If the user prefers to keep network activity alive while the endpoint is in sleep mode, Apple recommends setting **“Wake for network access” to Always. Otherwise, it is expected for DPD (Dead Peer Detection) to drop during sleep, assuming there are no network path issues.

Apple’s Behavior:

• "Wake for network access" (found in System Settings > Battery or Energy Saver > Power Adapter) enables a Mac to briefly wake from sleep when network activity occurs (e.g., for VPN keep alives, file sharing, or remote management).
• When set to "Always", the Mac will wake even during deep sleep (especially on power) to maintain network connections.
• When not enabled or set to something like "Only on Power Adapter", the system may go into full sleep and stop responding to network events — causing DPD (Dead Peer Detection) or other keep-alive mechanisms to fail.

We search for below tags on Apple support page; we will get the proof.

• Power Nap
• Wake-on-LAN
• VPN behavior during sleep
• Energy Saver settings