Splitting up DHCP by Device Type

By itmanagement ·
Currently we have a 24 bit subnet at each site.

The problem:
We are running out of IP addresses rapidly.

The ranges set for different device types was inadequate and my predecessors then used any available IP address and reserved it for that device (eg. Printers)

VLANs were implemented but for the wrong reasons and so will be removed to flatten it out again and won't be implemented again unless necessary.

The solution I'm proposing:
We implement a new 16 bit subnet at each site.
For example

Servers and Core Devices will go in the range - 254

Printers will go in the range - 254

Thin Clients will go in the range -

Windows Workstations and Laptops will be put in the range - 254

VPN clients and dial in clients will be allocated an address in the range - 254

Future plans include quaranting clients at risk / devices plugged in to our network that are not under our control into the range - 254

The Implementation:
This is where I am a bit of a loss. The first DHCP scope I created worked fine ( - 254 / 16 bit subnet mask)

When I tried to implement a second scope of - 254 DHCP refuses and claims that the scope overlaps.

So my question is, how do I configure DHCP on Server 2003 to auto assign devices into specific ranges based on their Vendor ID?

We have Cisco 2900 series switches for now and I am somewhat loathe to put in VLANs and make it too complex as I'm a Windows Sys Admin and would be a bit out of my depth if I went too hard core on the Cisco side.

I've done a bit of reading on Vendor ID's and classes but come away with no real steps for testing it out and how to implement it.

Any advice would be greatly appreciated.

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All Answers

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assign by MAC address

by CG IT In reply to Splitting up DHCP by Devi ...

As far as DHCP, using a Class B will give you more subnet availability, but not sure why you don't like VLANs. VLANs can provide you with addedd security.

If you run IPv6, there is a new capability in W2008 server for linklayer control based on MAC address. See Microsoft Technet for full details.

Here's a MS Team blog on it.

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VLANs are OK

by itmanagement In reply to assign by MAC address

It's not that I don't like VLANs, I just don't want the added administrative overhead of having to change a port to VLAN2 manually if we move a printer or plug in a new device.

If I can get it working quickly and easily through the Dynamic VLAN option I'll be over the moon and will be more than happy if it works properly.

It's not so much the technical side but the management side to keep the devices separate for ease of administration. It also means I can have TFTP set up for one scope and the Wyse terminals can go to the WDM server and do their thing, but the PXE boot ROM on the workstations / laptops don't then try to pul down the same.

Not sure if I can run IPv6 atm as some of our thin clients are pretty old. Will look into it though :)

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Here's a Technet article on how to assign address

by CG IT In reply to VLANs are OK

using the MAC address [unique identifier]

The reservation will always assign the same address to the same device.

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Reservations not sufficient

by ian.wall In reply to Here's a Technet article ...

Hi, sorry this is the account I normally post under.

Reservations are an option but what we are trying to do is this:
1) Client boots up
2) Client sends a packet to the DHCP Server and tells the DHCP Server it is a Wyse Device for example
3) The DHCP Server responds with an Offer of a lease within the designated Wyse DHCP Scope.
4) The Wyse device then accepts the lease and is on the same IP range as all the other Wyse devices.

I know this can be done by using DHCP Vendor Classes and possibly the network quarantine components but it's finding out how.

How do you configure the DHCP Server to only pass out IP addresses from a specific range to Wyse devices?
How do you then set the default DHCP Scope for devices that aren't covered by the Vendor classes?

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