Another reason that can prevent the devices from connecting to the server is the DHCP lease time. In this case, if a device is idle for an extended amount of time, the network will un-assign the IP address from the device causing it to become unreachable. This configuration is common in networks in order to ensure IPs are available for active devices.
DHCP is an extremely common configuration for networks in which a large number of devices are usually connected to. When configured, it drops devices that are not in use, to make room for the devices that are in use, being a very popular optimization strategy for enterprise networks.
Once the DHCP lease expires, any devices that are not in use will lose valid internet connection and will not be able to be reached by the MDM server. One way to verify if the DHCP lease time is interrupting the connection between the MDM Solution and the device is to send a command to the device and check the last update you receive from the MDM (Update Info).
A common troubleshooting step to is to restart the device. When doing that, you are basically renewing your connection with the DHCP and for this reason the device may receive and act upon all the pending commands.
However, it’s nice to have in mind that if a device holds an IP for too much time, when there’s a new device, an IP address may not be available for this specific device (because there would be no IP range available). On the other hand, if this time is too short, the device can lose its connection and will not be reachable.
With that in mind, our suggestion is to configure a subnet mask in a way that current and future devices can be accounted for. A majority of organizations use /24 (254 hosts/not), but this amount must be calculated based on the number of devices in your organization.