DNS 2 SERVFAIL vs 6 YXDOMAIN
Both DNS 2 (SERVFAIL) and 6 (YXDOMAIN) belong to the DNS Response Codes (RCODEs) category. 2 indicates that server failure. The name server encountered an internal error while processing the query. Meanwhile, 6 means that name Exists when it should not. Used in dynamic updates to indicate a name that should not exist already has records.
説明
Server failure. The name server encountered an internal error while processing the query.
このコードが表示される場合
The recursive resolver could not get an authoritative answer — commonly caused by DNSSEC validation failures, unreachable upstream nameservers, or misconfigured zones.
解決方法
Try a different resolver (e.g., 8.8.8.8 or 1.1.1.1) to isolate the issue. If you control the zone, check DNSSEC signatures, SOA serial consistency, and nameserver reachability.
説明
Name Exists when it should not. Used in dynamic updates to indicate a name that should not exist already has records.
このコードが表示される場合
A DNS UPDATE prerequisite check failed because the domain name already exists when the update expected it to be absent.
解決方法
Review your dynamic update prerequisites. If you expect to create a new name, remove the existing records first or change the prerequisite to allow existing names.
主な違い
DNS 2: Server failure. The name server encountered an internal error while processing the query.
DNS 6: Name Exists when it should not. Used in dynamic updates to indicate a name that should not exist already has records.
You encounter 2 when the recursive resolver could not get an authoritative answer — commonly caused by DNSSEC validation failures, unreachable upstream nameservers, or misconfigured zones.
You encounter 6 when a DNS UPDATE prerequisite check failed because the domain name already exists when the update expected it to be absent.
どちらをいつ使うか
For 2 (SERVFAIL): Try a different resolver (e.g., 8.8.8.8 or 1.1.1.1) to isolate the issue. If you control the zone, check DNSSEC signatures, SOA serial consistency, and nameserver reachability. For 6 (YXDOMAIN): Review your dynamic update prerequisites. If you expect to create a new name, remove the existing records first or change the prerequisite to allow existing names.