Client IP Address Assignment
Updated: April 30, 2010
Applies To: Windows Server 2008, Windows Server 2008 R2
Typically, when you have slower WAN links or when you have dial-up links, you place a Dynamic Host Configuration Protocol (DHCP) server on each side of a remote site connection. Installing the DHCP service on a calling router or other server at a branch office lets branch office clients obtain IP addresses from that server.
However, a DHCP server located in one subnet can support other subnets. If no DHCP server is located at the branch office, when a client at the branch office requests an address, the calling router can forward the client’s request across the dial-up or VPN link to the DHCP server in the main office, which then leases the client an address. For this to work, ensure the following:
The calling router contains the DHCP Relay Agent (the DHCP Relay Agent component is added with the internal interface by default).
The calling router is configured with the DHCP server’s IP address.
The site-to-site connection is a persistent connection.
For an on-demand connection, if the DHCP Relay Agent is installed on a branch office router, this can cause the router to dial the main office router (for a non-VPN dial-up connection) or the local ISP (for a VPN connection that uses a dial-up link to the ISP) every time a DHCP packet is sent by a computer in the branch office network. Therefore, if you deploy an on-demand connection, install the DHCP service in the branch office and uninstall the DCHP Relay Agent on the calling router.