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Hi Frances,</div>
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Thank you for your quick reply.</div>
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That’s disappointing that tagged IPv4 is not supported.</div>
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During my initial research I did come across this thread from 2017 from this mailing list asking for something similar (or possibly the same thing? It's unclear)
<span style="color: rgb(0, 0, 0);"><a href="https://lists.isc.org/mailman/htdig/kea-users/2017-February/000826.html" rel="noreferrer noopener">https://lists.isc.org/mailman/htdig/kea-users/2017-February/000826.html</a>.</span></div>
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It does seem like an important feature for Service Provider type applications and is especially disappointing since Kea already has 90% of the features required for an application like this such as matching subnets based on relay ip or any other arbitrary value
(such as option 82 sub options) with flex-id.</div>
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Regards,</div>
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Dee-Jay Logozzo</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Francis Dupont <fdupont@isc.org><br>
<b>Sent:</b> Wednesday, October 1, 2025 6:22:22 PM<br>
<b>To:</b> Kea user's list <kea-users@lists.isc.org>; Dee-Jay Logozzo <dee-jay.logozzo@ursys.com.au><br>
<b>Subject:</b> Re: [Kea-users] Duplicate Subnets</font>
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<br>
Dee-Jay Logozzo writes:<br>
> I am unable to configure KEA to serve identical subnets to different networks.<br>
<br>
=> Kea does not support different networks with the same address space.<br>
<br>
> We have an MPLS Service-Provider style network I am configuring that would =<br>
> benefit from being able to provide DHCP for different segregated network se=<br>
> gments (vrfs) using overlapping (or possibly duplicate) subnets.<br>
<br>
=> so in fact you want to manage (tag, address) resources (vs the common<br>
address resources).<br>
<br>
> subnet with the prefix of '192.168.10.0/30' already exists<br>
<br>
=> note even you can avoid this error using for instance '192.168.10.1/30'<br>
(Kea raises the error only when the text representation of the subnet is<br>
the same as an already configured one: there are some cases where it can<br>
be useful to configure overlapping subnets in Kea) this does not solve<br>
your problem as the address is the primary (so unique) key for the lease<br>
databases so:<br>
- tagged IPv4 is not supported<br>
- you can't have a delegated IPv6 prefix sharing the address part with<br>
an assigned IPv6 address (not something valid in the real world BTW)<br>
I am afraid you have to run different instances of Kea not sharing the<br>
lease database (e.g. if you use MySQL the "name" of the database must<br>
be different between Kea instances).<br>
<br>
> As the IP subnets we use for the different network segments are often alloc=<br>
> ations from our customers, the likelihood for subnet collision is inevitabl=<br>
> e, but as they are segregated networks that does not cause any issues.<br>
<br>
=> here the problem is address collision. Of course if there is an<br>
easy way to avoid them there is also no reason to tag addresses so<br>
to allow address collision is an essential part of the problem.<br>
<br>
> We have considered running multiple distinct KEA instances, one for each cu=<br>
> stomer with dedicated configuration, however this is undesirable as it grea=<br>
> tly increases both the network design and system provisioning logic require=<br>
> d for the rest of our system, as well as reduces the system resiliency as e=<br>
> ach customer/network-segment would need its own load-balance/HA group inste=<br>
> ad of being able to pool all those server (or vm) resources into one larger=<br>
> load-balance/HA group.<br>
> We would much prefer to be able to have one KEA configuration covering ever=<br>
> ything.<br>
<br>
=> I am afraid that currently you don't have the choice...<br>
<br>
Thanks<br>
<br>
Francis Dupont <fdupont@isc.org><br>
<br>
PS: as far as I know you are the first to ask for tagged IPv4 support even<br>
one can believe that IPv6 should have removed interest for this...<br>
I leave my colleagues to add comments as IMHO it was a major gap in the Kea<br>
initial design but nobody complained in this list until today.<br>
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