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I need to set a wildcard DNS record for a sub domain which already has an A record. I'm not sure if i have to use a new A record for this or can just use a CNAME that points to the A record.

My script has the following domain structure

http(s)://{random_code}.{location_subdomain}.{domain.com}/{path}
  • {random_code} - We use random code as a solution against browser implemented HTTP socket limits. (only used for loading dynamic elements onto a page - as such it can only be viewed by viewing the source of a web page while the URL in a users browser only shows the location subdomain)
  • {location_subdomain} - We load content from our closest server to the user, so each location has an A record that points to a different server (content across all our location servers are 1:1).
  • {domain.com} - Points to our front end server which hosts our index page
  • {path} - self exploratory

Current DNS zone file

domain.org. 86400   IN  NS  dns1.domain.org.
domain.org. 86400   IN  NS  dns2.domain.org.
domain.org. 86400   IN  NS  dns3.domain.org.
domain.org. 86400   IN  NS  dns4.domain.org.
domain.org. 14400   IN  A   1.1.1.1
localhost   14400   IN  A   127.0.0.1
www     14400   IN  CNAME   domain.org.
ftp     14400   IN  A   1.1.1.1
france  3600    IN  A   2.2.2.2
phoenix 3600    IN  A   3.3.3.3
nl      3600    IN  A   4.4.4.4
*       14400   IN  A   1.1.1.1

But i need to add a wildcard for each location A record that points to the same address. So for example {randome_code}.phoenix.{domain.com} would point to 3.3.3.3 while still making sure phoenix.{domain.com} still points to the same IP.

Do i just have to create new A records like this for each location while keeping the non wildcard records as well? 

*.france    3600    IN  A   2.2.2.2
*.phoenix   3600    IN  A   3.3.3.3
*.nl        3600    IN  A   4.4.4.4

I was under the assumtion that this would be an extra lookup so i thought i would be able to use a CNAME but im not sure the proper format to add a wildcard CNAME record that points to an already created A record while still keeping the original wildcard working so that any lookup that are not using a location subdomain would still be answered with our front end web server address.

Or do i have this completely wrong, can i not have a wildcard on the root domain as well as on A records ?

Analog
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1 Answers1

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What you have there:

*.france    3600    IN  A   2.2.2.2

will work exactly as you're expecting; a query for abc.france.example.com will get the answer from the wildcard A record, while france.example.com will still be getting its data from france 3600 IN A 2.2.2.2.

No extra lookup is needed, as you're not doing additional delegation.

If it's easier for you to manage, you can also use a CNAME:

*.france    3600    IN  CNAME   france

A CNAME can typically cause an extra lookup, but in this case it won't; the record being referred to is in the same zone, so your DNS server will respond with the "answer" of the CNAME, as well as including the relevant A record for france.example.com.

Shane Madden
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  • I don't know if the wording is just a coincidence or if you meant to imply that the `A` record would be returned in the *additional section*? Anyway, it's returned in the *answer section*, together with the `CNAME` record. – Håkan Lindqvist Mar 29 '15 at 19:47
  • @HåkanLindqvist You're right, I was thinking `NS` record behavior - corrected. – Shane Madden Mar 29 '15 at 19:49
  • Perfect thank you for the explanation, i will be using a CNAME then. – Analog Mar 30 '15 at 17:25