Strange DNS issues

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ashtonaut

346 posts

Ultimate Geek

# 175800 12-Jul-2015 13:36

I'm having some strange DNS issues and wondered if someone more knowledgeable than me might be able to help out.

I have a personal domain and a Spark residential account with a dynamic public IP. I use a free Cloudflare account as a dynamic DNS service to resolve vpn.mydomain.co.nz to my public IP. I run a couple of VPN servers on my home network
and update the Cloudflare DNS records every time my public IP changes, using a script on my Raspberry Pi and the Cloudflare APi.

Recently I've been noticing that quite often (but with no regular pattern), my domain is resolving to the wrong IP address. The IP address is always the same - 122.57.100.228. It's not just my personal connection that resolves incorrectly - sites like https://www.whatsmydns.net confirm that it's resolving to the wrong IP from multiple international locations. Throughout this time (a couple of weeks now), my public IP has remained constant.

I've done a bit of troubleshooting but haven't got anywhere yet.

First of all, is 122.57.100.228 an address with any significance or relevance within the Spark network? From what I can find online it's just a standard public address within Spark's pool.

There are a few things I have up my sleeve to try but would appreciate any comment on the IP address in question before I try something else...

insane

2411 posts

Uber Geek

Trusted

Subscriber

# 1341663 12-Jul-2015 16:41

Some of the 'whats my IP address' sites will detect whether you are being proxy'd, I believe www.whatismyip.com will advise if that's the case. May also pay to flick someone at Spark an email to see whether they are starting to do CG-NAT

ashtonaut

346 posts

Ultimate Geek

# 1341667 12-Jul-2015 16:47

No proxy detected using that site.

I have a suspicion that it might be Cloudflare's servers masking my real IP somehow within their DNS system, but it doesn't make sense that the issue is intermittent. Most of the time everything resolves fine, but it goes through periods where it might go bad once every few hours (I check every 5 minutes).

Perhaps someone from Spark can comment on CG-NAT or the specific IP mentioned above...

yitz

1426 posts

Uber Geek

# 1341678 12-Jul-2015 17:12

Er... you haven't set up the same DDNS host to update from two locations/connections have you?

122.57.100.x just looks like one of their Broadband dynamic ranges, not a infrastructure range for a proxy or anything.

Talkiet

4304 posts

Uber Geek

Trusted

# 1341691 12-Jul-2015 17:29

CG-NAT: No.
122.57.100.x - VDSL BB subscribers in Chch (Or connected to the Riccarton BNG anyway)

Cheers - N

Please note all comments are the product of my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

ashtonaut

346 posts

Ultimate Geek

# 1341726 12-Jul-2015 19:11

Talkiet: CG-NAT:

Oh. This doesn't sound good. From my limited understanding of CG-NAT, I don't want it (and it appears to be causing my current issues).

Talkiet: 122.57.100.x - VDSL BB subscribers in Chch (Or connected to the Riccarton BNG anyway)

This is my situation, so this is starting to make a bit more sense.

This raises a few questions:

1) Why does this appear to be intermittent? Using the getent or hosts command in Linux for vpn.mydomain.co.nz correctly resolves to my public IP almost all the time - but not all the time. Same with whatsmydns.net - most of the time all servers resolve to the correct IP - but not all the time. There doesn't appear to be any pattern - most of today has been fine, but then I had two issues within one hour this evening. Perhaps this is a vaguery of the DNS system that's beyond me - if so, fine.

2) Is there any way I can opt-out, request to be removed from this system, or similar? If this is here to stay and continues to cause these problems then it's going to be an issue for me - as far as I'm aware this hasn't been advertised (I don't recall it being noted anywhere when I signed up 9 months ago). I want a public IP - I'm happy for it to be dynamic, but it needs to be public.

3) Is this something specific to this geographic area, or to VDSL, or is Spark rolling this type of thing more widely?

Talkiet

4304 posts

Uber Geek

Trusted

# 1341762 12-Jul-2015 20:01

Read my post again... Specifically the word immediately after "CG:NAT:" on the first line!

Cheers - N

Please note all comments are the product of my own brain and don't necessarily represent the position or opinions of my employer, previous employers, colleagues, friends or pets.

ashtonaut

346 posts

Ultimate Geek

# 1341768 12-Jul-2015 20:15

One person supports this post

Haha, I assumed No was shorthand for 'number' and there was a line break issue...

Disregard my post, I take it all back :)

I do still have an issue, but it looks like I can rule out CG-NAT.

Further troubleshooting now required.

Cheers

ashtonaut

346 posts

Ultimate Geek

# 1341828 12-Jul-2015 21:52

yitz: Er... you haven't set up the same DDNS host to update from two locations/connections have you?

Almost certainly not, but I've reset my Cloudflare API key just in case.

BarTender

2958 posts

Uber Geek

Trusted

Lifetime subscriber

# 1342521 13-Jul-2015 19:53

Why don't you just get a static ip.. and be done with it??

and

ashtonaut

346 posts

Ultimate Geek

# 1342532 13-Jul-2015 20:10

BarTender: Why don't you just get a static ip.. and be done with it??

1) I enjoy the learning experience of getting these things to work
2) I'm too cheap to pay for one

After rebooting the modem to get a new IP address and resetting my CF API key, things seem stable after 24 hours - fingers crossed. Not sure which of those actions (or something else) has made the difference.