macOS: Stuck on a Self-Assigned Address
A MacBook is on the office Wi-Fi with a 169.254 address and no default route. Read the interface, renew DHCP from Terminal, and verify. Work through it yourself in the live host terminal below.
Symptom
A MacBook is on the office Wi-Fi with a 169.254 address and no default route. Read the interface, renew DHCP from Terminal, and verify.
Your mission
Inspect, recover, then verify
Format
macOS Terminal
Investigate before you configure.
Use the CLI evidence to isolate the fault, make the smallest safe correction, then verify the network state changed.
Observe the symptom and link state.
Diagnose by comparing the protocol evidence.
Verify the expected device state and confirm the original symptom is resolved.
Console access: macOS
This workspace stacks for portrait phones. Rotate to landscape for the full split-screen console.
Need a hint?
Reveal the root cause when you're ready.
Try the investigation first, then use this as your escape hatch, not a dead end.
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Lab debrief
Turn the session into a repeatable troubleshooting pattern.
Use this reference after your attempt: first explain the symptom, then verify the evidence, then confirm the repair.
The problem
A MacBook joined the office Wi-Fi during a short DHCP server outage. The outage is over, the Wi-Fi icon shows connected, and nothing beyond the laptop is reachable.
What you'll practice
- Read an interface with ifconfig, including the hex netmask
- Recognise a 169.254.0.0/16 link-local address
- Check the default route with route -n get default
- Request a new DHCP lease with ipconfig set
- Confirm the new address with ipconfig getifaddr
The topology
One MacBook Air uses Wi-Fi interface en0 on the office WLAN, which leases 10.20.30.0/24 with gateway 10.20.30.1.
Commands to run yourself
The real diagnostic commands for this lab, copy-paste ready. Run these in the same order to reproduce the investigation on your own session.
ifconfig en0route -n get defaultTopology diagram
Fact-checked references
The commands and behaviour in this lab were checked against these primary references.
Frequently asked
Why is the netmask written as 0xffff0000?
macOS ifconfig prints IPv4 masks in hexadecimal. 0xffff0000 is 255.255.0.0, a /16, and 0xffffff00 is 255.255.255.0.
Does a Wi-Fi connection mean the network works?
No. It proves the Mac associated with the access point and passed its security checks. Addressing, the default route and DNS are separate layers and still need checking.
Is this the same as Windows APIPA?
Yes. Both follow RFC 3927 and pick an address in 169.254.0.0/16 when no DHCP server answers. The address only works for devices on the same link.
Ready to run this lab yourself?
No setup, no image sourcing. Book a session or ask for a live demo.