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Joe B.

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Specialities: Home networking, Wi-Fi routers, switches, Windows/macOS Ethernet issues, DHCP & IP configuration, D-Link DIR-series

Fix D-Link Wi-Fi works but LAN doesn’t — Ethernet no internet, LAN ports not working, DHCP missing, AP/port isolation

Technician avatar Technician
Hi! We’ll sort out the D-Link LAN not working issue. To target the right steps, tell me: what exact model (e.g., DIR-882/878/825)? Does Wi-Fi have internet while Ethernet/LAN PCs show “Unidentified network” or “No internet”? On the router, do the LAN port LEDs light up (green/amber) when a cable is plugged in? And are any devices going through a separate D-Link switch or wall jacks?
Customer
Model is D-Link DIR-878. Phones on Wi-Fi work fine — streaming, web browsing, everything. But two desktop PCs on Ethernet say “No internet, secured” or sometimes “Unidentified network”. LAN LEDs blink on the ports but Windows shows a 169.254.x.x address. I tried different cables and ports; same result.
Technician avatar Technician
Thanks — that 169.254.x.x (APIPA) means the PC isn’t getting an address from DHCP. Because Wi-Fi has internet, the WAN side and routing are fine; the problem is the LAN bridge/DHCP on the D-Link or port isolation. We’ll verify four things: (1) the LAN switch/bridge is enabled, (2) the router’s DHCP server is on for 192.168.0.0/24, (3) no port isolation / guest zone isolation is blocking LAN→LAN, and (4) link speed/duplex isn’t stuck at 10/half.
Customer
Where do I check those on the DIR-878? I can log into http://192.168.0.1. Wi-Fi clients show 192.168.0.x via DHCP, but the wired PCs keep getting APIPA. One PC sometimes gets 192.168.0.102 but still shows “No internet”.
Technician avatar Technician
Great — log in and do this on the D-Link web UI (DIR-878 layout):

Step A — Verify LAN bridge & DHCP
1) Go to Settings → Network. Confirm Router IP is 192.168.0.1, Subnet /24, and DHCP Server is Enabled with a pool like 192.168.0.100–199.
2) Click Connected Clients: do wired MACs appear at all? If they show up but have no IP, toggle DHCP Server Off → Save → On → Save to restart the service.
3) If you use Guest Zone, make sure “Enable Client Isolation” is off for the main network. Some models also have Port Isolation per-LAN — ensure it’s disabled so LAN→LAN and LAN→WAN traffic isn’t blocked.

Step B — Port/link sanity check
• Try another LAN port (1–4) and a known-good Cat5e/6 cable.
• In Advanced → Port Settings (if present), set speed to Auto (Auto-Negotiation). Avoid forcing 100/10 half-duplex.
• On Windows, run: ipconfig /release → ipconfig /renew → ipconfig /flushdns. You should get a 192.168.0.x address and gateway 192.168.0.1.
Customer
DHCP was enabled but the range started at 192.168.0.2 and ended at 192.168.0.50 — pretty small. I extended it to .2–.199 and toggled DHCP off/on. Now one PC picked up 192.168.0.110 with gateway 192.168.0.1, but it still says “No internet”. The other PC still gets 169.254.
Technician avatar Technician
Progress! One client now gets DHCP. Let’s confirm LAN→WAN routing and DNS.

Step C — Test gateway & DNS on the working PC
1) Open Command Prompt as admin and run:
  • ping 192.168.0.1 (router LAN) — should reply.
  • ping 8.8.8.8 (raw internet) — confirms routing/NAT.
  • nslookup dlink.com — confirms DNS.
2) If 8.8.8.8 works but domains fail, set router DNS to known good (e.g., ISP default or 1.1.1.1 / 8.8.8.8) under Settings → Internet.

For the second PC (still APIPA):
• Move its cable to a different LAN port (swap with the one that works).
• In the NIC properties, temporarily set a static: IP 192.168.0.210, Mask 255.255.255.0, Gateway 192.168.0.1, DNS 1.1.1.1. If that brings internet, the issue is DHCP on that port/cable; we’ll then return it to automatic.
Customer
Pings to 192.168.0.1 and 8.8.8.8 work on the first PC. nslookup failed until I set 1.1.1.1 as DNS on the router; after that, websites load. The second PC worked after I moved it to LAN port 2 — looks like LAN port 3 is flaky.
Technician avatar Technician
That explains it: one misbehaving LAN port plus DNS misconfigured. Two more hardening steps and we’ll be done.

Step D — Firmware & isolation checks (D-Link)
• Check for a firmware update (DIR-878: browse to dlinkrouter.local or 192.168.0.1; version shows at the top-right; update if newer). Firmware often fixes LAN ports not working and stability issues.
• Make sure Access Point Mode is disabled unless you intentionally use it. In AP mode, routing/DHCP may differ and wired clients can behave oddly if another router on the network is handing out IPs.
• If you have a D-Link switch inline, ensure no port isolation or VLAN is enabled there; use Auto-Negotiation and try another switch port.
Customer
I updated firmware and confirmed it’s not in Access Point Mode. Moved the cable on the switch too. Now both PCs get 192.168.0.x and internet is up. Anything else I should tweak so LAN stays stable?
Technician avatar Technician
Nice work — classic case of Wi-Fi works but LAN doesn’t resolved. To keep it that way:

• Leave DHCP enabled on the D-Link with a generous range (e.g., .100–.199). Avoid static IPs inside the pool.
• Keep DNS either “Obtain automatically” from ISP or set reliable public DNS (1.1.1.1 / 8.8.8.8).
• Label the known-good LAN ports and replace any suspect cable; prefer Cat5e/6.
• Schedule a monthly check for firmware updates. Many D-Link builds improve LAN stability and fix odd port behavior.
• If you add a managed switch later, ensure no VLAN/port isolation separates wired clients from the router.
Customer
Got it. DHCP pool widened, DNS set, and I marked the good ports. Everything on Ethernet and Wi-Fi is working now. Thanks!
Technician avatar Technician
You’re welcome! Quick recap for D-Link LAN ports not working while Wi-Fi is fine: verify DHCP on 192.168.0.1, disable AP/port isolation, test cables/ports and Auto-Negotiation, fix DNS, and update firmware. If a LAN LED is dark or only one port fails, swap ports — it’s often a hardware or negotiation quirk.
Customer
Perfect. If it breaks again I’ll jump into chat. Appreciate the detailed walkthrough.
Technician avatar Technician
Anytime! If a colleague mentions Ethernet no internet on D-Link or LAN LEDs blinking but no IP, share this checklist — or start a chat with an expert and we’ll fix it live.

Quick answer: the accepted fix

Accepted fix when D-Link Wi-Fi works but LAN doesn’t: keep the WAN/Wi-Fi as is, then restore LAN DHCP on 192.168.0.1, disable AP/port isolation, ensure LAN ports are on Auto-Negotiation, swap to a good port/cable, and set reliable DNS. Update D-Link firmware and expand the DHCP pool so wired clients consistently receive IP and internet.

Why D-Link LAN stops while Wi-Fi works (DHCP, isolation, link speed)

Typical causes of LAN ports not working on D-Link include a disabled or mis-scoped DHCP server (wired clients fall back to 169.254.x.x), port isolation or Guest Zone isolation that blocks LAN→LAN/WAN, bad cables, or forced 10/100 half-duplex leading to packet loss. Less often, a buggy build requires a firmware update to stabilize the internal switch.

Because Wi-Fi works but Ethernet has no internet, focus on the LAN bridge and DHCP path. Verify the router hands out 192.168.0.x to wired clients, gateway 192.168.0.1, and DNS resolvers that actually answer.

How to tell if it’s LAN, DHCP, or DNS

On a wired PC: if ipconfig shows 169.254.x.x, the DHCP server didn’t respond. If you get 192.168.0.x but sites fail, try ping 8.8.8.8 (routing/NAT) then nslookup (DNS). If routing works and DNS fails, set 1.1.1.1 / 8.8.8.8 on the D-Link or use ISP DNS. If only one LAN port fails, swap ports/cables; a blinking LED with no IP usually means negotiation or isolation.

D-Link LAN not working — quick troubleshooting tips

Wi-Fi OK? Fix the LAN bridge, DHCP, port settings, then DNS.

Fast path: Settings → Network — enable/expand DHCP on 192.168.0.1 → ensure no AP/port isolation on main SSID/LAN → use Auto-Negotiation for LAN ports → swap cable/port → set reliable DNS → firmware update. If a managed switch is present, disable unintended VLANs or isolation.

Disclaimer: This information is AI-generated and intended for general guidance only. For advice specific to your D-Link model and network, please consult a verified expert on Whizz-Tech before making decisions.

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FAQ

Why does Wi-Fi work but D-Link LAN doesn’t?

Usually the WAN/Wi-Fi path is fine but the LAN bridge or DHCP is misconfigured. Common culprits: tiny/disabled DHCP pool, port isolation/Guest Zone isolation, bad cable/port, or forced 10/100 half-duplex. Update firmware, expand the DHCP range, and keep LAN ports on Auto-Negotiation.

How do I fix D-Link “LAN ports not working” quickly?

On 192.168.0.1: enable and widen DHCP, disable AP/port isolation, confirm gateway/DNS, swap to a known-good LAN port and cable, then update firmware. On the PC, ipconfig /release → ipconfig /renew to grab a new lease.

What if only one Ethernet port has no internet?

Swap the device to another LAN port. If that fixes it, mark the flaky port and keep using the good ones. If multiple ports fail, check for managed switch VLANs or isolation and perform a firmware update/reset with your settings backed up.

Do I need Access Point Mode?

Only if another router is your gateway/DHCP. In most homes the D-Link should stay in Router mode so LAN/Wi-Fi share one 192.168.0.x network with DHCP from the D-Link. AP Mode can change DHCP behavior and confuse wired clients if not planned.

Sources

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