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How can Windows "see" information of an ethernet adapter's lease (like lease obtained/expires), when that lease comes from the ISP, but when there's a router in between?

I've assumed that lease information on a LAN machine would be purely internal to the LAN, assigned and managed by the router, according to either DHCP or static lease times.

For reference, I've assumed it's the ISP lease because the machine's lease is continuously resetting to an expiration of just a few minutes in the future, at which point the ISP modem goes down.

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I feel like you are having a larger problem and are not asking the right question...are you having disconnection issues? – horatio May 9 '13 at 14:31
up vote 3 down vote accepted

If your PC is getting its address from the router than it's the lease time from the router.

With DHCP leases the address will try to be "re-leased" at half the time. For instance if your computer leases an IP addess and the lease is 4 days, at the 2 day mark the software will try to lease the IP address again.

This can be a benefit if you don't have the DHCP on the local network. You would set the lease time low like 24 hours. That way your system would try and lease the same address at 12 hours in case access to the dhcp server is interrupted. That way you will still have an IP address while giving time to get the server back online.

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The only possibility for an internal LAN machine could see an external DHCP is through the use of some sort of forwarding or relay on the router (modem).

The LAN machine should be getting an IP address from the router, if configured that way, and within the DHCPOFFER phase of the connection is where the options (lease) come in play.

Given the information I would suspect that is an issue with the router.

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