Which IPsec mode includes peer ID information in the first packet?

Aggressive mode in IPsec is designed to establish secure connections quickly compared to other modes. One of its defining features is that it includes peer ID information in the first packet exchanged between the two peers. This allows for a faster setup of the secure channel because the initiating party can send its identity along with its first message, which can reduce the number of exchanges required to complete the authentication process.

Unlike Main mode, which involves a more extended exchange that separates identity from the key information, Aggressive mode allows the communication to take place in fewer steps. Quick mode is focused on renegotiating the security parameters of existing connections after a secure tunnel has been established, which does not involve sending peer ID in the initial packet. Phase 2 mode typically refers to the second phase of the IPsec process, which deals with establishing the secure tunnel after the initial negotiations, and does not involve initial packet exchanges like Aggressive mode does.

The inclusion of peer ID information in the first packet is a crucial component of how Aggressive mode optimizes the process of establishing VPN connections, making it a practical option in scenarios where speed is prioritized.