mask of 255.255.255.0 means the first three numbers are the network ID, and the last number is the host ID. This helps the server know whether the destination is on the same local network or needs to be sent to a different network.
Next, the default gateway is the IP address of the router or device that connects your local network to other networks, including the internet. If a server wants to talk to a device outside its own subnet, it sends the traffic to the default gateway, which then forwards it along. Without a default gateway, the server can only communicate within its own subnet.
Now, DNS (Domain Name System) is like the phonebook of the internet. Instead of remembering long strings of numbers, we use human-friendly names like ‘webserver01.company.com’. A DNS server translates that name into the corresponding IP address. When a server needs to reach another server by name, it sends a query to a DNS server, which responds with the IP address. If DNS is misconfigured, servers can’t resolve names, and applications that rely on names (like web browsers or email clients) will fail.
Finally, DHCP (Dynamic Host Configuration Protocol) automates the assignment of IP addresses, subnet masks, default gateways, and DNS server addresses. Instead of manually typing these settings on every device, you run a DHCP server on the network. When a new device (like a server) connects, it broadcasts a request, and the DHCP server responds with an IP address from a pool called a scope. The assignment is temporary – it has a lease time, after which the device must renew. For servers that always need the same IP (like a web server), you can create a reservation in DHCP that ties a specific IP to its network card’s MAC address (a permanent hardware identifier). Many organisations use DHCP for workstations but assign static IPs to servers to ensure they never change.
How it all works together: When you power on a server with DHCP enabled, it sends a DHCP Discover message. The DHCP server replies with a DHCP Offer (an available IP and settings). The server responds with a DHCP Request (accepting the offer), and the DHCP server sends a DHCP Acknowledgment. That’s the DORA process: Discover, Offer, Request, Acknowledge. Once the server has an IP, it can communicate. When it needs to reach another device by name, it uses DNS. To reach the internet, it uses the default gateway.
Why does this exist? Before DHCP, network administrators had to manually configure every device’s IP address, which was time-consuming and error-prone. DHCP eliminated that drudgery. Similarly, before DNS, we would have to remember IP addresses for every service – imagine having to type 192.168.1.100 to check email. DNS made the network usable for humans.
For the SK0-005 exam, you need to know how to configure these settings on both Windows Server and Linux. On Windows, you can set a static IP through the Network and Sharing Center or via PowerShell (New-NetIPAddress). On Linux, you use configuration files like /etc/network/interfaces or tools like nmtui. You also need to understand subnetting basics, because you may need to calculate whether two IPs are on the same subnet. Common exam scenarios include troubleshooting a server that can ping its own IP but not the default gateway, or a server that can’t resolve hostnames even though it has an IP. These point to misconfigured gateway or DNS settings.
Plan the IP Addressing Scheme
Before configuring any device, you need to decide which subnet (IP range) the server will use. This includes selecting a network address (e.g., 10.0.50.0/24) and ensuring the IP is unique. Document the IP, subnet mask, default gateway, and DNS servers you plan to assign.
Connect Physical Hardware
Plug an Ethernet cable from the server’s network interface card (NIC) into a switch port. Ensure the link lights are active – this confirms physical connectivity. Without this, no network configuration will work.
Configure the IP Settings Statically or via DHCP
Access the operating system’s network settings. For a server with a static IP, manually enter the IP address, subnet mask, and default gateway. For a server using DHCP, leave the settings on automatic. Choose static for critical servers to maintain consistent addressing.
Set the DNS Server Addresses
In the same network configuration window, enter the IP addresses of preferred and alternate DNS servers. This allows the server to resolve hostnames. If you leave it blank, the server can still use IP addresses but will fail on name lookups.
Verify Connectivity with Command-Line Tools
Run ipconfig /all to confirm the applied settings. Then ping the default gateway and a remote IP (like 8.8.8.8) to test local and internet reachability. Use nslookup with a known hostname to confirm DNS resolution. If any test fails, double-check the configuration for typos or mismatched subnet values.
Document and Test Application Access
Record the server’s IP and hostname in your network documentation. Create a DNS A record if needed. Finally, attempt to access the server from another device using its hostname to ensure end-to-end connectivity works for the intended service.
Let’s walk through a realistic scenario: you’re the IT administrator for a growing company that has just bought a new rack-mounted server to host a customer database. Your task is to configure its network settings so that employees can access the database from their workstations.
First, you physically install the server in the data centre and connect an Ethernet cable from its network interface card (NIC) to a switch port. You power it on and log into the operating system – it’s a Windows Server 2022 installation. The server initially tries to use DHCP because that is the default. But you know that database servers must have a static IP address so that clients always know where to find it. If the IP changed after a DHCP lease renewal, users would lose connectivity.
You open the network adapter settings and choose to set a static IP. You know your company uses the 10.0.50.0/24 subnet (with a subnet mask of 255.255.255.0). The default gateway is 10.0.50.1 (the router). You assign the server IP 10.0.50.10. You also configure the DNS server address – your company runs its own DNS server at 10.0.50.5, and uses a public fallback like 8.8.8.8.
Next, you create a DNS A record (Address record) in your DNS management console. This maps the server’s hostname (e.g., dbserver01.company.local) to its static IP 10.0.50.10. Now, when a user types \\\\dbserver01 in their file explorer, Windows will query the DNS server, get the IP, and connect.
You also check that the DHCP server (which runs on a separate server) will not assign 10.0.50.10 to any other device. To avoid conflicts, you create an exclusion range. Or you might set a DHCP reservation for the server’s MAC address, which gives the same effect without making the server statically configured – but for a database server, true static is usually preferred.
After configuration, you test connectivity:
Ping the server’s own IP (127.0.0.1 is loopback; better to ping 10.0.50.10) to confirm the NIC is working.
Ping the default gateway (10.0.50.1) to ensure you can reach the router.
Ping the DNS server (10.0.50.5) to verify network path.
Use nslookup dbserver01 to confirm DNS resolves correctly.
Finally, connect from a workstation using the hostname to access the database.
If any step fails, you diagnose: if ping to gateway fails, check the cable, switch port, or IP/gateway mismatch. If DNS lookup fails, check the DNS server address in the NIC settings or whether the A record exists. In practice, network configuration errors cause about 30% of server outages – so getting this right is critical. You document the IP assignment in your network map and server inventory so that future admins (or yourself) can easily troubleshoot.
An IT professional will also use tools like: - ipconfig (Windows) or ifconfig/ip addr (Linux) to view current settings. - tracert (Windows) or traceroute (Linux) to trace the path to a remote host. - netstat to see active connections. - DHCP server logs to see what addresses were leased.
Bullet list of common actions:
Assigning a static IP to a server from a specific subnet.
Configuring multiple NICs for redundancy or separate networks.
Setting up DNS forwarders to resolve external domains.
Creating DHCP scopes and reservations.
Troubleshooting with ping, nslookup, and pathping.
The SK0-005 exam tests your ability to configure and troubleshoot network settings on servers. The objective 1.3 specifically mentions IP addressing, DNS, and DHCP. Expect around 5–8 questions on this topic, many of them scenario-based. Here is exactly what they love to test.
Exam topics include:
Distinguishing between static and dynamic IP assignment.
Understanding the DORA process for DHCP.
Knowing what a subnet mask and default gateway do.
Identifying DNS record types: A, AAAA, CNAME, MX, PTR.
Troubleshooting steps when a server cannot connect: check IP config, ping gateway, check DNS resolution.
Configuring multiple IPs on one NIC (secondary IPs).
Using command-line tools: ipconfig, ping, tracert, nslookup, netstat.
Understanding DHCP lease times, scopes, reservations, and exclusions.
Traps the exam sets:
They might describe a server that can ping another device by IP but not by name. The correct answer is DNS misconfiguration – because IP connectivity is fine, but name resolution is broken.
They might ask: “A server can ping its own IP address but not the default gateway. What is the most likely issue?” Correct answer: the default gateway is wrong or missing, or the subnet mask is incorrect causing the server to think the gateway is on a different subnet.
They might list several DHCP failure symptoms: incorrect IP address (169.254.x.x) indicates APIPA (Automatic Private IP Addressing) – meaning no DHCP server responded.
They might ask which DHCP option must be set for internet access: option 3 – default gateway.
They might test the difference between a DHCP reservation and a static IP. A reservation tells the DHCP server to always offer the same IP to a specific MAC; a static IP ignores DHCP entirely.
Key definitions to memorise:
DHCP scope: a range of IP addresses that the DHCP server is authorised to lease.
Lease: the duration an IP address is assigned to a client.
Reservation: a permanent lease for a specific MAC address.
Exclusion: a range of addresses within a scope that DHCP should not assign.
DNS A record: maps a hostname to an IPv4 address.
DNS CNAME: maps an alias hostname to another canonical name.
When you see a question about “which command shows TCP/IP configuration”, the answer is ipconfig (Windows) or ifconfig (Linux). For “which command tests connectivity to a remote host”, it’s ping. For “which command shows the route packets take”, it’s tracert (Windows) or traceroute (Linux).
Always remember: the exam expects you to know that servers often require static IPs, while client workstations use DHCP. They also want you to be able to read an IP address and subnet mask to determine the network address and broadcast address – basic subnetting might appear as a single question.
Practice with scenario: “A newly installed server cannot reach the internet but can communicate with other servers on the same subnet. What is the problem?” Answer: default gateway not configured. “A server loses connectivity every 8 days. What might be the cause?” DHCP lease renewal issue – check lease time or the server is using DHCP instead of static.
Finally, the exam may present network diagrams or command outputs. Be ready to interpret ipconfig /all output to identify missing DNS servers or incorrect subnet masks.
Every network device needs a unique IP address to communicate, and the subnet mask is essential for determining whether a destination is local or remote.
DNS translates human-friendly hostnames into IP addresses; without it, users and applications must use raw IP numbers.
DHCP automates IP address assignment and provides other settings like default gateway and DNS server addresses.
Servers often require static IP addresses or DHCP reservations to ensure their address never changes.
The default gateway is the IP address of the router that connects your local network to other networks; without it, you cannot reach the internet.
The DORA process (Discover, Offer, Request, Acknowledge) describes how a DHCP client obtains an IP address from a DHCP server.
APIPA (169.254.x.x) appears when a DHCP client cannot contact any DHCP server, indicating a network or server failure.
Use ipconfig to view current IP configuration, ping to test connectivity, and nslookup to verify DNS name resolution.
These come up on the exam all the time. Here's how to tell them apart.
Static IP Address
Manually configured on the server and never changes.
Requires administrative effort to assign and document each IP.
Commonly used for servers that host services (web, database, file).
Dynamic IP Address (DHCP)
Automatically assigned by a DHCP server for a limited lease time.
Easy to deploy and manage for large numbers of devices.
Commonly used for workstations, printers, and less critical devices.
IPv4
32-bit address, written as four octets (e.g., 192.168.1.1).
Most widely used; supports up to 4.3 billion addresses.
Requires NAT (Network Address Translation) to conserve addresses.
IPv6
128-bit address, written as eight groups of hex (e.g., 2001:db8::1).
Provides an almost unlimited number of addresses.
Native support for end-to-end connectivity without NAT.
DNS A Record
Maps a hostname directly to an IPv4 address.
The most common record type for servers and websites.
Example: webserver01.company.com -> 192.168.1.10
DNS CNAME Record
Maps an alias hostname to another canonical hostname (not IP).
Used to point multiple names to the same server (e.g., www -> webserver01).
Example: www.company.com -> webserver01.company.com
DHCP Scope
A range of IP addresses that the DHCP server is authorised to lease.
Defines the pool from which clients receive IPs.
Example: 192.168.1.100 – 192.168.1.200
DHCP Exclusion Range
A subset of IPs within the scope that the server will NOT lease.
Used to reserve specific IPs for static devices outside DHCP.
Example: 192.168.1.1 – 192.168.1.10 excluded for routers and servers.
Mistake
DNS and DHCP are interchangeable services that both assign IP addresses.
Correct
DNS only resolves names to IP addresses; it does not assign addresses. DHCP automatically assigns IP addresses and other network settings.
Both acronyms start with D and are network services, so beginners lump them together.
Mistake
A server must always use a static IP address because DHCP is unreliable.
Correct
Many servers can safely use DHCP with a reservation, which gives the same stable IP without manual configuration. Static IPs are still common but not mandatory.
Early IT training often emphasises static IPs for servers without explaining that DHCP reservations are a modern, manageable alternative.
Mistake
The subnet mask is optional; you can leave it blank and the server will still work.
Correct
Every IP address must have a subnet mask. Without it, the device cannot determine which part is the network and which is the host, making it unable to route traffic correctly.
Many home routers automatically assign subnet masks via DHCP, so beginners never see them manually and think they’re not important.
Mistake
If a server can ping 8.8.8.8, then DNS is definitely working correctly.
Correct
Ping tests IP connectivity, not DNS. A server can ping Google’s IP but still fail to resolve names if DNS servers are misconfigured or unreachable.
Ping is the first troubleshooting step, so people wrongly assume success means everything is fine.
Mistake
A DHCP lease lasts forever once assigned.
Correct
DHCP leases have a finite duration (often 1–8 days). The client must renew before expiration. If it cannot, the IP is returned to the pool and the client gets a new one or loses connectivity.
Home networks often have very long lease times, so users rarely see renewal failures. In enterprise environments, short leases are common to free up addresses.
Reveal each answer, then mark whether you got it right. Score 60%+ to unlock the next chapter.
A subnet mask tells a device which portion of an IP address belongs to the network and which portion belongs to the host. Without it, the device cannot decide if another IP is on the same local network or if it must be sent to the default gateway.
On Windows, open Command Prompt and type ‘ipconfig’. On Linux, use ‘ip addr’ or ‘ifconfig’. The output will show the IP address, subnet mask, and default gateway for each network interface.
A static IP is manually set on the device itself and never changes. A DHCP reservation is configured on the DHCP server to always give the same IP to a specific device based on its MAC address; the device still uses DHCP but gets a fixed IP. Both achieve stable addressing.
APIPA stands for Automatic Private IP Addressing. The server automatically assigned itself an address in the 169.254.0.0/16 range because it was configured to use DHCP but could not contact a DHCP server. This usually means a network or DHCP server problem.
It depends on the DHCP server configuration. The default on many systems is 8 days, but administrators can set it from minutes to months. The client will attempt to renew after 50% of the lease time has passed.
Use the ping command followed by the target IP address (e.g., ping 10.0.50.1). If you get replies, the network path is working. If you get ‘Request timed out’, there may be a routing or firewall issue.
The default gateway is the IP address of the router that connects your local network to other networks, such as the internet. Without it, your server can only communicate within its own subnet.
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