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How to fix not appearing on sdr.hu if the DNS lookup doesn't match Kiwi's detected external IP?

edited August 2018 in Problems and Issues
I've been looking around for an answer to this, but I can't quite find an answer - or anything that works.

There is a KiwiSDR at the Northern Utah WebSDR site (since February) and I've not been able to make it "public" via sdr.hu because the public address that the Kiwi sees is NOT the same address that appears on the Internet - and the sdr.hu rejects it. The internet hostname for this receiver (which always works) is "kiwisdr1.utahsdr.org". Some sort of multiple NAT-ing and the fact that the Kiwi is inside a layer or two of virtual network(s) seems to be the reason for this.

Using "no-ip" doesn't work because it simply uses the public address that the KiwiSDR "sees" (which is wrong!): There doesn't seem to be a way to force it to use the host name to derive the IP (which would work) rather what the Kiwi's DUC passes to it as the problem is usually that the IP can change randomly in most cases where you would use this service. While I could try the "proxy.kiwsdr.com" reverse proxy, I'm not convinced that this will actually help, not knowing exactly what information is exchanged.

I'm working with the network admin and may eventually get this solved, but it has been a very slow process.

Any suggestions?

73,
Clint
KA7OEI

Comments

  • @kd2om had a similar problem
  • The only known fix for this is to use a real domain (not DDNS) to point to the Kiwi's actual public ip (that it senses and that sdr.hu sees). Or to use the kiwisdr proxy service which also proxies sdr.hu registration. The requirement for the ip address of sdr.hu registration packets to match the resolved ip address of the Kiwi's domain name is an sdr.hu policy that I cannot change (since I don't run sdr.hu).
  • Hello John,

    Because the IP address is "fixed" in that situation, I suppose that one could override what the Kiwi saw as the "external" IP address and put it in manually - but this is probably an edge case and is unlikely to be common.

    The problem is now fixed, but by manually changing what the Kiwi sees as its external network so that they now agree - a bit of a kludge, but it does solve the problem.
  • jksjks
    edited August 2018
    If we're just talking sdr.hu registration it doesn't matter what the Kiwi sees as its external IP address. The only thing that matters is that the registration packet ip source address, as received by sdr.hu, matches the resolved ip address of the Kiwi's domain name contained in the registration packet. So if your ISP is doing something funny with multiple layers of NAT that's fine so long as they can tell you what your actual, final (static) public ip is going to be so you can bind it to your domain (using the tools of whoever is hosting your domain).

    Now if they're not giving you a static ip you have a problem because the Kiwi won't know the correct public ip to use with DDNS assuming you're using the Kiwi's built-in DUC.
  • I had the same problem and believe it was two things.
    One, I was running client update software on a laptop and when I took it to work it would show that IP address. Now I run the client update software 24/7 on a Raspberry Pi and took it off any other machine.
    As a GPS signal is hard to get close to the Kiwi install site. I tested a 50 FT length of coax and used a can lid as the ground plane which worked surprisingly well. After doing this test for one day my Kiwi showed back up on the SDR.hu map when previous attempts to get it to work over several months did not.
  • A clarification:

    What I got from sdr.hu was an error about "ip.address.a != ip.address.b" where IP addresses "a" was what "kiwisdr1.utahsdr.org" resolved to and "b" was the odd address that the Kiwi itself was getting as an external IP - which sdr.hu could have known about only if it had been conveyed to sdr.hu by the Kiwi itself.

    In other words, sdr.hu *does* seem to care if what the Kiwi "sees" as the external IP address and what the external host name resolves to don't match. This seemed to happen because of multiple NATing and the Kiwi getting its result from an DNS on the "internal" network.

    As noted, the network guru simply made it so that the Kiwi would now "see" its external IP address as being the same as that to which "kiwisdr1.utahsdr.org" resolved and the problem simply went away.
  • The error message from sdr.hu is actually backwards.

    In ERROR (your IP does not match URL, 1.2.3.4 != 5.6.7.8) 1.2.3.4 applies to the URL/domain and 5.6.7.8 is in the ip src field of the received registration packet. I originally expected the reverse and it took me a while to realize what was going on.

    What the Kiwi "sees" as the external ip address usually does not matter unless the Kiwi is directly connected to the public Internet via a non-NAT router, which is rarely the case these days. Any NAT or VPN process is going to re-write the source ip address field of the ip packet which is what sdr.hu is ultimately checking against. The URL/domain you register with on sdr.hu has to resolve to whatever public ip is assigned to the registration packet when it leaves the last NAT/VPN of your ISP (or other scheme). It's as simple as that.
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