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=============================================================================== Robb Kambic Unidata Program Center Software Engineer III Univ. Corp for Atmospheric Research address@hidden WWW: http://www.unidata.ucar.edu/ =============================================================================== ---------- Forwarded message ---------- Date: Wed, 6 Sep 2000 14:46:48 -0600 (MDT) From: Greg Woods <address@hidden> To: address@hidden Subject: DNS status The upgrade of the DNS servers on ncar, phoenix, fl-phx, and bubby has been largely successful. The named crashes have stopped. One difference between the old and new versions that has bit us is even stricter enforcement of DNS rules. In particular, if a name is found that has both a CNAME and other records, the entire zone will not load. This has never been legal but the old DNS server would simply log a warning. The new version refuses to load the zone at all. There is supposed to be a "check-names" option for the new version that will either ignore this check or only log warnings, but I cannot get this to work. The external DNS server on ncar still refuses to load the ucar.edu zone if there is a "CNAME and other data" error. Therefore, I have modified the dns_update script that updates the external DNS server from the data in the divisional subdomain servers to check for this. The divisional subzone will not be updated if one of these errors is found. Therefore, if you are one of the divisions that I have already notified of this type of error, your DNS updates *will not propogate* outside of UCAR until the problem is fixed. I am sorry to have to do this but the alternative is that the entire ucar.edu zone won't propogate when this occurs. To be specific: what is not allowed is to have a name on the LEFT HAND SIDE of a CNAME record, which also appears on the LEFT HAND SIDE of any other record. If a name appears on the LHS of a CNAME, it cannot appear on the LHS anywhere else in your zone. You can't have a CNAME and also an MX for the same name (the most common error I have seen). It *is* legal to have a CNAME and an MX *pointing* to the same name (on the RHS of the record). Example 1: This is not legal www in cname server www in mx 10 server (In example 1, the MX record is superfluous) Example 2: This is legal www in cname server mailhost in mx 10 server Example 3: This is legal but not recommended www in cname mailhost mailhost in cname server (Some large sites, e.g. aol.com, use this kind of setup to do load balancing between mail servers, but the DNS spec says that CNAMEs should not point to other CNAMEs. This is not currently enforced by default. In the above example, just make the www cname point directly to server). The divisions that currently have "CNAME and other data" errors are MMM and CGD. Your zones will not update in the external server until these errors are corrected. --Greg