What is a 169.254 address?
When a PC joins a network, it asks a DHCP server for an IP address. If no reply comes within a few seconds, Windows gives itself a temporary address between 169.254.0.0 and 169.254.255.255. This feature is called APIPA.
With that address the PC can talk only to other devices that also have one, and can't reach the internet or the company's servers. In practice: no network.
The most common causes
- The cable or port: the cable is unplugged or damaged, or it's in a port that isn't active (like the phone port on the wall).
- The wrong network: the switch port is on another network (VLAN) with no DHCP, such as the phone network.
- The DHCP server: the server is down, or it has run out of addresses to hand out.
- Wi-Fi: the PC joined the network but failed to authenticate (wrong password or an expired certificate).
How to diagnose it step by step
- Ask: do colleagues in the same spot have network? If nobody does, it's a wider problem (usually DHCP or the switch). If it's only them, it's their PC, cable or port.
- Check the light: the network port on the PC has a small light. If it's off, the problem is the cable or the port.
- Request a new address with the commands below.
- Check the wall jack: some walls have two jacks (DATA and VOICE). The cable must be in DATA.
- If everything checks out and it's still 169.254, escalate to the team that runs DHCP or the network.
The commands you need
ipconfig /all
ipconfig /release
ipconfig /renew- ipconfig /all: shows the current address, whether DHCP is on, and the DHCP server's address.
- ipconfig /release: gives the current address back.
- ipconfig /renew: asks DHCP for a new address. If it comes back as 169.254 again, the request isn't reaching the server.