The security appliance in the network XXXX was unable to issue an IP address to new clients on subnet 10.11.1.0/24'10.11.1.1 because it has exhausted its pool of DHCP leases. New clients will not be able to connect to the network until this issue is resolved (e.g. by increasing the size of the subnet). I received this message since I would like to delete clients who are no longer there to recover their ip addresses Can someone help me please?
Depending on how urgent it is and if you are able to reboot clients and/or your MX I would suggest just making the DHCP lease time shorter like 1 hour. If you have significantly more clients that need to connect, you can also do as it suggests and open up your subnet to /23 or /22 to allow more clients on that subnet. Consider what other implication of allowing more clients are too though. Maybe you don't want 1000 guest clients on your network at once, for example.
If you have a network i.e. guest wifi where client devices come and go in quick succession a shorter lease time is a much better option. This is also in the case of client devices that use virtual MAC to increase security.
@sj093, there is no way to manually delete a lease in the MX DHCP server. The lease will be removed, and thus the IP address made available for another system, when it expires.
As others have said, your two options are to use shorter lease times, or a bigger subnet. If the systems attaching to this network are changing regularly then you want to shorten your lease time. If it’s that you have a large number of clients connected then you could move to a /23 subnet, or consider whether you should be introducing another VLAN/subnet.