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A domain (abc.net) publishes a site on rental server A.
Only the subdomain (a.abc.net) wants to publish the site on the rental server B.
The DNS record was set as follows.

Host name Type Content
a.abc.net A IP address (rental server B)

After examining it, it is necessary to set the sub-domain name server (rental server B name server) in the zone information in addition to the above settings, so why should I set B name server? I didn't know what to do. If it is set, will it look like the following?

Host name Type Content
a.abc.net NS Name server (rental server B)

A.abc.net is not enough for a single record of "IP address (rental server B)". Is there anyone who can explain why, including why?

  • Answer # 1

    I don't know if I can explain it well.

    If only A record is registered,
    When resolving names from the root,
    Since it can be solved with A record of the upper zone,
    I have to guide where the NS of "a.abc.net" is.
    I don't think you can reach it.

    How about it?
    Have you boiled the image?

    ☆ postscript @ 8.28

    Using a specific example, I will explain "a little more in detail about the part that can be resolved with the A record in the upper zone".

    If you register the following content only as an A record for the domain (abc.net):
    ・ A.abc.net (A record): 11.22.33.44
    At this point, the registered value (11.22.33.44) is returned, so there is no problem.
    When this changes,
    To register a value of 99.88.77.66 for the FQDN "a.abc.net"
    What will happen?

    Since "a.abc.net" is created and managed as a subdomain,
    I would like to change this value.
    However, if the value of the domain (abc.net) remains unchanged
    The expected value is not returned.

    To solve this, it is necessary to guide where the NS of "a.abc.net" is.

    ☆ postscript @ 8.29

    >From what happens when "this is changed",
    ⇒ Including two cases, NS is registered and this is not the case
    I would like to present it with reference to the flow I wrote.

    1. When only A record is registered
    ①. Perform name resolution for "http://a.abc.net".
    ②. Inquire the root DNS server "." ⇨ "Tell me the IP address of" a.abc.net "!"
    Answer ⇨ "Ask the 'net' DNS server"
    ③. Inquiry to "net" DNS server ⇨ "Tell me the IP address of" a.abc.net "!"
    Answer ⇨ "Ask DNS server of" abc.net ""
    ④. Ask "abc.net" DNS server (rental server A DNS server) ⇨ "Tell me the IP address of" a.abc.net "!"
    Answer ⇨ "The IP address is 11.22.33.44"

    ⇒ In this case, I think that it is not inconvenient as a behavior that can be seen by the user.

    Next,
    2. When A record and NS record are registered
    ①. Perform name resolution for "http://a.abc.net".
    ②. Contact root DNS server "." ⇨ "Tell me the IP address of" a.abc.net "!"
    Answer ⇨ "Ask the 'net' DNS server"
    ③. Contact "net" DNS server ⇨ "Tell me the IP address of" a.abc.net "!"
    Answer ⇨ "Ask DNS server of" abc.net ""
    ④. Ask abc.net DNS server (rental server A DNS server) ⇨
    Answer ⇨ "'a.abc.net' is registered as a subdomain, so ask the NS record name server"
    ⑤. Inquire NS server of "a.abc.net" ⇨
    Answer ⇨ "The IP address is 11.22.33.44"

    ⇒In this case, the inquiry step increases by one, but the returned value is the same.
    However, considering maintenance, it is necessary to change the IP address of "a.abc.net"
    Suppose that you want to change to "99.88.77.66".

    At that time and behavior again in the case of 2 cases, it will be as follows.

    1. When only A record is registered
    ① ~ ③ : Omitted
    ④. Ask "abc.net" DNS server (rental server A DNS server) ⇨ "Tell me the IP address of" a.abc.net "!"
    Answer ⇨ "The IP address is 11.22.33.44"

    ⇒ At this point, the problem is that the old domain's A record is an old IP
    Since "11.22.33.44" is returned, it is not the intended behavior.

    In contrast,
    2. When A record and NS record are registered
    ① ~ ④ : Omitted
    ⑤. Inquire NS server of "a.abc.net" ⇨
    Answer ⇨ "The IP address is" 99.88.77.66 ""

    ⇒The IP address you intended is returned.

    In short, creating a subdomain instead of one of the top records
    There seems to be a reason to manage them individually.
    Independence at that time is realized for the above reasons.

    ☆ Addition @ 8.30

    >When "Rental Server B's IP address" is changed, is it necessary to set a name server so that it can be recognized correctly?

    ⇒I think we meet with that recognition.

    >Because NS record is set, the IP address is NS record destination rental server B
    Can you tell me ...?
    Then A record is unnecessary? ? Or is it necessary for some reason?

    ⇒That's right, I'm sorry for a little regret, but I don't need an A record for the higher domain.
    It may be set in some special cases. . .

  • Answer # 2

    [Domain settings] Content written for using a domain acquired and managed by another company
    "Set your own domain" and "Set your own domain subdomain (use Sakura's name server)" can be understood without problems, "Set your own domain's subdomain (use other company's name server)" So you don't know if this step is necessary?


    [Domain settings] "Prerequisites" are written in the contents written to use a domain acquired and managed by another company.

    There is a precondition that "This manual explains how to use the Sakura Internet name server.". It is set to transfer the authority of the domain name server to the name server on the Sakura Internet.

    In other words, the contents described in this manual are that the domain (main part) remains in the name server of the other company, and only the subdomain is `` Sakura Internet rental using the Sakura Internet name server. Use the server.


    If you don't use the Sakura Internet name server, change it to the name server you originally used

    sub.example.com A Sakura Rental Server IP address


    Just add A record, you can use without problems. (Used.)