Superscoping example

Spacer_08

Hey guys, I'm having some trouble understanding superscoping. Please find attached example below:




Say for example, I wish to add an extra workstation that has never before being booted up, and TCP/IP obtains address automaticly.. which DHCP server will it go to and which address will it use..the first that responds? So if i wanted this client to be given a subnet B address range rather than a subnet A one how can this be done when all workstations are connected through a hub before the router?

Thanks in advance!

Slowhand

To understand how a workstation obtains a DHCP address, it's important to understand the D.O.R.A. process. A workstation broadcasts to discover a DHCP server, and all DHCP servers on the same wire will respond. The first server to to successfully roll through all four steps with a workstation will be the one handing out an address and other servers' responses will be ignored by the workstation. In Windows, if you want a workstation (or any other piece of hardware with a NIC) to have a particular IP address, you can set up a DHCP reservation very easily. A reservation is done by the workstations MAC address, which never changes, (unless you replace the network card,) so the DHCP server will always give the designated IP address to that device.

Spacer_08

Hey Slowhand, thanks for the reply. The thing im struggling with is how the B clients in this example have all been given the 10.222.222.x address ranges and the A clients have all been given the 10.111.111.x address ranges. Assuming these servers were set up with no reservations, how did B clients know to use DHCP server B, and how did A clients know to use DHCP server A. Thanks again!

royal

Read this blog entry which is in my stick post:
http://www.shudnow.net/2007/11/20/dhcp-scope-vs-superscope/

Pash

Spacer_08 wrote:

Hey Slowhand, thanks for the reply. The thing im struggling with is how the B clients in this example have all been given the 10.222.222.x address ranges and the A clients have all been given the 10.111.111.x address ranges. Assuming these servers were set up with no reservations, how did B clients know to use DHCP server B, and how did A clients know to use DHCP server A. Thanks again!

In answer to your question SPacer, it doesnt, like you say without reservations there is no fancy backend work going on here. Try not to pay to much attention to how conveintently the IP's are dealt out here.

http://technet2.microsoft.com/windowsserver/en/library/3967ddab-0b28-4959-8b4d-3052c178731b1033.mspx?mfr=true

This link may help you understand the reasons to use superscopes a little better. It's a good refresher for me also.

Cheers,

dynamik

Spacer, we all hate that diagram. The explanation MS Press provides for this diagram is abysmal. They imply that under this configuration, machines will always get addresses from the subnet that they currently have.

The point the book is trying to make is that using a superscope and excluding a subnet on each server prevents the DHCP servers from sending a NACKs for renewals on a subnet they're not serving (which might occur if you had two servers configured with one subnet each). It will not guarantee address assignment.

Spacer_08

Thanks very much for clearing that up guys.. 3 consecutive IP address Is too suspicous for me to pass up! Thanks again ;p