The following message appears after the debug eigrp packets command has been enabled: EIGRP: Fa0/0: ignored packet from 10.1.12.2, opcode = 5 (invalid authentication) What would cause this message to appear?

Last Updated: Jun 29, 2026
IT Exam Items Repository › Category: CCNP ENARSI v9 › The following message appears after the debug eigrp packets command has been enabled: EIGRP: Fa0/0: ignored packet from 10.1.12.2, opcode = 5 (invalid authentication) What would cause this message to appear?

The following message appears after the debug eigrp packets command has been enabled: EIGRP: Fa0/0: ignored packet from 10.1.12.2, opcode = 5 (invalid authentication) What would cause this message to appear?

  • The network mask on interface F0/0 does not match between the EIGRP neighbors.
  • The authentication type does not match between the EIGRP neighbors.
  • The AS number does not match between the EIGRP neighbors.
  • The authentication key or string does not match between the EIGRP neighbors.

Explanation: In EIGRP packet debugging, the message "(invalid authentication)" specifically indicates that while authentication is configured on both sides, there is a mismatch in the key ID or the key string (password) being used.

Related exam: Checkpoint Exam: Layer 3 Technologies – EIGRP

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