I agree on Stefan, the correct lease time depends on a few parameters. How many users, how long the clients stay generally connected, what class network you have, how powerfull is your router. In my case many people walk in and out the clubhouse. At the most busiest times I see 100 simultanious connections. Every day I’m guessing that 700-1000 people will visit.
Our ISP provided a cheap home-use router that doesn’t support a good DHCP server with shorter lease times < 1 day so that whould mean a large DHCP pool with in turn the router can’t handle. The lease table would be too large to maintain next to the other functions the router has so the DORA functions fail and clients will asign themselves an APIPA address. Since the netwerk doesn’t contain a server of any kind I bought a cheap router (tp-link WR841n) that supports a good DHCP server with options to give clients, routing / DNS specification and shorter lease times.
I only enabled this router to act as dedicated DHCP server and gave clients a 30 minutes lease time. After the 30 minutes, the DHCP server will contact the client if it’s still there, if not it will release the IP-address if still present it will reassign 30 minutes to the client lease. Client will keep the same IP-address. DHCP range is set within the Private Address Range with 254 simultanious leases max. (bases on the total max. connections of the AP’s). This works great for my case.
Restarting a DHCP server and flushing its table is not a good idea, unless you make sure to disconnect all the clients from your network first (disable WiFi AP’s). Give it a minute at least to make sure all clients are disconnected. Then start up the network in the following order and wait until fully started and connected: router, DHCP server, Wifi Access Points.