# DNS Help



## fred974 (Jun 26, 2013)

Hi _e_veryone,

I bought my domain from 123reg and set my DNS entries with them instead of hosting my own DNS*.*

My problem is that I have made some changes to the DNS entries yesterday and since then, my server has been offline. When I contacted 123reg, I was told that it can take 24 to 48 hours for the new setting to fully propagate.

My question is: Can I set another DNS server on my box so my website is never offline if something happen to the DNS server on 123reg?

Can *I* have more than _one_ DNS server for a single domain?

Thank _y_ou all
Fred


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## kpa (Jun 26, 2013)

No you can't do anything until the changes to your DNS records are propagated trough the world and everyone using old copies of the DNS records have expired their copies when the TTL runs out. In the future you can prepare in advance by lowering the TTL of your DNS records to let's say 2 hours before you do any other changes and then wait for 2 hours before actually doing the changes. This guarantees that the changes you do will be in effect everywhere after 2 hours guaranteed.

You can have more than one DNS server for domain, it is a recommened practice in fact. In some cases it is required to have two servers and some registrars even require that the two servers can not be in the same network.


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## fred974 (Jun 26, 2013)

kpa said:
			
		

> No you can't do anything until the changes to your DNS records are propagated trough the world and everyone using those DNS records have expired their copies when the TTL runs out. In the future you can prepare in advance by lowering the TTL of your DNS records to let's say 2 hours before you do any other changes and then wait for 2 hours before actually doing the changes. This guarantees that the changes you do will be in effect everywhere after 2 hours guaranteed.
> 
> You can have more than one DNS server for domain, it is a recommened practice in fact. In some cases it is required to have two servers and some registrars even require that the two servers can not be in the same network.



Thank you very much for the info. Do you by any chance have a link that explain_s_ how to set[]up a secondary DNS?

Fred


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## kpa (Jun 26, 2013)

Start from here, the other material on the site is also a must read: http://www.zytrax.com/books/dns/ch6/index.html#slave


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## fred974 (Jun 26, 2013)

Thank you very much @kpa


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## usdmatt (Jun 26, 2013)

> In the future you can prepare in advance by lowering the TTL of your DNS records to let's say 2 hours before you do any other changes and then wait for 2 hours before actually doing the changes



Just to note, if your TTL was say 48 hours and you drop it to 2 hours, you will need to wait 48 hours before making the change, not 2.


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## kpa (Jun 26, 2013)

Yes of course sorry, not enough coffee yet...


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## gkontos (Jun 26, 2013)

usdmatt said:
			
		

> Just to note, if your TTL was say 48 hours and you drop it to 2 hours, you will need to wait 48 hours before making the change, not 2.



That is usually a problem with registrars that also provide free DNS. They don't always give you that control.


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## kpa (Jun 26, 2013)

No it's a general problem with DNS records if you set the TTL too high. You have to wait the time of the old TTL to be sure all the users of your DNS records have the records with the new TTL.


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## gkontos (Jun 26, 2013)

kpa said:
			
		

> No it's a general problem with DNS records if you set the TTL too high. You have to wait the time of the old TTL to be sure all the users of your DNS records have the records with the new TTL.



Did I say anything different here? How are you supposed to adjust the TTL if you don't have FULL control of your zone?


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## throAU (Jun 27, 2013)

Just one other thing on TTLs - this assumes that the provider implements your zone changes immediately.  If they don't, then the TTL will take effect from the time your change is processed internally to their server farm.

If it's a script - all good... if it's not, then good luck!


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