DNS 7 YXRRSET vs 18 BADTIME
Both DNS 7 (YXRRSET) and 18 (BADTIME) belong to the DNS Response Codes (RCODEs) category. 7 indicates that rR Set Exists when it should not. A resource record set exists that the update prerequisite says should not. Meanwhile, 18 means that signature out of time window. The TSIG signature timestamp is outside the allowed clock skew, indicating a time synchronization issue.
描述
RR Set Exists when it should not. A resource record set exists that the update prerequisite says should not.
何时出现
A DNS UPDATE failed because a specific RRset (e.g., an A record) already exists when the prerequisite required it to be absent.
如何修复
Delete the conflicting RRset before retrying the update, or adjust your prerequisite conditions to match the actual zone state.
描述
Signature out of time window. The TSIG signature timestamp is outside the allowed clock skew, indicating a time synchronization issue.
何时出现
The clocks on the DNS client and server are too far apart (usually more than 5 minutes), causing TSIG signature validation to fail.
如何修复
Synchronize clocks on both machines using NTP. Check that the TSIG fudge value (allowed skew) is reasonable — the default 300 seconds is usually sufficient.
主要区别
DNS 7: RR Set Exists when it should not. A resource record set exists that the update prerequisite says should not.
DNS 18: Signature out of time window. The TSIG signature timestamp is outside the allowed clock skew, indicating a time synchronization issue.
You encounter 7 when a DNS UPDATE failed because a specific RRset (e.g., an A record) already exists when the prerequisite required it to be absent.
You encounter 18 when the clocks on the DNS client and server are too far apart (usually more than 5 minutes), causing TSIG signature validation to fail.
何时使用哪个
For 7 (YXRRSET): Delete the conflicting RRset before retrying the update, or adjust your prerequisite conditions to match the actual zone state. For 18 (BADTIME): Synchronize clocks on both machines using NTP. Check that the TSIG fudge value (allowed skew) is reasonable — the default 300 seconds is usually sufficient.