DNS
16 BADVERS/BADSIG
Bad OPT Version or TSIG Signature Failure. Either the EDNS version in the OPT record is not supported, or the TSIG signature on the message failed verification.
When You See This Code
As BADVERS: your client sent an EDNS version higher than the server supports. As BADSIG: the TSIG MAC on the message did not match, indicating a shared-secret mismatch or message tampering.
How to Fix
For BADVERS, downgrade the EDNS version (most servers support version 0 only). For BADSIG, regenerate and re-synchronize the TSIG shared secret on both endpoints.