SYSTEM ADMINISTRATION COMPREHENSIVE
REVIEW QUESTIONS AND CORRECT
ANSWERS 2026
▶ Error: CRYPTO-6-IKMP_SA_NOTFOUND: IKE message from x.x.x.x
failed its sanity check or is malformed.
What is the most likely cause of this error?
A) Incorrect access control lists (ACLs)
B) High CPU utilization on the peer router
C) Outdated firmware on one of the devices
D) Mismatch in Phase 1 parameters like encryption algorithms. Answer:
Correct Answer: D) Mismatch in Phase 1 parameters like encryption
algorithms
▶ Error: CRYPTO-6-IKMP_NO_CERT: No certificate found for the peer
x.x.x.x.
What is the most likely cause of this error?
A) The certificate on the peer device has expired
B) Incorrect pre-shared keys
C) Network interface is down
D) Incompatible Diffie-Hellman group. Answer: Correct Answer: A) The
certificate on the peer device has expired
▶ Error: CRYPTO-4-IKMP_NO_PEER_CERT: Received a certificate from
x.x.x.x which is not trusted.
What is the most likely cause of this error?
A) Inconsistent routing paths
B) Mismatched encryption algorithms
C) The peer's certificate authority (CA) is not trusted
D) Incorrect firewall rules blocking IKE traffic. Answer: Correct Answer: C)
The peer's certificate authority (CA) is not trusted
, ▶ Error: CRYPTO-4-IKMP_INVALID_EXCH_TYPE: Invalid exchange type
243 from x.x.x.x.
What is the most likely cause of this error?
A) Incorrect PSKs
B) Unsupported or mismatched IKE version
C) The peer device is down
D) Certificate chain is incomplete. Answer: Correct Answer: B)
Unsupported or mismatched IKE version
▶ Error: CRYPTO-4-IKMP_MODE_FAILURE: Processing of Quick mode
failed with peer at x.x.x.x.
What is the most likely cause of this error?
A) Network interface issues
B) Expired certificates
C) Mismatched transform sets or ACLs
D) Routing loops detected. Answer: Correct Answer: C) Mismatched
transform sets or ACLs
▶ Error: CRYPTO-4-IKMP_RETRANS_TIMER: Peer x.x.x.x is not
responding. Retransmission retry count reached.
What is the most likely cause of this error?
A) Incorrect firewall rules
B) Network connectivity issues or peer device is down
C) Mismatched Phase 2 parameters
D) Unsupported encryption algorithm. Answer: Correct Answer: B)
Network connectivity issues or peer device is down
▶ Error: CRYPTO-6-IKMP_NAT_DETECTED: NAT is detected between
x.x.x.x and x.x.x.x.
What is the most likely cause of this error?
A) Incorrectly configured transform sets
B) Routing issues between peers
C) Mismatched PSKs
D) NAT is present and NAT-T is not configured. Answer: Correct Answer:
D) NAT is present and NAT-T is not configured
REVIEW QUESTIONS AND CORRECT
ANSWERS 2026
▶ Error: CRYPTO-6-IKMP_SA_NOTFOUND: IKE message from x.x.x.x
failed its sanity check or is malformed.
What is the most likely cause of this error?
A) Incorrect access control lists (ACLs)
B) High CPU utilization on the peer router
C) Outdated firmware on one of the devices
D) Mismatch in Phase 1 parameters like encryption algorithms. Answer:
Correct Answer: D) Mismatch in Phase 1 parameters like encryption
algorithms
▶ Error: CRYPTO-6-IKMP_NO_CERT: No certificate found for the peer
x.x.x.x.
What is the most likely cause of this error?
A) The certificate on the peer device has expired
B) Incorrect pre-shared keys
C) Network interface is down
D) Incompatible Diffie-Hellman group. Answer: Correct Answer: A) The
certificate on the peer device has expired
▶ Error: CRYPTO-4-IKMP_NO_PEER_CERT: Received a certificate from
x.x.x.x which is not trusted.
What is the most likely cause of this error?
A) Inconsistent routing paths
B) Mismatched encryption algorithms
C) The peer's certificate authority (CA) is not trusted
D) Incorrect firewall rules blocking IKE traffic. Answer: Correct Answer: C)
The peer's certificate authority (CA) is not trusted
, ▶ Error: CRYPTO-4-IKMP_INVALID_EXCH_TYPE: Invalid exchange type
243 from x.x.x.x.
What is the most likely cause of this error?
A) Incorrect PSKs
B) Unsupported or mismatched IKE version
C) The peer device is down
D) Certificate chain is incomplete. Answer: Correct Answer: B)
Unsupported or mismatched IKE version
▶ Error: CRYPTO-4-IKMP_MODE_FAILURE: Processing of Quick mode
failed with peer at x.x.x.x.
What is the most likely cause of this error?
A) Network interface issues
B) Expired certificates
C) Mismatched transform sets or ACLs
D) Routing loops detected. Answer: Correct Answer: C) Mismatched
transform sets or ACLs
▶ Error: CRYPTO-4-IKMP_RETRANS_TIMER: Peer x.x.x.x is not
responding. Retransmission retry count reached.
What is the most likely cause of this error?
A) Incorrect firewall rules
B) Network connectivity issues or peer device is down
C) Mismatched Phase 2 parameters
D) Unsupported encryption algorithm. Answer: Correct Answer: B)
Network connectivity issues or peer device is down
▶ Error: CRYPTO-6-IKMP_NAT_DETECTED: NAT is detected between
x.x.x.x and x.x.x.x.
What is the most likely cause of this error?
A) Incorrectly configured transform sets
B) Routing issues between peers
C) Mismatched PSKs
D) NAT is present and NAT-T is not configured. Answer: Correct Answer:
D) NAT is present and NAT-T is not configured
