Anti-Replay Prevention in Cisco IOS IPsec Implementation

D.

In a Cisco IOS IPsec implementation, anti-replay prevention is used to prevent a potential attacker from capturing and replaying valid IPsec packets. The option used for anti-replay prevention in a Cisco IOS IPsec implementation is the sequence number.

The sequence number is a unique identifier that is assigned to each IPsec packet that is sent. This identifier is used by the receiver to detect and prevent replay attacks.

When a packet is sent, the sender increments the sequence number by one. The receiver checks the sequence number of the incoming packet and compares it with the previous sequence number. If the sequence number of the incoming packet is lower than or equal to the previous sequence number, the packet is considered a replay attack and is discarded.

Session tokens, one-time passwords, time stamps, and nonces are all used for different purposes in security protocols, but they are not used for anti-replay prevention in a Cisco IOS IPsec implementation.

• Session tokens are used to authenticate a user's session with a server, but they do not prevent replay attacks.
• One-time passwords are used to provide a temporary password that is used for authentication, but they do not prevent replay attacks.
• Time stamps are used to provide a timestamp for a message, but they do not prevent replay attacks.
• Nonces are used to provide a random number that is used for security protocols, but they do not prevent replay attacks.

Therefore, the correct option for anti-replay prevention in a Cisco IOS IPsec implementation is the sequence number.