[dns-operations] NXDOMAIN and negative caching
mnsmitasin at lbl.gov
Mon Feb 1 23:21:47 UTC 2016
Just wanted to confirm my understanding:
- An NXDOMAIN / Name Error response indicates the domain name does not
exist, while a No Data response indicates the domain exists but no data
of the queried type exists. (Mostly looking at RFC 1035 Section 5.2.1)
- An NXDOMAIN should be cached for a given QNAME, QCLASS. (RFC 2038
What I infer from that (perhaps it's explicitly stated elsewhere?) is
- An NXDOMAIN indicates /no/ records exist for that name.
- When an NXDOMAIN is cached, it will be returned for /any/ QTYPE
matching the same QNAME, QCLASS.
We have a situation where an authoritative server (outside our control)
is returning a good A record but when the same name is queried for an NS
record, it returns NXDOMAIN. Once our caching nameservers get that
NXDOMAIN, they start returning it to our client queries for the A
record. If my understanding of the above is true, our caching
nameservers are behaving correctly, but the authoritative server should
not be returning NXDOMAIN for that name? If so, is anyone familiar with
the circumstances where that would be the case or have recommendations I
can forward on to the operators of that authoritative server?
LBLnet Services Group
Lawrence Berkeley National Laboratory
More information about the dns-operations