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The following the list of error messages that dnswalk will
return if it sees a potential problem with the database.
Duplicate messages will be suppressed automatically for each
zone.
X PTR Y: unknown host
X is a PTR record to Y, but Y is not a valid host (no A
record). These are often left over from when someone
deleted a host from the DNS and forgot to delete the
PTR record. These records should be removed.
X PTR Y: A record not found
X is a PTR record to Y, but the IP address associated
with the PTR record is not listed as an address for Y.
There should be an A record for every valid IP address
for a host. Many Internet services will not talk to
you if you have mismatched PTR records.
X PTR Y: CNAME (to Z)
X is a PTR record to Y, but Y is a CNAME to Z. PTR
records should point to the real name of a host, not an
alias.
X CNAME Y: unknown host
X is aliased to Y, but Y is not a valid host (no A
record). This is a stale entry and should be removed.
X CNAME Y: CNAME (to Z)
X is aliased to Y, but Y is aliased to Z. CNAMEs
should not be chained together. It has been known to
cause problems with some software.
X MX Y: unknown host
X is an MX to Y, but Y is not a valid host (no A
record). This is a stale entry and should be removed.
X MX Y: CNAME (to Z)
X is an MX to Y, but Y is an alias for Z. MX records
must point to the canonical name, not an alias.
X A Y: no PTR record
X has an IP address Y, but there is no PTR record to
map the IP address Y back to a hostname (usually X).
Many Internet servers (such as anonymous FTP servers)
will not talk to addresses that don't have PTR records.
warning: X has only one authoritative nameserver
Zones should have more than one authoritative name-
server, in case one is down or unreachable. Preferably
one should be off-site. Make sure the parent and child
nameservers list all authoritative nameservers for a
zone in the NS list.
X: invalid character(s) in name
Allowable characters in a domain name are the ASCII
letters a through Z the digits 0 through 9, and the "-"
character. A "." may be used only as a domain separa-
tor. Using non-standard characters can cause unexpected
software problems.
X: domain occurred twice, forgot trailing '.'?
A sanity check which looks for "dom.ain.dom.ain." in a
name. This is often caused by forgetting to put a
trailing '.' on the end of a name.
X A Y: points to Z
X has Y for an IP address, but the PTR record associ-
ated with Y returns "Z" as the name associated with
that host. This is not necessarily an error (for exam-
ple if you have an A record for your domain name), but
may be an indication of an A record which points to the
wrong host, or a PTR record that points to the wrong
host. You will get this error if you are trying to
alias one host to another with an A record. You should
use a CNAME instead.
X NS Y: lame NS delegation
Y is a listed nameserver for zone X, but Y is not
returning authoritative data for zone X. This is usu-
ally the result of a lack of communication on the part
of the respective hostmasters. Lame delegations are
not fatal problems except in severe cases, they just
tend to create significant increases in DNS traffic.
NS records for the parent and child domains should be
consistent, and each server listed in the NS record
MUST be able to answer with authoritative data, by
being explicitly configured as a primary or secondary
for the zone.
X NS Y: nameserver error (lame?)
These are any errors returned while contacting other
nameservers (like connection refused or timeout) This
could mean a lame delegation (the host is not running
a nameserver or is misconfigured), or simply that the
nameserver is temporarily unreachable.
Cannot check X: no available nameservers!
The X zone was delegated with NS records but all the
nameservers for the zone are either unavailable or say
that they have no data for the zone (are lame). Verify
that the X zone isn't a typo, and if not make sure that
all the listed nameservers are configured to answer
with data for the zone.
SEE ALSO
RFC 1034 - "DOMAIN NAMES - CONCEPTS AND FACILITIES"
RFC 1035 - "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION"
RFC 1123 - "Requirements for Internet Hosts -- Application and Support"
Paul Albitz, Cricket Liu: "DNS and BIND" O'Reilly & Associates.
RFC 1912 - "Common DNS Operational and Configuration Errors"
http://www.dns.net/dnsrd/ - DNS Resources Directory
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