2.10. Client OS IP Parameters

💡 First Principle: When a user says "the internet is broken," the first question is: does the device even have valid network settings? Verifying IP parameters tells you whether the problem is on the client (no IP, wrong gateway) or somewhere else (server down, routing issue). This is step one in every troubleshooting workflow.

Consider this scenario: A user can't reach any websites. You check their IP configuration and see 169.254.45.67. That's an APIPA address—the client tried to get an address from DHCP and failed, so Windows auto-assigned a link-local address. The problem isn't the website, it's the DHCP server (or the path to it). Without checking IP parameters first, you might spend an hour troubleshooting the wrong thing.

What each parameter tells you:

IP address: Can this device send packets? (169.254.x.x = DHCP failed)
Subnet mask: Can it calculate what's local vs remote?
Default gateway: Does it know where to send non-local traffic?
DNS: Can it resolve names to IP addresses?

Verification Commands by OS:

OS	Command	Shows
Windows	`ipconfig`	IP, mask, gateway
Windows	`ipconfig /all`	Above + DNS, MAC, DHCP lease
macOS	`ifconfig`	IP, mask
macOS	`networksetup -getinfo <interface>`	IP, gateway, DNS
Linux	`ip addr` or `ifconfig`	IP, mask
Linux	`ip route`	Gateway
Linux	`cat /etc/resolv.conf`	DNS servers

Windows Example Output

C:\> ipconfig /all

Ethernet adapter Ethernet0:

   Connection-specific DNS Suffix  . : company.com
   Physical Address. . . . . . . . . : 00-1A-2B-3C-4D-5E
   DHCP Enabled. . . . . . . . . . . : Yes
   IPv4 Address. . . . . . . . . . . : 192.168.1.100
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 192.168.1.1
   DNS Servers . . . . . . . . . . . : 192.168.1.10
                                       8.8.8.8
   DHCP Server . . . . . . . . . . . : 192.168.1.1
   Lease Obtained. . . . . . . . . . : Monday, January 19, 2026 9:00:00 AM
   Lease Expires . . . . . . . . . . : Tuesday, January 20, 2026 9:00:00 AM

⚠️ Exam Trap: If a Windows client has a 169.254.x.x address, DHCP is enabled but failed to get an address from a server. Check DHCP server availability and network connectivity.