The correct statements describing the differences between IPsec main mode and IPsec aggressive mode are:
A. The first packet of aggressive mode contains the peer ID, while the first packet of main mode does not.
In aggressive mode, the first packet contains identification information (such as the peer ID), whereas in main mode, the first packet does not contain such details, providing a higher level of security.
D. Six packets are usually exchanged during main mode, while only three packets are exchanged during aggressive mode.
Main mode typically involves the exchange of six packets to establish the IPsec tunnel, whereas aggressive mode streamlines the process with a reduced exchange of three packets.
The other statements (B and C) are not accurate:
B is incorrect because main mode can be used for dialup VPNs, and it is commonly used in such scenarios.
C is incorrect because both aggressive mode and main mode support Extended Authentication (XAuth), and XAuth is not exclusive to aggressive mode.