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pioto
Asked: 2012-02-10 19:00:46 +0800 CST

Can I delegate part of a zone to another server?

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I guess I'm wondering something similar to Can I create DNS records for some hosts, delegate other queries in the same domain to another DNS server?, but I'm hoping I'll get a different answer with BIND.

Basically, I have home.mydomain.tld as a public A record already, that's dynamically updated. I'm wondering if there's some way to simply provide local service to that domain within my home network without overriding it. Really, just local AAAA records. The A records would hopefully come from my router's DNS/DHCP server; it isn't smart enough to know about IPv6 yet.

If not, I guess I can populate the A records semi-automatically every once in a while, but if it's possible to avoid doing that I'd like to try.

domain-name-system bind

2 Answers

  1. Of course you can. Any node in the namespace below the zone apex can be a delegation point.

    To clarify your question: To the rest of Internet you have, for example:

    ;; pioto.org. zone
@                   IN A 66.39.110.116
newpair             IN A 66.39.110.116
creandus            IN A 66.39.110.116

    But on your LAN, because you're so excited about all of these 1990s innovations and want to start experimenting with them, you want to have:

    ;; pioto.org. zone
@                   IN A 192.168.100.1
@                   IN AAAA FEC0:0100::1
newpair             IN A 192.168.100.2
newpair             IN AAAA FEC0:0100::2
_http._tcp          IN SRV 10 10 80 @
_http._tcp.newpair  IN SRV 10 10 80 newpair

    This is a simple exercise in split-horizon DNS service. Configure an internal content DNS server with the second set of data, and perform the prune-and-graft operation in the appropriate manner, using either stub zones with properly separate servers or views.

    Letting parts of the external DNS database be visible internally is — with properly separated content and proxy servers — a simple exercise in delegation on the content server:

    ;; pioto.org. zone, continued
creandus            IN NS NS1.PAIRNIC.COM.
creandus            IN NS NS2.PAIRNIC.COM.

    If you have a combined DHCP-plus-content-DNS service on your router, that knows about leased IP addresses and hostnames, or if you have Microsoft's DNS and DHCP servers on a Windows Server machine, then getting the IP addresses from the combined server is also an exercise in delegation:

    ;; pioto.org. zone, modified
newpair             IN NS a.ns.newpair ;; replaces the A and AAAA records
a.ns.newpair        IN A 192.168.1.1   ;; IP address of the DHCP+DNS server

    The only things that you cannot do are …

    • … use external data for pioto.org. itself. The zone apex cannot be delegated.
    • … retrieve A and AAAA resource records from different content DNS servers.

    Further reading

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  2. Best Answer

    It sounds like you have home.mydomain.tld as a public zone and you want to create internal records for PC.home.mydomain.tld, TV.home.mydomain.tld, refrigerator.home.mydomain.tld, etc.?

    About the only un-nasty way I can think of to do this without stepping on the home.mydomain.tld domain would be to create x.home.mydomain.tld and put everything under that zone, which is served by your local nameserver.

    You COULD create an individual zone for each of PC, TV, refrigerator, etc. above and have your local nameserver only be authoritative for those individual bits, but that means a huge number of one-entry zone files (YUCK!).

    Also note that any local zones you create would step on and override any outside DNS server's zones: It's not possible to have the A record for pc.home.mydomain.tld come from one NS and the AAAA record for it come from another: DNS delegates and declares authority by zone name, and that authority is for all record types within that zone.
    If a nameserver is told it is authoritative for something and can't find the record it will not forward the query up the DNS tree, it will simply return NXDOMAIN.

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