CloudFlare DNS Wierdness

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SamF

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#317795 15-Nov-2024 13:00

Hey guys,

I'm currently working with a customer who is using (free) CloudFlare as their DNS host.
However, I'm seeing some really weird DNS replication issues on their domain.

Yesterday morning, we changed the name servers from the existing pair of CF servers to another pair of CF servers as advised by the CF control panel, because the domain was not using the 'assigned' DNS servers.
Once we did this the CF control panel was happy and basically said everything was validated and good.

So we added a new TXT DNS record, which duly replicated globally (albeit a little more sluggishly than I was expecting - a few hours to complete)
However, late yesterday afternoon, there were issues with email sending and I discovered that a bunch of DNS records were no longer being replicated globally and things were looking pretty bad.

I left it overnight to see if it would settle, but things are actually looking worse this morning and it seems that as the day goes on we are actually LOSING replication of records and they are disappearing from servers globally!
I am currently in the process of migrating DNS hosting to another provider, but this whole incident is just weird.

I don't have any prior experience with using CloudFlare, but have you guys seen anything similar to this in the past?

Sam.

timmmay

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#3309385 15-Nov-2024 14:24

DNS doesn't replicate, it's cached based on the TTL / time to live. This change in thinking can help with problem diagnosis.

If you want to tell us the domain name we can take a look, otherwise not much we can do. I've found CloudFlare very reliable - I've been using them for many years. I have Certbot change DNS records, wait 20 seconds for the change, do a DNS lookup, in order to validate https certs so CloudFlare tends to work well for me.

CYaBro

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#3309387 15-Nov-2024 14:27

No issues here and we have many domains hosted on Cloudflare.
I've moved domains from one Cloudflare account to another, and changed the name servers and had no issues in the past too.

Opinions are my own and not the views of my employer.

fe31nz

1233 posts

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#3309503 15-Nov-2024 23:55

timmmay:

DNS doesn't replicate, it's cached based on the TTL / time to live. This change in thinking can help with problem diagnosis.

If you want to tell us the domain name we can take a look, otherwise not much we can do. I've found CloudFlare very reliable - I've been using them for many years. I have Certbot change DNS records, wait 20 seconds for the change, do a DNS lookup, in order to validate https certs so CloudFlare tends to work well for me.

I think Certbot is probably a bad example, as I am pretty sure it deliberately looks up the DNS from an authoritative DNS server, rather than using a normal caching relay lookup. The authoritative servers will be updated as fast as a network message transfer can be done (they normally are replicated from the primary DNS server), but normal lookups will still get the old values until the caching time expires.