1 The following the list of error messages that dnswalk will 2 return if it sees a potential problem with the database. 3 Duplicate messages will be suppressed automatically for each 4 zone. 5 X PTR Y: unknown host 6 X is a PTR record to Y, but Y is not a valid host (no A 7 record). These are often left over from when someone 8 deleted a host from the DNS and forgot to delete the 9 PTR record. These records should be removed. 10 X PTR Y: A record not found 11 X is a PTR record to Y, but the IP address associated 12 with the PTR record is not listed as an address for Y. 13 There should be an A record for every valid IP address 14 for a host. Many Internet services will not talk to 15 you if you have mismatched PTR records. 16 X PTR Y: CNAME (to Z) 17 X is a PTR record to Y, but Y is a CNAME to Z. PTR 18 records should point to the real name of a host, not an 19 alias. 20 X CNAME Y: unknown host 21 X is aliased to Y, but Y is not a valid host (no A 22 record). This is a stale entry and should be removed. 23 X CNAME Y: CNAME (to Z) 24 X is aliased to Y, but Y is aliased to Z. CNAMEs 25 should not be chained together. It has been known to 26 cause problems with some software. 27 X MX Y: unknown host 28 X is an MX to Y, but Y is not a valid host (no A 29 record). This is a stale entry and should be removed. 30 X MX Y: CNAME (to Z) 31 X is an MX to Y, but Y is an alias for Z. MX records 32 must point to the canonical name, not an alias. 33 X A Y: no PTR record 34 X has an IP address Y, but there is no PTR record to 35 map the IP address Y back to a hostname (usually X). 36 Many Internet servers (such as anonymous FTP servers) 37 will not talk to addresses that don't have PTR records. 38 warning: X has only one authoritative nameserver 39 Zones should have more than one authoritative name- 40 server, in case one is down or unreachable. Preferably 41 one should be off-site. Make sure the parent and child 42 nameservers list all authoritative nameservers for a 43 zone in the NS list. 44 X: invalid character(s) in name 45 Allowable characters in a domain name are the ASCII 46 letters a through Z the digits 0 through 9, and the "-" 47 character. A "." may be used only as a domain separa- 48 tor. Using non-standard characters can cause unexpected 49 software problems. 50 X: domain occurred twice, forgot trailing '.'? 51 A sanity check which looks for "dom.ain.dom.ain." in a 52 name. This is often caused by forgetting to put a 53 trailing '.' on the end of a name. 54 X A Y: points to Z 55 X has Y for an IP address, but the PTR record associ- 56 ated with Y returns "Z" as the name associated with 57 that host. This is not necessarily an error (for exam- 58 ple if you have an A record for your domain name), but 59 may be an indication of an A record which points to the 60 wrong host, or a PTR record that points to the wrong 61 host. You will get this error if you are trying to 62 alias one host to another with an A record. You should 63 use a CNAME instead. 64 X NS Y: lame NS delegation 65 Y is a listed nameserver for zone X, but Y is not 66 returning authoritative data for zone X. This is usu- 67 ally the result of a lack of communication on the part 68 of the respective hostmasters. Lame delegations are 69 not fatal problems except in severe cases, they just 70 tend to create significant increases in DNS traffic. 71 NS records for the parent and child domains should be 72 consistent, and each server listed in the NS record 73 MUST be able to answer with authoritative data, by 74 being explicitly configured as a primary or secondary 75 for the zone. 76 X NS Y: nameserver error (lame?) 77 These are any errors returned while contacting other 78 nameservers (like connection refused or timeout) This 79 could mean a lame delegation (the host is not running 80 a nameserver or is misconfigured), or simply that the 81 nameserver is temporarily unreachable. 82 Cannot check X: no available nameservers! 83 The X zone was delegated with NS records but all the 84 nameservers for the zone are either unavailable or say 85 that they have no data for the zone (are lame). Verify 86 that the X zone isn't a typo, and if not make sure that 87 all the listed nameservers are configured to answer 88 with data for the zone. 89 90SEE ALSO 91 RFC 1034 - "DOMAIN NAMES - CONCEPTS AND FACILITIES" 92 RFC 1035 - "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION" 93 RFC 1123 - "Requirements for Internet Hosts -- Application and Support" 94 Paul Albitz, Cricket Liu: "DNS and BIND" O'Reilly & Associates. 95 RFC 1912 - "Common DNS Operational and Configuration Errors" 96 http://www.dns.net/dnsrd/ - DNS Resources Directory 97