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The problem

After setting up my second router as WDS from the root one. Any device can connect and gets Internet access. But after a while, it fails to resolve an IP.

When I try to connect stays at "Obtaining IP address" forever.

Env

The second router is TP-Link Archer C8. I set up the WDS following this guide.

I can successfully access both the main router admin panel (192.168.1.1) and the WDS router panel (192.168.1.11).

What I tried

  1. Using the device MAC address.
  2. Different SSID names and LAN IPs.
  3. If I reboot the router it works; and after sometime it fails again.

Questions

What am I missing?

How does it work only the first time?

What else can I try?

Where I can find more logs?

sospedra
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    Try updating the firmware of both devices. Unfortunately, WDS modes aren't always compatible with different manufacturers, and sometimes even the same manufacturer but different models. – Tim_Stewart Oct 18 '20 at 22:22
  • ty for the reply, both fw are in the latest – sospedra Oct 22 '20 at 16:36
  • It seems like the DNS you are using has issues. Try to set the router to use for DNS `8.8.8.8` or `1.1.1.1`. – harrymc Oct 31 '20 at 08:55
  • @sospedra You have probably mixed up words in your question. Here, _fails to resolve an IP_ doesn't make sense because it is the job of the DNS server to "resolve" and it resolves domains to IP addresses. If by "losing internet access" you mean that connected clients lose the ability to visit websites like `http://superuser.com` but can visit IP addresses like `http://1.1.1.1` then it's a DNS issue. But _stays at "Obtaining IP address" forever_ suggests it's a DHCP issue and clients lose connectivity completely. – ManSamVampire Oct 31 '20 at 20:29
  • If it's a DNS issue, [the fix](https://superuser.com/questions/1594888#comment2436481_1594888) suggested by @harrymc above should be helpful; else [my answer](https://superuser.com/a/1598775) below is regarding a DHCP issue. – ManSamVampire Oct 31 '20 at 20:37

3 Answers3

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When I try to connect stays at "Obtaining IP address" forever

This suggests the issue is DHCP unable to function for your repeater's WiFi network. Please clarify in the question, if I am wrong.

What am I missing?

From my personal experience, TP-Link's WDS Bridging feature does not actually bridge on the Layer 2 (Data link layer). Instead, it uses MAC Address Translation (MAT or sometimes, also known as ARP NAT) to connect devices from the repeater to the main router. The advantage of this approach (over 4-address mode) is that the main router doesn't have to support 4-address mode; hence it makes the repeater compatible with all routers.
However I am not sure if this is valid for your TP-Link Archer C8 as well. If your main router shows you an ARP table, you can check the entries in it to confirm.

How does it work only the first time?

I'm going to make a wild guess here and say it could be one of these reasons (though I could be completely wrong and the reason could be something else) -

  1. The DHCP server on your main router uses the actual MAC address (from which it received the request) to allocate addresses. Now, due to MAT, all the devices connected to the repeater have a single MAC address on the main router; and hence only a single address can be allocated to it.
    Try temporarily replacing your main router with something else and check if the issue persists.

  2. The DHCP relaying on the repeater is flawed and it is not properly relaying DHCP requests.
    You can try contacting TP-Link support, explain them the issue and ask for a firmware update.

What else can I try?

  1. Separate DHCP servers for main router and the repeater
    If you currently have the main router's DHCP server allocating, say 50 addresses, you could reduce it to, say 25 and enable another DHCP server on the repeater and make it allocate the rest 25 addresses. Just ensure the ranges don't intersect with each other and the default gateway provided by both is the correct router's address.

  2. Use a DHCP server only on the repeater
    Disable the DHCP server on the main router and make only the repeater handle DHCP for all devices.

  3. Use the DHCP Relay function on the repeater
    This usually complicates simple stuff and hence I ask you to try this as a last resort - Enable DHCP Relay on the repeater and enter the address of the main router as the server.

Where I can find more logs?

Usually there are logging settings in the web user interface of routers of various manufacturers, check those and enable logging for both routers. You might want to set the logging level to maximum detail (verbose) to help diagnose the issue.

ManSamVampire
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The router does not itself resolve DNS queries, but sends a query to an internet server. Usually this server is supplied by the ISP and is automatically received when the router connects to the ISP.

If the DNS server of the ISP has issues, try to set the router to use another DNS server. Useful ones are 8.8.8.8/8.8.4.4 (Google Public DNS) or 1.1.1.1 (Cloudflare).

harrymc
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Q. How does it work only the first time? Answer: When you turn on your router it scans nearby signals and connect to which it was configured to connect when main router signals are enough for a moment.

Q. What I am missing? Answer: When The signals of your main router fluctuate then secondary router disconnects from it. And when this happens the secondary router is unable to resolve DNS. You main router's signals might be very weak in that area.

Q. What else can I try? Answer: Go to wifi setting of your mobile or PC. Look for the saved networks and assign a manual DNS server there e.g. 8.8.8.8, 8.8.4.4 Then your device will connect to secondary router. But it will have no internet connection. Then open your secondary router settings and scan main router and change physical position of secondary router to get better signal for stable connection. And change channel of your main router if it is conflicting with any nearby router.

Q. Where I can find more logs? Answer: (WiFi Analyzer and Secondary Router) Install WiFi Analyzer in your mobile and go near the secondary router and check signals of your main router. And after connecting to secondary router by scanning signals.

MOHSIN SHAHZAD
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