Please ignore me, I failed to notice that Francis had already answered.

On Wed, Oct 1, 2025 at 8:45 PM Darren Ankney <[email protected]> wrote:
>
> Hi Dee-Jay,
>
> In Kea, the subnet is just a label.  You should be able to do
> something like this:
> "subnet4": [
>  {
>    "subnet": "192.168.10.0/30",
>    "id": 1
>  },
>  {
>    "subnet": "192.168.10.1/30",
>    "id": 2
>  }
> ]
>
> However, kea-dhcp4 may then complain about overlapping pools.  Please
> do try this in a test lab before trying to use in production.
>
> Thank you,
> Darren Ankney
>
>
> On Wed, Oct 1, 2025 at 2:56 AM Dee-Jay Logozzo
> <[email protected]> wrote:
> >
> > Hi All,
> >
> > I am unable to configure KEA to serve identical subnets to different 
> > networks.
> >
> > We have an MPLS Service-Provider style network I am configuring that would 
> > benefit from being able to provide DHCP for different segregated network 
> > segments (vrfs) using overlapping (or possibly duplicate) subnets.
> > These segregated vrfs are able to talk back to the KEA instance via 
> > multi-homed DHCP Relays living in both the customer's vrf, and our 
> > dhcp-management vrf.
> > We are using Option 82 (sub-option 2) set individually by each DHCP relay 
> > to distinguish between each network within the KEA DHCP server.
> > Everything is working as expected with this configuration, the segregated 
> > DHCP clients are able to receive their specific allocation as per Option 82 
> > (using flex-id within KEA).
> > However, if we configure two different and segregated network pools to use 
> > the same subnet within the KEA kea-dhcp4.conf configuration file, KEA 
> > refuses to start with a 'DHCP4_INIT_FAIL failed to initialize Kea server: 
> > configuration error using file 'kea-dhcp4.conf': subnet with the prefix of 
> > '192.168.10.0/30' already exists (kea-dhcp4.conf:62:7)' error.
> >
> > As the IP subnets we use for the different network segments are often 
> > allocations from our customers, the likelihood for subnet collision is 
> > inevitable, but as they are segregated networks that does not cause any 
> > issues.
> > The only problem is that KEA refuses to start with such a configuration.
> >
> > Is this a supported configuration that I am missing the obvious solution 
> > for? Are there any available workarounds for my use-case? Are there any 
> > other solutions for such an issue?
> > We have considered running multiple distinct KEA instances, one for each 
> > customer with dedicated configuration, however this is undesirable as it 
> > greatly increases both the network design and system provisioning logic 
> > required for the rest of our system, as well as reduces the system 
> > resiliency as each customer/network-segment would need its own 
> > load-balance/HA group instead of being able to pool all those server (or 
> > vm) resources into one larger load-balance/HA group.
> > We would much prefer to be able to have one KEA configuration covering 
> > everything.
> >
> > Regards.
> >
> > Dee-Jay
> >
> >
> > Dee-Jay Logozzo
> >
> > IT Security Architect
> >
> > URSYS PTY LTD
> >
> > Level 1 / 459 – 461 Parramatta Road
> >
> > Leichhardt  2040 NSW
> >
> > E: [email protected]
> >
> > T: 02 8745 2841
> >
> > W: URSYS.com.au
> >
> >
> >
> >
> > --
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> > Contact us at https://www.isc.org/contact/ for more information.
> >
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> > [email protected]
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