Hi! I have computers running Windows Xp, and 7 in my network, and every computer is connected to a Switch and the Switch to a Router that generates the IP's (dhcp). My problem is that I have an "Apliance" (Telephone system) as a dchp for the IP Phones connected to it (actually the phones are taking the dchp from the router too). I do not undersand how a computer goes behind the router to the "Appliance" and take the IP address from it instead of the router (how are they connected I think is impossible). See how my network is phisically. http://www.realphotosnyc.com/network.jpg Is there any command I can run from the stations and says, hey you must take the dhcp from the router not the "Appliance"? Thanks!! P.S. I know I can't have 2 dhcp server running on the same network, but I do not have access of the Telephone system administration console. abasi

Short answer, nope... Understanding how DHCP works will help you understand how this needs to be resolved. Basically, DHCP does this: 1, DHCPDiscover Broadcast by a DHCP client when it first attempts to connect to the network. The DHCPDiscover message requests IP address information from a DHCP server. 2. DHCPOffer Broadcast by EACH DHCP server that receives the client DHCPDiscover message and has an IP address configuration to offer to the client. The DHCPOffer message contains an unleased IP address and additional TCP/IP configuration information, such as the subnet mask and default gateway. More than one DHCP server can respond with a DHCPOffer message. The client accepts the best offer, which for a Windows DHCP client is the first DHCPOffer message that it receives. 3. DHCPRequest Broadcast by a DHCP client after it selects a DHCPOffer. The DHCPRequest message contains the IP address from the DHCPOffer that it selected. If the client is renewing or rebinding to a previous lease, this packet might be unicast directly to the server. 4. DHCPAck Broadcast by a DHCP server to a DHCP client acknowledging the DHCPRequest message. At this time, the server also forwards any options. Upon receipt of the DHCPAck, the client can use the leased IP address to participate in the TCP/IP network and complete its system startup. This message is typically broadcast, because the DHCP client does not officially have an IP address that it can use at this point. If the DHCPAck is in response to a DHCPInform, then the message is unicast directly to the host that sent the DHCPInform message. So basically, because of the highlighted sections above your only option is to eliminate one of the DHCP servers...or to somehow keep the clients DHCPDiscover from getting to the undesirable DHCP server (if on the same subnet I don't think there's a good way to do this. If on a different subnet, remove the relay agent). Read more here: How DHCP Technology Works http://technet.microsoft.com/en-us/library/cc780760(WS.10).aspx

Hi abasi, Thanks for posting here. I think you should split computers and telephones into different networks by creating two VLANs( if it is a third layout switch) or physically isolated networks and setting DHCP relay if you want keep using single DHCP device. Thanks. Tiger Li Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading t