vSwitch, PortGroups - DHCP/RELAY Server Windows Server

[Maxhurales]

Hi everyone from this community!

I'm having problems to overcome a configuration and I hope someone can help me.
The situation is this:

VMWare 6.5

VM: DHCPServer with Relay DHCP Agent installed on same Windows Server 2012 (172.124.10.10) and serving IPs to network 172.124.10.0/24

LAN:

172.124.10.0/22  >  vlan 10: STUDENTS

20.160.11.0/24    >  vlan 20: TEACHERS

20.170.12.0/24    >  vlan 30: OTHERS

What I like to do is to configure the VM (DHCP/RELAY AGENT SERVER) to allow DHCP to serve addresses to the 3 networks.

This is what I have done:

- As I don't have enough physical adapters I used one vSwitch that I had already created but I created 3 NEW switch port groups "PGStudents", "PGTeachers", "PGOthers".

- Then I configure the number of the vlan on each port group.

- Then I added two network adapter to the DHCP/Relay Server and set the portgroups on each adapter.

- I configure DHCP Relay Agent on the server:

          . Added the interfaces

          . Configure the IP of DHCP server on the Relay DHCP server (the same server)

          . Added two new scopes on the DHCP

But it isn't working. It does not serve any IP on the vlan20 or vlan30.

* There is a switch in between vlans of course but I need to configure the DHCP Relay on the actual server.

What I'm doing wrong? What are my mistakes? Does it makes any sense?

Could you help me, give me a hand or some advices?
Thank you so much!!!

[HassanAlKak88]

Hello,

I guess you have to configure DHCP helper for each VLAN on your Switch.

Please consider marking this answer "CORRECT" or "Helpful" if you think your question have been answered correctly.

Cheers,

VCIX6-NV|VCP-NV|VCP-DC|

@KakHassan

linkedin.com/in/hassanalkak

[Maxhurales]

Hi Hassan,

First of all thank you for your answer and kind help.

Regarding to DHCP helper, actually that's exactly what I wanted to avoid by using instead DHCP Relay Agent on Windows DHCP Server.

Isn't that possible?.

I mean, instead of configuring the switch DHCP helper to forward the pettitions to the right DHCP scope what I like to do is to use DHCP Relay Agent to do this task and not to have to configure anything additional on the SW.

From what I understood that's how DHCP Relay Agent works on Windows Server or am I mistake?

Thank you very much
Best regards!

[HassanAlKak88]

Hello,

I don't have experience with DHCP relay in windows, but i am from network perspective, dhcp traffic (Broadcast traffic) sent from VLAN to other VLAN, without dhcp helper the packet dropped.

All our configuration with similar case (When DHCP clients and associated servers do not reside on the same IP network or subnet), we use the DHCP helper on physical switches.

Can you clarify, why are you avoiding the use of helper in switches ?

Please consider marking this answer "CORRECT" or "Helpful" if you think your question have been answered correctly.

Cheers,

VCIX6-NV|VCP-NV|VCP-DC|

@KakHassan

linkedin.com/in/hassanalkak

[HassanAlKak88]

And noting as I understand from the following YouTube video, you have to configure the router as windows machine and implement the Agent there:

    How to Configure DHCP Relay Agent in Windows Server 2016 - YouTube

Please consider marking this answer "CORRECT" or "Helpful" if you think your question have been answered correctly.

Cheers,

VCIX6-NV|VCP-NV|VCP-DC|

@KakHassan

linkedin.com/in/hassanalkak

[Maxhurales]

Hello again Hassan,

And once more thank you for your help.

Switches are administrated remotely and that's why I wanted to use DHCP Realy Agent on Windows so this way I don't depend on others

to do the configuration but if it is necessary that's what I'll do.

So if finally I choose to follow that line, to configure DHCP helpers on the SW, I have only one more question if I may.

RIGHT NOW THE CONFIGURATION IS IS THIS:

LAN (VLANs) --> SW --> FW

FW --> SW --> LAN (VLANs)

WHERE LAN HAS:

172.124.10.0/22  >  vlan 10: STUDENTS

20.160.11.0/24    >  vlan 20: TEACHERS

20.170.12.0/24    >  vlan 30: OTHERS

Clients from LAN 20 AND LAN 30 have visibility of LAN 10 (where the DHCP server is installed).

So If DHCP Helper is configured on the switch interfaces (on the interfaces connected to VLAN 10, 20 AND 30) does my DHCP server need to have one nic per vlan?

I mean, do I need to add two nics (apart from the one that already has serving ips to VLAN 10) in order to work?.

Or since VLANs 20 and 30 have visibility of VLAN 10 (where DHCP server is) no further configuration is needed on DHCP server?

Because as I understand:

Client from VLAN 20 send a DHCP resquest

SW DHCP Helper receive this request and add head 82

Then send a unicast request to the DHCP server (on VLAN 10) ip: 172.124.10.10

DHCP server replies this request and send offer to DHCP Helper on SW (unicast)

And DHCP Helper send this request to client

Is this correct?, and if so, I do not need to add two more nics on the DHCP due that DHCP helper adds the 82 head to the unicast request and DHCP knows what IP range use to assing the IP because it has 3 scopes configured per range.

Right?

Thank you very much and sorry if the questions are too basic but I never did this before and I'm a bit too much lost.

Best regards!

[HassanAlKak88]

Hello Dear,

Noting that no need to configure new interfaces in DHCP server.

All what you need, is to configure the helper for each VLAN, and create the normal scopes from DHCP servers.

So when a client request a DHCP IP address, the broadcast traffic received by L3 device will be forwarded to the DHCP Helper IP if exist else it will be dropped.

Then the L3 device forward a uni-cast traffic to dhcp server. DHCP server check if there a scope for this request and reply by an IP address with all options needed.

Find the below:

Please consider marking this answer "CORRECT" or "Helpful" if you think your question have been answered correctly.

Cheers,

VCIX6-NV|VCP-NV|VCP-DC|

@KakHassan

linkedin.com/in/hassanalkak