DHCP server scope on different subnet

[newbie Admin]

I may have word the title misleading but please bear with me.

I am looking for a way to assign Windows 7 client a subnet and allow it to grab any ip from DHCP scope. On my Windows Server DHCP I configured it to be superscope with 4 subnets (no real reason beside categorizing them for webexclusion list). I want to be able to tell a computer which subnet it belongs to and allow it to grab any IP address from DHCP.

Any idea?

I know this can be done as I "accidently" assign a client with subnet 192.168.2.x before but not sure what I did.

 

[boosted1g]

You cant just plug 12 PCs into a unmanaged switch and the single DHCP server know which of those PCs to assign to which subnet.

It sounds like you have already setup DHCP scopes to assign IPs for each subnet.
You either need routers for each subnet that can be your DHCP relay or managed switches with VLAN tagging (and then bridge the VLANs)

 

[newbie Admin]

That will work but not what I am aiming for. I like to be able to see those IP address in DHCP leases and DNS service.

 

[McHenryB]

If you are obtaining the IP address via DHCP you are also obtaining the netmask in the same way. Therefore there is no way to tell the client computer which subnet to use.

In other words - it can't be done. The nearest that you could do would be to assign a fixed address in the DHCP server to the client's MAC. As you say, there is really no good reason to subnet your network in this way.

 

[boosted1g]

Your DHCP server would still assign an IP and thus of course you would also see it in DNS tables. Why do you think this would not be the case?

 

[boosted1g]

If you are obtaining the IP address via DHCP you are also obtaining the netmask in the same way. Therefore there is no way to tell the client computer which subnet to use.

In other words - it can't be done. The nearest that you could do would be to assign a fixed address in the DHCP server to the client's MAC. As you say, there is really no good reason to subnet your network in this way.

With unmanaged switches and a single off the shelf SOHO routers this is correct.

By using a router for each subnet (and setting them to point to the Server for DHCP) you can use that router to then be the DHCP relay that will tell the DHCP server which subnet it is on so that it can use the right scope of DHCP addresses.

Then there is managed routers and switches where you can assign each port to a VLAN and thus the DHCP server can know which scope based off of what VLAN.

 

[McHenryB]

That does of course rely upon the client computer being plugged into a particular outlet.

If all the OP is concerned with is a webexclusion list can't he use the DNS names rather than IP addresses?

 

[boosted1g]

At that point the OP would have to edit configurations for each new computer or device, at which point he might as well just setup DHCP reservations based on MAC address.

 

[boosted1g]

At the end of the day there clearly has to be something that differentiates that computer in order to categorize it as one subnet or the other. It is either a setting on the specific PC, an identifier like it NETMASK or WINS name or its MAC address that is built into an exclusion/reservation list, or its something else physical like what port its plugged into. There is just no way around that.

 

[bill001g]

You can dynamical assign pc to vlans and as a byproduct different subnets using 802.1x or lldp but this is very much in the realm of enterprise lan installations.