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help debugging LAN -> WAN connection (lemmy.dbzer0.com)
submitted 7 months ago by to c/selfhosted@lemmy.world
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I have been seeing periodic drops in internet access from LAN connected devices lately (last 2 months), and I haven't been able to figure about exactly what is going on. There doesn't seem to be a pattern, and it resolves itself after a few hours.

  • I can access the internet from my router
  • All devices on LAN can reach each other, both wired and WiFi
  • All devices on LAN can reach router, both wired and WiFi
  • I haven't changed anything in router settings
  • I haven't added new devices to my local network
  • I can't find any IP conflicts
  • It's a simple flat network with two APs, a single switch, no VLAN separation
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[–] 3 points 7 months ago (9 children)

I'm not sure what you mean when you say that you're seeing "periodic drops". Like, you're sending pings from a wired-LAN device to somewhere on the Internet and not getting a response? Inbound TCP connections from the Internet aren't being forwarded to a device on the LAN?

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  • [–] [S] 2 points 7 months ago (8 children)

    Internet access from all devices in my house simply stops working entirely for a few hours, sometimes there's weeks between this happening, sometimes only a few days. But when this happens, I can still reach internet from my router without issue.

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  • [–] 2 points 7 months ago (2 children)

    Does restarting your router help in these moments? Might just be an underpowered router

    Do your devices use the router's DNS? If so is it still reachable? From the client? From the router machine?

    Might be some kind of DHCP bug too but I'm not well versed in it

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  • [–] [S] 1 point 7 months ago (1 child)

    Restart doesn't fix it unfortunately.

    I am using my routers DNS, and it's reachable from my laptop.

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  • [–] 1 point 7 months ago

    If you're using your router as DNS, it's using something else as DNS. Check those configs. One entry might be invalid or intermittently down. Try switching to another provider.

    Also check that you're actually using the router as the DNS. When you do an nslookup you can specify DNS server. Next time you have the issue try

    Nslookup example.com 9.9.9.9

    If that replies then it's not a network issue it's your DNS config, either locally or on the router itself.

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  • [–] 1 point 7 months ago (4 children)

    Okay. So, I don't know exactly what you're doing to test that, but I'm going to assume, say, trying to go somewhere in a Web browser.

    First off, I have occasionally seen problems myself where consumer broadband routers that have been on for a long time wind up briefly becoming unresponsive. Probably some sort of memory leak or something. So if you haven't rebooted the thing and seen whether all your problems magically stop showing up, I'd probably try that. Quick and easy.

    Okay. Say that doesn't do it.

    When you confirm that the router can reach the Internet during this period of outage, how are you doing that? Going to a management Web UI from a wired-LAN device and trying to ping some host on the Internet?

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  • [–] [S] 1 point 7 months ago (3 children)

    When you confirm that the router can reach the Internet during this period of outage, how are you doing that?

    it's a gl.inet brume2 running openwrt, I SSH into it and can ping outwards to anything and my speed test from the CLI tells me i have 900Mbit available

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  • [–] 1 point 7 months ago* (2 children)

    Ah, gotcha, cool. If it's OpenWrt and you have shell access, that should make it easier to diagnose. When you are checking that you don't have connectivity from your local LAN device, you tried pinging the same out-there-on-the-Internet host, and that failed?

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  • [–] [S] 2 points 7 months ago (1 child)

    Yes I use the same destination fro testing on my laptop and the router.

    I think I've narrowed it down to a DNS issue, I just don't know exactly what. I can ping outwards from my laptop when using IPs but not names. But my laptop can reach my DNS.

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  • [–] 2 points 7 months ago

    For whatever reason ISPs tend (at least in here) to be pretty bad at keeping their DNS services up and running and that could cause issues you're having. Easy test is to switch your laptop DNS servers to cloudflare (1.1.1.1, 1.0.0.1) or opendns (208.67.222.222, 208.67.220.220) and see if the problem goes away. Or even faster by doing single queries from terminal, like 'dig a google.com @1.1.1.1'.

    If that helps you can change your router WAN DNS server to something than what operator offers you via DHCP. I personally use opendns servers, but cloudflare or google (8.8.8.8, 8.8.4.4) are common pretty decent choices too.

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