How to setup multiple scopes on Windows Server 2012 R2 DHCP

Question

_{Saturday, November 19, 2016 10:47 PM}

Hello,

I am hoping someone can give me guidance on configuration of multiple scopes on DHCP.  Presently, I have one scope on my DHCP server - 192.168.1.x /24.

Due to growth and modern devices it has been requested of me to setup DHCP as follows:

1.  192.168.1.1 - x static for servers, routers, switches, etc.

2.  192.168.2.1 - x dynamic addressing for workstations

3.  192.168.3.1 - x dynamic addressing for mobile devices

Default gateway of 192.168.1.254.

It has been suggested that we change the subnet mask from /24 to /21.  That is indeed one way of accomplishing what we need to do with what we have, but, that means changing everything to the new subnet mask.  The likely hood of missing something is - in my mind - large. 

I know what I want to do with DHCP Relay Agent on the Cisco SG300s can be done.  Just not sure of how all the pieces go together.

Any guidance is greatly appreciated.

Thanks

All replies (3)

_{Monday, November 21, 2016 2:10 AM ✅Answered}

Hi Tim A. Fleming,

>I am hoping someone can give me guidance on configuration of multiple scopes on DHCP. 

>It has been suggested that we change the subnet mask from /24 to /21. 

1. The purpose to change the subnet mask is to add the host number in one subnet; the purpose to configure multiple scopes is also used to increase the IP address range to assign for clients. Both of the methods are used to rise the IP address number that can be assigned to clients, so you only need to choose one of methods to achieve your purpose, I would suggest the later one, since you want to assign different clients to different subnets;

2. For clients in different subnets from DHCP server, we need to set DHCP relay agent, for example, if the DHCP server's IP is 192.168.1.x in subnet 192.168.1.0/24, then for subnet 192.168.2.0/24 and 192.168.3.0/24, you need to set DHCP relay agent on network devices (Cisco SG300s).

(As mahelsay has mentioned DHCP superscope, as far as I'm concerned, it's not necessary, superscope is used to ease the management, the work theory is the same with common DHCP scopes.)

3. For those clients that you want to assign static IP addresses, you'd configure DHCP reservations for them. I'd recommend configuring static IP addresses directly on those machines, this is more secure in case DHCP server is inaccessible.

Best Regards,

Anne

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_{Sunday, November 20, 2016 6:53 AM | 1 vote}

Hi Tim,

firstly since your DHCP server is in 192.168.1.X subnet then most important thing is to not forget to make a DHCP super scope after adding the extra scopes 192.168.2.x and ..3.x

reason for that is by default DHCP will lease IPs only for requests in same subnet. to make it release IPs for the other scopes it should be included in a super scope.

secondly, to serve clients in remote subnets or VLANs you will need a DHCP relay agent or you will need to allow broadcast traffic on the devices separating the subnets.

with above two points in place I don't see a reason to change subnet masks to /21.. would you clarify again what was the cause of this suggestion?

Thanks and please mark the post as helpful if you find it adding a value to you.

Mahmoud

Microsoft CTS

Thanks Mahmoud

_{Monday, November 21, 2016 4:24 AM | 1 vote}

Thanks Anne for your reply... @Tim: kindly mark posts as helpful as it's really helpful and rich in information. Also let us know if you still have any questions Thanks Mahmoud

Thanks Mahmoud