DHCP Server for 2 subnet network

Question

_{Tuesday, February 27, 2018 8:18 AM}

Hi there,

I have windows server 2012 R2 on our office network: 172.16.128.0/24

I also have vlan for guests (192.16.128.0/24), current setup for ip address is to setup static, as time goes by many guests is coming to our office and many guests that have the rights to set the ip address static. Therefor my question is:

How to use DHCP server on our office network for our vlan guest..?

Best Regards,
Edward Sinaga

All replies (5)

_{Tuesday, February 27, 2018 8:38 AM ✅Answered}

Hi Edward,

On your DHCP server you can easily just add multiple DHCP scopes for different subnets.The only thing you really have to make work is the DHCP forwarding on your network router to forward the DHCP request from your clients using broadcast to the DHCP server in the different subnet.

Let's say your DHCP server already exists in a good standing in subnet 172.16.128.0/24 you have to set a DHCP forwarder  on the router (default gateway) of your 192.16.128.0/24 subnet to the IP address of your DHCP server in the 172.16.128.0/24 subnet.

Best,
Toby

_{Wednesday, February 28, 2018 6:49 AM ✅Answered}

Hi,

Thanks for your question.

Firstly, we should create a new DHCP Scope for VLAN guest. Then  we can setup a DHCP Relay Agent in VLAN guest by using Windows Server Feature “Routing and Remote Access Service”. The DHCP relay agent may in the same subnet with the clients, and in the DHCP relay agent, we need to set the DHCP server's IP address.

Please refer to the following link to deploy a DHCP relay agent:

/en-us/previous-versions/windows/it-pro/windows-server-2008-R2-and-2008/ff687684(v=ws.10)

https://www.sqa.org.uk/e-learning/NetInf101CD/page_76.htm

Please Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.

I also agree with Toby’s solution. This DHCP forwarding he mentioned, I think it is DHCP relay agent actually. A DHCP relay agent is any host that forwards DHCP packets between clients and servers. Relay agents are used to forward requests and replies between clients and servers when they are not on the same physical subnet.

So you may configure DHCP relay agent function on your Router as the default gateway  in subnet 192.16.128.0/24 .

Furthermore, some routers and Layer3 Switch are supporting for DHCP broadcast currently according to RFC 1542. That is said, you need to simply make configuration for these Router or Layer3 Switch supporting DHCP packet forwarded.

Reference for RFC 1542:

https://www.rfc-editor.org/rfc/rfc1542.txt

I appreciate your effort and cooperation. If you have any questions or concerns, don’t hesitate to let me know.

Wish you have a nice day!

Best regards,

Michael

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_{Friday, March 2, 2018 10:29 AM}

Hi Edward,

How are things going on? Was your issue resolved?

Please let us know if you would like further assistance.

Wish you have a nice weekend!

Best regards,

Michael

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_{Tuesday, March 6, 2018 3:04 AM}

Hi Toby & Michael thank you for the help, i managed to solved it by doing:

1. Set 2 DHCP scope: 1 for office & 1 for guest
2. Create 2 vlan on our layer 3 switch; vlan 100 (office), vlan 200 (guest)
3. Set ip dhcp relay agent on each vlan <ip helper-address>

and bingo all computers & mobile phones for guest are getting ip from dhcp scope 192.16.128.0/24.

Best Regards,
edward

_{Tuesday, March 6, 2018 4:32 AM}

Hi Edward,

I'm glad to hear that your issue was successfully resolved. Thanks for your posting and sharing here!

If there is anything else we can do for you, please feel free to post in the forum.

Wish you have a nice day!

Best regards,

Michael

Please remember to mark the replies as an answers if they help.
If you have feedback for TechNet Subscriber Support, contact [email protected]