Unanswered Question
Jan 21st, 2009


I know this might seem very novice but here goes. If I have a Windows 2003 server acting as a DHCP server with 2 different scopes (1 for computers, 1 for IP phones) and the phones and computers are on different VLANS how do I get the phones to pull IP addresses from the correct scope and vice-versa if they are both pulling from teh same server?

Thanks in advance!

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Roberto Salazar Wed, 01/21/2009 - 12:54

the hosts in the same vlan as the dhcp server will get a dhcp request that is broadcasted while the dhcp request from a vlan that is different from the DHCP offer will get a unicast request that will come from the dhcp relay agent which is signified by ip helper-address. This logically will be the way for the dhcp server to tell which scope to assign to what request.

angel-moon Thu, 01/22/2009 - 06:21

Thanks. Just to clarify, since the DHCP server will be handing out IP addresses for all vlans I just need to configure each vlan to use an IP helper-address that is within the same scope as the one I want to use for the other vlan correct?

Roberto Salazar Thu, 01/22/2009 - 08:51

The svi(interface vlan) that is in the different subnet than the DCHP server will each need an ip helper-address. For example, dhcp server (1.1.1.x) is in vlan 1 ( and the hosts are in vlan 2 and vlan 3 under interface vlan 2 and vlan 3 should should have "ip helper-address 1.1.1.x"


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