Add DHCP Scope for VirtualIP

[KingLoui]

Hi OPNsense folks,

I just set up my OPNsense with one WAN and one LAN interface.
Due to reasons I wan´t to add a second L3 Network in the L2 domain of my LAN Inferface.
Therefore I have added a VirtualIP to the LAN Interface which workes as expected.
But now I struggle to add a DHCP Scope for the VirtualIP range.
The DHCP section just offers me to configure IP´s our of the basic LAN Scope 192.168.1.0/24.
But not for the VirtualIP Scope 192.168.178.0/24.
Is there a way to add a Scope for that IP range from the VirtualIP?

Unfortunately I havent found a solution in the forum.

Many thanks and kind regards

[Saarbremer]

Hi,

the way you are trying to achieve is not what you want do. You cannot distinguish between IP ranges in the DHCP protocol setup phase with a client. Furthermore, you'd have interference with other protocols at a latter stage.

What you would have to do is to create another interface, assign the IP and configure DHCP server for it. You typically achieve that using different VLAN.

What exactly is it you want to achieve? Do you have managed switch(es) in use to deploy VLAN?

[KingLoui]

Thanks for your quick reply.
Unfortunately in my Network I have a L2 ETH2VDSL2ETH Bridge which is not VLAN segmentation ready.
What I want to achive was to have a separate Network controlled by my OPNsense while still offering the Fritz Repeaters the chance to communicate with the FritzBox using their separate 192.168.178.0/24 subnet.
I agree that distinquish between the two DHCP´s would not be possible for the devices on L2. Therefore my inititial thought was if I can only handout static DHCP reservations on the secondary Subnet 192.168.178.0/24.
So that only the two WiFi Repeaters in my Network will get the IP addresses out of this Subnet 192.168.178.0/24.
But I agree that this is a very uinique scenario.
Idealy a L2 segmentation via VLANs would be optimal but it´s unfortunately not possible in my scenario :-(

[Monviech (Cedrik)]

There can only be one DHCP Server per Layer 2 Segment (If there's no switch that can do some DHCP Snooping tricks).

That's because the DHCP Discover is a Layer 2 Broadcast. If there would be two DHCP Servers on the same Layer 2 Segment, a client would always get the response from the faster one.

[mgear]

Just to jump in here, what if we did have a switch that had ip-helper? I don't think opensense allows us to create a scope without L2 anyway.. I would love if it could do this.. otherwise, I have had to put a an L2 interface in each VLAN created on a switch in the past. It would be awesome to be able to just create a scope without the need of the intefrace creation also..