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rDNS, how? (feddit.dk)
submitted 2 years ago by to c/selfhosted@lemmy.world
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I'm on at least 2 blocklists at this point for the crime of not having reverse DNS set up. I don't know how rDNS works. No amount of reading Wikipedia is helping me understand what I have to do.

  • I have a domain at a registrar which gives me bog standard DNS.
  • I have Apache running on my network.
  • I have PiHole running on my network.

My understanding is that rDNS is not set up at my registrar, but somewhere in my network. What do I do?

Thank you for your time.

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[–] 5 points 2 years ago (1 child)

Are you actually trying to send mail from your own smtp server? You mention apache and pihole which are completely unrelated.

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  • [–] [S] 1 point 2 years ago (1 child)

    No emails just routing issues.

    Copy pasted but I have routing issues that neither my ISP nor the people who suffer from it can pinpoint. I’m so far down this rabbit hole that I’m assuming my IP got on a blacklist that’s sitting on some random networking infrastructure and I’m just trying to resolve all blacklist issues on the off chance that it works.

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  • [–] 2 points 2 years ago (1 child)

    rDNS won't really help with that, it's just a DNS lookup that ties your IP to a hostname, typically used for mail server spam controls.

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  • [–] [S] 0 points 2 years ago (1 child)

    I'm desperate.

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  • [–] 2 points 2 years ago (1 child)

    Have you done any traceroute runs when the issue is happening to try and diagnose where the routing issue is occurring?

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  • [–] [S] 1 point 2 years ago (2 children)

    Copied this from another comment I made

    A number of people can’t route to me at all. My domain is drkt.eu and sits on port 80 and 443 @ 89.150.135.135 and 2a05:f6c7:8039::1337

    IPv6 is not big in my country, and I don’t think anyone afflicted has IPv6 so I can’t tell you if this affects both v4 and v6.

    It’s not a DNS issue, as the afflicted users can get the correct IPs from nslookup.

    Mullvad VPN users are consistently unable to route to me.

    One friend can’t route to me from his workplace network. It’s a small network and their admin claims they don’t block anything so it’s a mystery to him as well.

    Another friend across town can’t reach my network despite being so close to me hop-wise, but his network is run by wacks and is consequently also quite wack. I can’t confidently say this is the same issue.

    I’m not dropping any connections for any reason. My ISP claims they aren’t doing any blocking of domains or IPs.

    Traceroutes time out at consistent hops but it’s different per afflicted network. The only recurring name has been costumer.tdc.net

    It might not be related, but I can’t route to catbox.moe and their admin says my IPs are not blacklisted in any of their systems.

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  • [–] 1 point 2 years ago (1 child)

    Do you have a different firewall/router you can try? Even just plug your PC directly into the modem for now to bypass your router and rule that out.

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  • [–] [S] 1 point 2 years ago* (last edited 2 years ago) (2 children)

    Routing to me has been solved, my router was incorrectly dropping pings on WAN because I messed up the firewall configs. The trouble users still can't reach my website.

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  • [–] 1 point 2 years ago (1 child)

    Your ISP may block 80 / 443. Try moving your webserver to an alternate high port and ask the users to test with that.

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  • [–] [S] 1 point 2 years ago (1 child)

    But it's only very few people. If my ISP blocks these ports, why 99% of people have no issues?

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  • [–] 1 point 2 years ago (1 child)

    At this point I'd install wireshark and see if I'm getting their TCP connections at all.

    Given your other routing issues though, I would guess you have another config issue on your firewall.

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  • [–] [S] 1 point 2 years ago* (last edited 2 years ago) 
      5.186.33.87 > 89.150.135.135: ICMP echo request, id 1, seq 43476, length 40
12:38:19.843890 d0:50:99:81:48:17 > 4c:6d:58:4a:97:d4, ethertype IPv4 (0x0800), length 74: (tos 0x0, ttl 64, id 21715, offset 0, flags [none], proto ICMP (1), length 60, bad cksum 0 (->1dc0)!)
    89.150.135.135 > 5.186.33.87: ICMP echo reply, id 1, seq 43476, length 40
12:38:20.219177 d0:50:99:81:48:17 > 4c:6d:58:4a:97:d4, ethertype IPv4 (0x0800), length 43: (tos 0x0, ttl 64, id 32958, offset 0, flags [none], proto ICMP (1), length 29, bad cksum 0 (->3f6d)!)

    Packet capture from the router for 4 pings from him to me. 2 of 8 packets expected were captured and have bad checksums. Disregard, all 8 expected packets do show up

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