How long is the lease on the IP address when issued to a RAS client from DHCP?

John Savill

March 4, 1999

1 Min Read
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A. When a RAS server is set to allocate IP addresses from DHCP, itgrabs n+1 addresses when the service starts, (where n is the number of dial-upinterfaces), and keeps them. Therefore, the lease time is largely irrelevant.When a client dials in, the RAS server issues one of these cached leases andthe RAS server maintains the lease on behalf of the client. The RAS server onlyrecords the address of the DHCP server and the lease parameters. All other DHCPoptions are discarded.

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

Thanks to Peter Smith

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