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Windows Server: Server Leases a Large Number of DHCP Addresses

Article Summary: This article provides information on what causes a Windows server to lease many DHCP addresses at once.

When viewing active leases on a DHCP server, you may notice that a server on the network has unexpectedly leased ten or more IP addresses. On a Windows DHCP server, this will appear similar to the image below, in which the server named updater.dpyoung.local has leased ten addresses:

This is normal behavior when a server has the Routing and Remote Access Service (RRAS) installed and enabled. RRAS is used to provide access to network resources for clients in other locations. It typically provides virtual private network (VPN) access, though it can also provide dial-up access if one or more modems are installed in the server.

When a remote client connects to an RRAS server, it has to be assigned an IP address in the local network's address range so that it can access resources on the network. RRAS can be configured to assign addresses to remote clients in one of two ways: either from a designated address pool or by using a DHCP server on the local network, as shown below:

When an RRAS server is configured to assign addresses using DHCP, it leases addresses from the DHCP server in blocks of ten. One address is assigned to the RRAS server's adapter, and the other nine are assigned to clients as they connect. Client-assigned addresses are unassigned as clients disconnect, but if all nine addresses are assigned to clients, the RRAS server leases another block of ten addresses from the DHCP server. This is why it may appear that the server is leasing an unusual number of DHCP addresses.

More information about this behavior is available here: RRAS and DHCP.

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ID de l'article : SLN285509

Date de la dernière modification : 09/22/2014 02:33 PM

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