using microsoft 2016 DHCP Server

[moman62]

I have a cisco 3750 poe switch and instead of configuring dhcp on the device, I would like to use microsoft dhcp server to allocate the ip addresses etc.

I assume I have to use something called ip helper-address to make this possible? My dhcp server ip is:

192.168.75.5 255.255.255.0

my vlans are:

vlan 60

ip address 192.168.60.1 255.255.255.0

vlan 80

ip address 192.168.80.1 255.255.255.0

[Georg Pauwen]

Hello,

indeed, what you need to configure is (marked in bold):

interface vlan 60

ip address 192.168.60.1 255.255.255.0

ip helper-address 192.168.75.5 

!

interface vlan 80

ip address 192.168.80.1 255.255.255.0

ip helper-address 192.168.75.5 

[Deepak Kumar]

Hi,

Yes, You are correct and you need ip helper-address command under the SVI.

vlan 60

ip address 192.168.60.1 255.255.255.0

ip helper-address 192.168.75.5

!

vlan 80

ip address 192.168.80.1 255.255.255.0

ip helper-address 192.168.75.5

[Richard Burts]

Georg and Deepak have provided correct explanations about using helper-address. I would like to address another aspect of the original post. I note that the address of the DHCP server is different from the 2 vlans described on the switch. So the switch must have a route to subnet 192.168.75.0. And the router/switch where that subnet is must have routes to reach 192.168.60.0 and 192.168.80.0.

HTH

Rick

[Richard Burts]

Having thought a bit more about this post I realize that there is something that we do not know about this environment and it could be quite significant. We do not know whether this 3750 has ip routing enabled and is providing the layer 3 routing for these vlans or whether this 3750 is operating as a layer 2 switch and the layer 3 gateway is on some other device. Georg, Deepak, and I had assumed that the 3750 was routing for these subnets. If that is not the case then our advice needs to be revised. The helper-address needs to be configured on the device that is providing the layer 3 routing for 192.168.60.0 and 192.168.80.0.

HTH

Rick

[paul driver]

Hello
As others have mentioned you can forward client dhcp requests towards your widows server by applying the helper address on the l3 interfaces of the vlans you wish these client requests to be forwarded from.

However by enabling this helper address you will also by default enable udp flooding for other udp ports which you may wish to turn off if they are not required.

Example:
int vlan xx
ip helper-address <dhcp-server>
exit

no ip forward-protocol udp domain
no ip forward-protocol udp time
no ip forward-protocol udp tftp
no ip forward-protocol udp nameserver
no ip forward-protocol udp tacacs
no ip forward-protocol udp netbios-ns
no ip forward-protocol udp netbios-dgm

[moman62]

I do have ip routing turned on the 3750 switch

[moman62]

also for the vlans on my switch, do I need to configure any switchports? or just leave alone?

ex:

int gi 1/0/1

switchport mode access

switchport access vlan 60

[paul driver]

Hello

Yes any end hosts need to connect to the switch via access ports  so you would then configure those port in and administrative mode of access and assign the necessary vlan to them 

[Georg Pauwen]

Hello,

on a side note, make sure you have 'spanning-tree portfast' configured on the ports as well, otherwise the DHCP requests from your clients will timeout before reaching the server...

int gi 1/0/1

switchport mode access

switchport access vlan 60

spanning-tree portfast

[moman62]

since I will be configuring  (2) different scopes on the DHCP, wouldn't that require (2) different ip helper-addresses?

vlan 60

ip address 192.168.60.1 255.255.255.0

ip helper-address 192.168.60.0?

vlan 80

ip address 192.168.80.1 255.255.255.0

ip helper-address 192.168.80.0?

[Deepak Kumar]

Hi,

Yes, It is still required and You must configure different Scope for each VLAN on your DHCP server. A Single DHCP SCOPE or POOL can't assignn the IP to two different VLANs. 

[paul driver]

Hello

---

@moman62 wrote:

since I will be configuring  (2) different scopes on the DHCP, wouldn't that require (2) different ip helper-addresses?

---

No you dont, That is unless the scopes reside on different servers then you do - so just to confirm only one helper address per dhcp server NOT per dhcp scope.