Journey to DNS Nirvana (maybe?)

During my various hikes through the woods of the internet, I came across DNS Spy one of the many dns checkers like, well, DNS Checker. But it offers constant monitoring like, for example Thousand Eyes.

codevamping.com is definitely a “vanity site” that I am not trying to monetize in any way. The only thing that would really be hurt if things go south is my ego. But DNS Spy offered a free scan, so why not.

Okay, thats not … bad.

Okay. Maybe I’m more attached to my ego than I thought. Let’s see if we can make DNS Spy happy and reach DNS Nirvana.

The detailed results of the scan are divided into 4 categories with warnings and recommendations for each section. Lets walk through them in turn.

Connectivity

Only one warning.

(Warning) No IPv6 reachable nameservers were found

Okkaaay. Hmmm. How would I fix this? Google Domains is my domain registrar, but the name servers are provided by Netlify. Netlify hosts this blog and it was just easier to let them handle the name services as well.

So, I head over to Netlify, open the dashboard for the codevamping domain (as opposed to the site) and - hey, what do you know - there is a big ol’ button “Enable ipv6”.

$ dig codevamping.com AAAA +noall +answer
codevamping.com.        20      IN      AAAA    2604:a880:400:d1::89c:7001

Well, there is a AAAA record, but can I resolve using ipv6 ?

$ dig -6 codevamping.com AAAA +noall +answer

; <<>> DiG 9.14.8 <<>> -6 codevamping.com AAAA +noall +answer
;; global options: +cmd
;; connection timed out; no servers could be reached

No. Interestingly, if I give the exact address of the ipv6 name server as defined in the router, I get:

$ dig -6 @2001:558:feed::1 codevamping.com AAAA +noall +answer
codevamping.com.        20      IN      AAAA    2604:a880:400:d1::89c:7001

So, I did what I wanted, but uncovered another issue. Apparently, none of my computers is picking up the ipv6 name servers via dhcp - or the router isn’t sending them, even though the configuration says to do so.

Performance

No warnings or recommendations. Moving on …

Resiliency and Security

(Warning) All IPv4 nameservers are hosted by the same provider

Well, yes. Netlify is a reseller for NS1. They would be happy to provide all sorts of redundancy for the right price. Not worth the price for me. I totally understand why you might want this if you are trying make money and can’t afford to go down.

(Warning) No DNSSEC records found.

After much searching on support forums and a couple emails, it turns out that Netlify does not support DNSSEC. This is actually a quite often requested feature.

I can’t fix this one.

(Warning) All the nameservers are being operated from a single domain (nsone.net).

See above about “same provider”.

(Recomendation) All IPv4 nameservers appear to be hosted in the same country (US). You might want to consider spreading the nameservers geographically.

See above about “same provider”.

Well, I won’t reach total Nirvana because I can’t afford it. Oh, well.

(Recommendation) No CAA records found.

CAA - Certification Authority Authorization is a statement about which Certificate Authorities can issue certificates for the domain. If CAA records are available for a domain, the CA is not supposed to issue certificates unless they are on the list. Also, user agents (web browsers) are supposed to reject a certificate if it is issued by a CA other than the ones on the list.

Netlify uses Let’s Encrypt for most of the customer side domains. The certificates issued are for both the apex domain (codevamping.com) as well as a wildcard for all subdomains (*.codevamping.com). The CAA records needs to give letsencrypt.org authority for both.

$ dig codevamping.com CAA
codevamping.com.        3600    IN      CAA     0 issuewild "letsencrypt.org"
codevamping.com.        3600    IN      CAA     0 issue "letsencrypt.org"
codevamping.com.        3600    IN      CAA     0 iodef "mailto:mhhollomon@gmail.com"

The iodef record tells the CA where to send reports that somebody asked them to issue a certificate and the CA was not on the list.

DNS Records

(Recommendation) No SPF records were found.

I had no clue what SPF - Sender Policy Framework record was.

The idea is simple enough. The SPF records says what computers can send email showing as coming from the domain in question. If the sending domain/ip is not listed in the SPF record for domain it claims to be coming from, many mail gateways will mark the message as spam. Or at the very least, the message will be marked as “via” the true sending domain as you can see below.

My outgoing email is handled by SendGrid. After all the reading I knew that I needed to add a SPF/TXT record that looked something like:

v=spf1 include:something.sendgrid.net ~all

which says that a computer on sendgrid.net can send email for my domain but nobody else (~all) can 1.

To be clear, there is an SPF RR type, but that is not what you want. Google will happily use those, but both dnsspy and dnschecker agree that the record type should be TXT So the dig session will look like:

$ dig codevamping.com TXT +noall +answer
codevamping.com.        3600    IN      TXT     "v=spf1 include:u14122663.wl164.sendgrid.net ~all"

Figuring out what that something was bit of a challenge. On the SendGrid console there was a “Verify Domain” wizard that led me through some steps including adding some CNAME records to my domain that pointed back to sendgrid.net. One of those records contained a hostname, that when I looked up the SPF record contained the ip address of the host that the emails were coming from. So, that is what I needed in my SPF record.

After that, it was a quick trip to Netlify to update the domain records.

Dig shows the SPF record, but to really test, I had to wait until the next status email came from the domain.

Nice! Completely white-labelled to my domain.

(Recommendation) No DMARC records have been found.

Needed to dig a bit about this one. This adds a cryptographic key to the SPF processing in order to help against DNS spoofing. SendGrid has a reasonable write up on it.

Another TXT record placed into my DNS via Netlify.

(Recommendation) No IPv6 record has been found on the zone apex (codevamping.com).

We took care of this as a part of ipv6 name server thing above. So, nothing more to do.

Rescan

I was able to fix a few things (SPF, DMARC, ipv6) and had to punt on some other things (DNS redundancy). Now, it was time for the retest…

Not much of an improvement. I thought at least I would get conenctivity up to 100%.

Wait… it is still saying that there are no ipv6 name servers.

$ dig dns1.p08.nsone.net. AAAA +noall +answer
$

Oh.

The name server assigned to my domain will serve AAAA for my domain, but they they themselves do not have AAAA records.

So, you can talk to my domain using ipv6, but you can’t query the ipv6 address using ipv6.

Thoughts

Well, I certainly learned more about DNS and email/spam. And I set things up better for my domain.

I think I’m going to have to transition back to using Google to name serve. That will clear up the ipv6 issue as well as allowing me to turn on DNSSEC.

I’m not going to diss Netlify though. They have done a great job hosting my website. But I’m glad I didn’t register my domain through them.

Hopefully this has been useful and thank you for sharing the journey - even if we didn’t make to the destination.


  1. To be exact the ~ means to “view with suspicion” - not totally reject. To get a reject, use a minus sign : - (hard spf check failure). ↩︎