What must be true about switches for them to exchange VTP messages?

For switches to exchange VLAN Trunking Protocol (VTP) messages, it is essential that they share the same VTP version and domain name. VTP is a Cisco proprietary protocol used to manage VLANs across multiple switches in a network. The VTP domain name acts as a unique identifier that allows switches to identify the network they belong to and ensures that they can communicate VTP advertisements appropriately.

If the switches are not part of the same VTP domain, they will not process VTP messages sent by one another, even if they are connected and within the same broadcast domain. Ensuring that all participating switches use the same VTP version is also critical because different versions may implement features and commands differently, leading to incompatibility in the VTP messages they exchange. This coordination is necessary for effective VLAN management across the network.

The other options do not impact VTP message exchange directly. For instance, the number of ports on the switches or having identical configurations regarding IP addresses is not required for VTP operation. Thus, sharing the same VTP version and domain name is the fundamental requirement for VTP message exchange between switches.