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I've been trying to figure out how to set up a reverse zone based on an already existing forward zone, but I keep getting an error saying server can't find xx.xxx.xx.xxx.in-addr.arpa: SERVFAIL whenever I try to run an IP through nslookup. Here's the forward zone in question:

$TTL    15M
@       IN      SOA     ns1.b900.et. root.b900.et. (
                     2019061200         ; Serial
                            15M         ; Refresh
                             5M         ; Retry
                           120M         ; Expire
                            600 )       ; Negative Cache TTL
@              IN      NS      ns1
@              IN      A       164.40.155.48
ns1            IN      A       164.40.155.48
b900           IN      A       164.40.155.48

And here's the reverse zone:

$ORIGIN 42.168.192.in-addr.arpa.
$TTL    15M
@       IN      SOA     ns1.b900.et. root.b900.et. (
                     2019061201         ; Serial
                            15M         ; Refresh
                             5M         ; Retry
                           120M         ; Expire
                            600 )       ; Negative Cache TTL
@       IN      NS      ns1.b900.et.  
48      IN      PTR     ns1.b900.et.

Running named-checkzone doesn't return anything, so I'm wondering what I'm doing wrong.

  • 1
    I don’t know whether it’s a general rule, but I find it’s common that reverse DNS is managed by whoever owns “your” IP range. – Mikael H Jun 12 at 10:07
  • @MikaelH true, but here the IP addresses are in the private block of 192.168.0.0/16 (rfc1918 section 3 and rfc6761 section 6.1), so anyone is free to (locally) manage the reverse handling. – Patrick Mevzek Jun 12 at 15:51
  • "what I'm doing wrong. " in all cases like that you need to show exactly what you tried, what command you entered. You have shown only part of the response, and redacted. Show real commands and outputs. – Patrick Mevzek Jun 12 at 15:52
  • Your reverse zone (192.168.42.0/24) does not match at all your forward zone, which references 164.40.155.48. So your question is really not clear. – Patrick Mevzek Jun 12 at 15:53
  • @PatrickMevzek: Correct; I missed that the reverse zone pertained to local addresses. With split DNS there’s nothing preventing you from having a reverse zonefile for internal use, naturally. – Mikael H Jun 12 at 16:31
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The reverse lookup zone is managed by the entity that manages that particular netblock, which almost certainly isn't you.

  • Except that this block (192.168.0.0/16) is private, hence there is no specific entity managing it (except IANA if you want) – Patrick Mevzek Jun 12 at 15:52
  • True enough. I didn't pay enough attention to the zone in the question. – joeqwerty Jun 12 at 21:02

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