A. When a RAS server is set to allocate IP addresses from DHCP, it grabs n+1 addresses when the service starts, (where n is the number of dial-up interfaces), and keeps them. Therefore, the lease time is largely irrelevant. When a client dials in, the RAS server issues one of these cached leases and the RAS server maintains the lease on behalf of the client. The RAS server only records the address of the DHCP server and the lease parameters. All other DHCP options are discarded.

You may notice that, if you use IPCONFIG or WINIPCFG on a RAS client to look at lease information, it has null dates (ie. Jan 1, 1980). When the client disconnects, the IP address will be released back to the RAS server, NOT back to the DHCP server. This causes a lot of confusion when people expect to get their IP addresses back to the DHCP server. These will only be released back to DHCP when the RAS service is stopped and then the lease expires in due course.

Thanks to Peter Smith