What do the clients think their lease time is?

Was the lease time previously set to longer?

Lease time doesn't mean that after that time the same device will get a new/different ip, maybe you are expecting a behavior that shouldn't happen?

You are probably right.
But shouldn't a device that is turned off get a new IP after it's back on?

Based on experience/personal observation only, the opposite is the case usually with home equipment.
You go on vacation for a week and when you're back your phone gets the same ip as soon as it connects to the home router 😉 The same that it has been getting for the last year maybe.
Again, not always and not necessarily, but I'd say it's common. I don't know if there's something in home routers that says "prefer assigning same ip for known devices" but it seems it's happening as long as your network doesn't change/have new devices introduced.

konc wrote on 2020-12-23, 22:25:

I don't know if there's something in home routers that says "prefer assigning same ip for known devices" but it seems it's happening as long as your network doesn't change/have new devices introduced.

There is a feature on this ONT that says "Add reserved address" in the DHCP menu. Right now it's empty but it still reserves certain IPs to certain devices.
It's not too important so I don't really care, it just makes the whole IP leasing pointless. My address range is ....7-251 so it would take a LOT of time to run out of available leases. And yes, lease time was set to 24 hours before.

Miphee wrote on 2020-12-23, 21:28:

You are probably right.
But shouldn't a device that is turned off get a new IP after it's back on?

Not always. The router might recognice the devices unique mac address and match it to the same ip the device had prior.

Okay, thanks,
One more question: what is the practical use of address leasing?
Is it only useful in a corporate setting with thousands of clients?

Or with a place where most users are temporary users, like restaurants, stores with indoor WiFi, campings, hotels etc. Also, without a lease, a client would never ask for a new IP again so *if* you would want to assign an IP to a different device it would be impossible because anytime you switch the old device back on, it would create an address conflict. You would have to manually reconfigure the old device first. That is a lot of hassle, that is why using IP leases is very convenient, even if you assign fixed IPs to your devices (or your router does it for you)

Miphee wrote on 2020-12-24, 08:01:

Okay, thanks,
One more question: what is the practical use of address leasing?
Is it only useful in a corporate setting with thousands of clients?

It's mostly for the release part, to ensure that you'll have available ips in crowded environments, or as digistorm said it more correctly in environments with many temporary users
And less to have a device keeping the same ip for long, this can be achieved by binding an ip to a specific MAC.
Imagine a coffee shop for example, it'll run out of ips in a couple of hours if lease time is not configured properly. But yes, for home use it doesn't really matter.

Miphee wrote on 2020-12-23, 23:34:

And yes, lease time was set to 24 hours before.

So the clients have existing leases and just aren't asking your DHCP server for new ones until they expire. And yes, when they do the DHCP server will probably offer the client the same IP address for stability.

I have no idea why your DHCP server interface shows clients who have no lease as negative time, but appearances aside nothing is going wrong here.

Also another advantage of shorter leases I don't see mentioned: effecting changes more quickly.

Say you want to move a device from one IP address to another, you can just change that in the DHCP server. If the lease time is 3 days, that will take 3 days to take effect. If the lease time is 1 hour, it will take 1 hour.

A disadvantage of shorter leases is that it creates more network noise.

I don't think lease time is likely to matter in any way on a home network.

Thanks for clearing that all up!