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I am having a problem with a domain having cached nameservers. It goes to the old website instead of the new in some areas. Am I able to go to the old hosting DNS and change the A record and get it to the new website? How long does this cache take to expire?

Lewis Menelaws
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  • depends on what ttls are set in the zone file that was queried when the cached entries were created. be sure serial, etc. are all updated on the master server. – ivanivan Feb 24 '18 at 16:36
  • @ivanivan I did a `dig trace` and got this back (as well as others). `515871 IN NS a.root-servers.net.` Does this mean I have to wait ~6 days for it to change? To be clear it shows the new website on other wifi networks just not mine or a couple others. – Lewis Menelaws Feb 24 '18 at 17:28
  • If you gave the true domain name, people would have been able to give you more relevant advices. – Patrick Mevzek Feb 27 '18 at 03:40

1 Answers1

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Am I able to go to the old hosting DNS and change the A record and get it to the new website?

Yes, this is exactly what you should do.

How long does this cache take to expire?

Short Answer

Wait a week.

Typically your transition period shouldn't last more than a few days, but it's rare to see ones that require an entire week. If you don't want to get into the technical details of how this process works, a week should be safe. A week also gives you time to notice anything catastrophically wrong with your new environment that might force you to "roll back" to the old servers.

Long Answer

I'm going to steer you to a closely related Q&A on this one:

Migrating DNS provider when having high NS-record TTL

When you log into your registrar control panel and change DNS servers, you enter into a transition period where any recursive DNS servers that are already aware of your domain must pick up the change. The only safe thing you can do is maintain both your old and new nameservers in an identical state until this period expires.

The duration of this transition period is the largest TTL associated with your domain in the delegation path. This would be the NS records living inside of the nameservers you control, as well as the delegation pointing to it. This is easier to explain visually, and you can find these values by either using the dig command on a UNIX/Linux box (dig +trace example.com), or using similar web based tools that provide the same functionality.

In the case of example.com, you should see output similar to the following:

.           233637  IN  NS  a.root-servers.net.
.           233637  IN  NS  b.root-servers.net.
.           233637  IN  NS  c.root-servers.net.
.           233637  IN  NS  d.root-servers.net.
.           233637  IN  NS  e.root-servers.net.
.           233637  IN  NS  f.root-servers.net.
.           233637  IN  NS  g.root-servers.net.
.           233637  IN  NS  h.root-servers.net.
.           233637  IN  NS  i.root-servers.net.
.           233637  IN  NS  j.root-servers.net.
.           233637  IN  NS  k.root-servers.net.
.           233637  IN  NS  l.root-servers.net.
.           233637  IN  NS  m.root-servers.net.
;; Received 228 bytes from 8.8.4.4#53(8.8.4.4) in 4 ms

com.            172800  IN  NS  h.gtld-servers.net.
com.            172800  IN  NS  l.gtld-servers.net.
com.            172800  IN  NS  a.gtld-servers.net.
com.            172800  IN  NS  f.gtld-servers.net.
com.            172800  IN  NS  c.gtld-servers.net.
com.            172800  IN  NS  m.gtld-servers.net.
com.            172800  IN  NS  i.gtld-servers.net.
com.            172800  IN  NS  k.gtld-servers.net.
com.            172800  IN  NS  g.gtld-servers.net.
com.            172800  IN  NS  e.gtld-servers.net.
com.            172800  IN  NS  d.gtld-servers.net.
com.            172800  IN  NS  j.gtld-servers.net.
com.            172800  IN  NS  b.gtld-servers.net.
;; Received 489 bytes from 192.112.36.4#53(192.112.36.4) in 32 ms

example.com.        172800  IN  NS  a.iana-servers.net.
example.com.        172800  IN  NS  b.iana-servers.net.
;; Received 165 bytes from 192.26.92.30#53(192.26.92.30) in 2484 ms

example.com.        86400   IN  A   93.184.216.34
example.com.        86400   IN  NS  a.iana-servers.net.
example.com.        86400   IN  NS  b.iana-servers.net.
;; Received 93 bytes from 199.43.135.53#53(199.43.135.53) in 22 ms

In the above output, we would ignore the TTLs associated with . and com., because those are not for our domain. The TTLs that interest us are the last two sets, which are both associated with example.com.. The first set is the delegation to the nameservers you had configured in your registrar control panel. The second set is the NS records that live on those DNS servers. To ensure a smooth transition you must use the larger of these two values, which is usually the delegation.

In the above example, your transition period would be 172800 seconds. (two days)

Andrew B
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  • If I set an `A` record on the old nameservers would they be able to go on the new website? Is this an ISP problem? I am only getting this through bell internet. – Lewis Menelaws Feb 26 '18 at 16:18
  • 1) Correct. 2) The impact is going to vary depending on how frequently your website is accessed by various ISPs. The heavier your website is utilized, the greater the probability that the old nameservers would have still been in the cache when your migration occurred. Even then, ISPs typically have regional DNS clusters and the impact will be tied to the regions that access your website most frequently. – Andrew B Feb 26 '18 at 20:56