Getting 169 Invalid IP Address Range (APIPA) -Study Notes for PSC, SSC, and VSSC IT Exams

Welcome to the Computer Science Study tutorial by CoreNetworkZ EdTech Solutions, a trusted Mock Test and Competitive exam coaching platform. For candidates preparing for the SSC Scientific Assistant (CS & IT), VSSC Technical Assistant, and ISRO technical examinations, understanding IP addressing anomalies is crucial. One of the most common technical questions in these competitive exams involves the APIPA (Automatic Private IP Addressing) protocol.

Have you ever seen an IP address similar to 169.254.X.X on your computer? If yes, your computer runs on an APIPA. The 169 IP address is also called an invalid IP address. In this article, I will explain the concept of APIPA and how to fix it.

Let me explain the APIPA concept first. When a Windows computer fails to receive a valid IP address from a DHCP server, OS will automatically assign an Automatic Private IP address called APIPA.

This automatic Private IP address is in the range 169.254.0.1 to 169.254.255.254.




Since APIPA (169.254.X.X) is a private IP address, your computer will not communicate to any other devices with a valid IP address provided by a DHCP server.

In other words, your computer has no connection to a real network. A Device with a 169 IP Address range can only communicate with another APIPA device.

To communicate with other devices, you must change the 169.254.X.X IP address by fixing the issues that prevent it from getting a valid IP address.

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This tutorial explains the reasons for getting APIPA and how to resolve it.



Every Windows version like Windows 11, Windows 10, Windows 8, Windows 7, Vista, and XP support it except Windows NT. Follow the instructions below to fix 169.254.x.x addressing issues.

1. Release & Renew IP address
   
   When you notice APIPA on your computer, first try to release and renew the IP address from the command prompt. It will prompt your computer to contact the DHCP server. Commands to release and renew the IP address on Windows versions from XP are:
   
   
   • ipconfig/release
     
     
   • ipconfig/renew
   
   
2. Restart your computer
   
   
3. Ping the default gateway. If you are getting replies, try to go online. If not, follow the instructions
   
   
   • Check firewall settings & turn off all firewalls, including windows firewall
     
     
   • Check the configuration of all Internet security software products.
   
   
4. Power cycle the network
   
   
   • Disconnect the power cable from the router (DHCP server).
     
     
   • Reboot your PC
     
     
   • Reconnect the power cable to the router after 1 minute
     
     
   • Check the new IP address.
   
   
   
5. Assign a Static IP Address
   
   If your laptop does not change 169.254.x.x addressing, assign static IP to it according to the network address of the DHCP server. For example, if the address of the DHCP server is 192.168.1.1, you can assign a static IP address between 192.168.1.2 to 192.168.1.254.
   
   
6. If still having APIPA, use the  Following DOS prompt Commands.
   
   
   • ipconfig /flushdns
     
     
   • netsh int ip reset c:\tcp.txt
     
     
   • netsh winsock reset
   
   

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If you get APIPA On a wireless PC or laptop, the first step is to check whether the WiFi adapter or the Access Point is the source of the issue. If other devices on the WiFi network are working fine, you can ignore the steps on Router/AP.

In my experience, a faulty wireless adapter or corrupted WiFi utility installed causes this issue. Follow the steps below.

1. Unplug and replug the Wireless adapter (USB Adapters only).
   
   
2. Update Wireless adapter driver.
   
   
3. Uninstall and reinstall the wireless adapter driver.
   
   
4. Use Windows Wireless utility to manage the wireless connection.
   
   
5. Delete the preferred networks and connect again to the current wireless network.
   
6. Faulty WiFi Monitoring Utility
   
   A wireless computer can get APIPA due to a corrupted third-party WiFi monitoring utility installed.
   
   
   • APIPA On Windows 8 and 7
     
     To fix APIPA on Windows 11, Vista, and Windows 10 computers, follow the instructions provided in the link below. You can use WLAN AutoConfig instead of third-party utilities like Linksys Wireless Monitor or Dell WiFi utility.
     
     
   • APIPA on Windows XP
     
     If you are running Windows XP, you should follow the instructions below to override corrupted Belkin Wireless Network Monitor Utility or D-Link wireless utility.
     

SSC, DSSSB, and Kerala PSC conduct examinations for various IT posts.

Understanding APIPA is essential for candidates appearing for the DSSSB PGT/TGT Computer Science, Kerala PSC Degree Level Exam, SSC Scientific Assistant (CS), VSSC Technical Assistant, and System Analyst posts. These networking fundamentals are core parts of the Computer Science syllabus.

Kerala PSC Degree Level examinations have a Computer Science section where students can expect questions that require them to explain the reasons behind APIPA. You can check the Kerala PSC Degree Level Common Prelims Syllabus under the Computer Science section. I recommend you download the syllabus using this official link.

Reference: https://www.keralapsc.gov.in/sites/default/files/2021-02/syllubus.pdf

1. It can be useful when you do not have a DHCP server.
   
   
2. Even though your computer is assigned an APIPA, it will try to discover a DHCP server every five minutes.
   
   
3. The Subnet mask of APIPA is 255.255.0.0 (Class B network).
   
   
4. Computers having APIPA cannot communicate with devices in other subnets.
   
   
5. Two computers having APIPA can communicate with each other.
   

1. https://www.keralapsc.gov.in/sites/default/files/2021-02/syllubus.pdf
2. https://learn.microsoft.com/en-us/answers/questions/4010768/apipa