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ProtocolCodes
21
DNS

21 BADALG

Algorithm not supported. The cryptographic algorithm specified in the TKEY or SIG record is not supported by the server.

On this page

When You See This Code

Your TKEY negotiation or DNSSEC operation requested an algorithm (e.g., HMAC-SHA512) that the server has not been compiled with or configured to accept.

How to Fix

Use a mutually supported algorithm. HMAC-SHA256 is widely supported for TSIG; for DNSSEC, check the server's supported algorithm list with its documentation.

Specification

View RFC / Specification →

Compare With

0 NOERROR 1 FORMERR 2 SERVFAIL 3 NXDOMAIN 4 NOTIMP 5 REFUSED 6 YXDOMAIN 7 YXRRSET 8 NXRRSET 9 NOTAUTH 10 NOTZONE 11 DSOTYPENI

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Glossary

TCP/IP Port Number Latency Timeout Firewall DNS over HTTPS (DoH) IPv6 Subnet (Subnetwork) MTU (Maximum Transmission Unit) UDP (User Datagram Protocol) DNS Lookup CDN (Content Delivery Network) Request-Response Model RFC (Request for Comments) IANA (Internet Assigned Numbers Authority) Wire Format Extension Mechanism Connectionless Text vs Binary Protocol DNS Resolution DNS Record Types TTL (Time to Live) DNSSEC (DNS Security Extensions) DNS over TLS (DoT) Anycast Recursive Resolver Authoritative Name Server Glue Record EDNS(0) DNS Zone DNS Propagation CNAME Record MX Record SRV Record PTR Record DNS Cache Poisoning DNS Root Server Split-Horizon DNS Wildcard DNS Record SPF, DKIM, and DMARC Email Deliverability MTA (Mail Transfer Agent) ARC (Authenticated Received Chain) BIMI (Brand Indicators for Message Identification) Service Discovery GSLB (Global Server Load Balancing) Failover Active-Passive HA

Frequently Asked Questions

What is DNS 21 BADALG?

Algorithm not supported. The cryptographic algorithm specified in the TKEY or SIG record is not supported by the server.

When do you see DNS 21 BADALG?

Your TKEY negotiation or DNSSEC operation requested an algorithm (e.g., HMAC-SHA512) that the server has not been compiled with or configured to accept.

How to fix DNS 21 BADALG?

Use a mutually supported algorithm. HMAC-SHA256 is widely supported for TSIG; for DNSSEC, check the server's supported algorithm list with its documentation.