Domain Name Service and zone file

fliker09

Both in course material at 6.17 and in Lab 6, Exercise 6.2 where is admin.example.com. in SOA line. What for?

lee42x

Thank you for the question. 

The "admin.example.com" in the SOA line is the email address of the adminitsrator.  The "@ is used as an indication of the origin" in the DNS files and it cannot be used in the email address. In our configuration, if the DNS needed to inform the administratior of this domain something, it would translate "admin.example.com" to "admin@example.com" then send the email.

On page 6-18 we mention the control or data fields for the SOA record. More information is available in the RFC1035. 

fliker09

Oh, yes, indeed in 6.18 there is such info, thanks for pointing out! Does it matter the order of admin mail and primary name server?

Also, what does mean "if the DNS needed to inform the administratior of this domain something, it would translate "admin.example.com" to "admin@example.com" then send the email"? You mean a human being will do the translation and send email?

lee42x

Yes, the order is very important the DNS server code does the translation so it knows that the second field after the SOA identified is the email address and to make the character replacement of the first "." to be a "@" when the DNS sends the email.

fliker09

Thanks for explanation!

It seems that a correction is needed for 6.18 - Admin email is mentioned first. And may be mention the fact about the strict order?