Konica Minolta IEEE 802.1X Error 21
The server certificate did not match the server identity that the printer is configured to verify.
Error meaning
Server-ID verification of the EAP server certificate failed.
This meaning is tied to the reviewed family/platform and subsystem below; do not reuse the number or wording by itself on a different printer family or protocol.
Applies to
bizhub C287/C227
- bizhub C287
- bizhub C227
Common formatting
These are formatting/lookup aliases for this reviewed condition, not separate error pages.
- 21
- ieee8021x-21
What usually causes it
- The expected RADIUS server name/ID in the printer no longer matches the certificate presented by the server.
- A certificate renewal changed the subject or subject-alternative name without updating the printer's verification setting.
- The printer reached a different authentication server whose certificate uses another valid identity.
What to try
Record the expected server ID configured on the printer
Do not change it yet; first capture the name or identifier the C287/C227 is trying to verify.
Compare that value with the current RADIUS certificate
Have the administrator check the certificate subject and subject-alternative names presented to this printer.
Check for server or load-balancer changes
A new RADIUS node or certificate can create a name mismatch even when the CA chain is trusted.
Correct the identity match and retry
Update the intended server identity or certificate deployment so the names agree, then reconnect with verification still enabled.
After each corrective action
Retry the same operation that produced 21. If it now works, stop there rather than changing unrelated printer, network, supply, or service settings.
If the code returns
If code 21 continues after the expected name matches the certificate, verify which RADIUS node actually handled the request and whether all nodes use the same certificate identity.
When service may be needed
This condition belongs to secure server-identity verification. It should be corrected by the network/security administrator, not bypassed and not treated as a mechanical printer repair.
Continue with guided troubleshooting
If the printer still is not working after the reviewed checks, carry this verified error context into the guided troubleshooter.
Related information
Verified source
Official Konica Minolta product-family user guide. Candidate meanings are paraphrased from protocol-specific code tables; manufacturer prose must not be copied into public pages.