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I'm searching for a way for a placeholder in my bind zone files. I found some information on the NULL RR which would be perfect, but wikipedia states it's obsolete by RFC 883. I read through this RFC but could not find any reference for this statement.

Is the NULL RR obsolete or not? Is it acceptable to use it as placeholder?

At the moment I use this:

somename                   IN TXT     "placeholder"
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What are you actually trying to accomplish? –  womble Apr 8 '12 at 7:45
    
I want a placeholder to add some names for later use, not forget them and keep my files better structured. –  Mose Apr 8 '12 at 8:07
    
Comments will work perfectly well for what you want to achieve. –  womble Apr 8 '12 at 8:30
    
You're right. Didn't see the forest for the trees :-) But besides this just for the record: Is NULL obsolete or not? –  Mose Apr 8 '12 at 9:15

2 Answers 2

up vote 1 down vote accepted

Comments will work just fine for keeping a note of future allocations in a zone file (this doesn't work quite so well if you're using a non-file method of storage, like PoserDNS with a database backend, but in that case you should have all sorts of automated systems that take care of that sort of thing for you).

As far as the NULL RDATA type, it's marked as "EXPERIMENTAL" in RFC1035, and none of the RFCs listed as updates seem to cover it (at least, based on a 2-second glance at their titles). So I can't say for sure if it's obsolete or not, but I certainly wouldn't be relying on it for anything.

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Some tools (like 'dig') report parse errors when encountering NULL records - presumably this means having them in your zone at all is a bad idea, as an ANY query for one of your reserved names would return them. My advice is to just don't use NULL RRs. –  Habbie Apr 8 '12 at 17:49

The IANA list of registered DNS parameters still lists it as EXPERIMENTAL.

This is as close to an authoritative list of record types as you can get.

Note however that RFC 1035 also says this:

NULL RRs are not allowed in master files

So essentially it's saying that NULL records may exist on the wire, but cannot be part of a zone file.

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