What you will achieve

Fix Self-Assigned IP on Wi‑Fi or Ethernet so your Mac gets a proper address from DHCP.

A self-assigned IP (169.254.x.x) means your Mac joined the link layer but never received DHCP lease. The fault may be Mac preferences, router DHCP pool, cable, or enterprise 802.1X — not always “Wi‑Fi broken”. Fix DHCP path before assuming hardware death.

1) Confirm the symptom

System Settings → Network shows yellow status and IP like 169.254.x.x — link is up but DHCP failed.

2) Quick resets

Toggle interface off/on.
Restart Mac and router/switch.
Try another cable or port for Ethernet.
Forget Wi‑Fi network and rejoin.

3) Renew DHCP lease

Network → Wi‑Fi/Ethernet → Details → TCP/IP.
Set Configure IPv4 to Using DHCP.
Click Renew DHCP Lease.

4) Remove stale preferences

Create a new Location: Network → Locations → Edit Locations → +. If fixed, old location plist was corrupt — delete the old location after backup.

5) Deeper causes

Router DHCP pool exhausted — reboot router or expand range.
Duplicate static IP on network.
Faulty USB-C dock or adapter — test direct connection.

6) USB-C dock and bridge chips

Self-assigned IP on Ethernet through cheap docks often means dock firmware hung — unplug dock power, Mac, wait thirty seconds. Test built-in Wi‑Fi vs dock Ethernet to isolate. Update dock firmware from vendor if available.

7) Manual IP temporary test

Set Configure IPv4 Manually with IP 192.168.1.200, router 192.168.1.1, DNS 192.168.1.1 — if connectivity returns, DHCP server or relay on router is broken, not Mac. Revert to DHCP after test.

8) Keychain and 802.1X

Enterprise Wi‑Fi with certificate rotation may leave stale 802.1X identity — delete network in Keychain Access searching SSID name, then rejoin and re-enter credentials.

Verify

Network status green; IP in router’s LAN range; internet and local resources work.

Additional troubleshooting notes

If steps above do not resolve the issue on the first attempt, reboot once, confirm System Settings → General → Software Update is current, and retry with a second administrator account to rule out profile or keychain corruption in your daily user. Document exact error text from Console.app with timestamp — vague “it still fails” without logs wastes support time. On Apple Silicon, re-test after full shutdown (not just restart) because firmware and Thunderbolt controllers reset only on cold boot. Intel Macs should repeat test in Safe Mode to bypass third-party login items. Before erase or keychain reset, verify Time Machine or clone backup completed — batch 3 guides assume Monterey/Ventura/Sonoma/Sequoia paths in System Settings; search Spotlight for renamed panes if your macOS version labels differ slightly.