[Kea-users] IP reservation for multiple MAC addresses

Marcin Romanowski marcin at nicram.net
Tue Sep 1 19:02:27 UTC 2020

wt., 1 wrz 2020 o 20:52 Robin Daermann <robin.daermann at ruhr-uni-bochum.de>

> Hi,
> On Tue, Sep 01, 2020 at 08:11:21PM +0200, Marcin Romanowski wrote:
> >Do you think that is correct? There shouldn't be / it can't be two the
> same
> >ip address in the same network, this is ip conflicts and L3 wont work
> >correctly.
> >
> >Opposite situation where you share the same mac but with different ip
> could
> >be considered as correct.
> Yes it is correct. Imagine for example having laptops with USB-C
> Ethernet Adapters/port-replicators/docks. Each adapter has its own MAC
> address and only one of them is used at a time. Due to obscure reasons,
> some users are dependent on specific IP addresses and would like to get
> them assigned independently of their Ethernet adapter.

No this configuration is still incorrect. From network engineer perspective
that configuration assumes that could be one ip address with different mac
addresses at the same time. This is a network issue. Don't do that.

If you want to share the same ip address with different devices consider
using option 82 and assign addresses based on port.

you also can make user class with test where you provide your mac addresses
as key and assign that class to reserved ip address. I've never do that
way, but could work.

> I know that we could use other criteria such as DUID for assignment but
> that is not an option because it has other disadvantages for us (i.e.
> they tend to change when reinstalling the OS or for other reasons).
> I wonder if it is possible when using a MySQL database for host
> reservations. Will try some things tomorrow...
> Btw: I am using Kea 1.6.3 on FreeBSD 12.1.
> Regards,
> Robin Därmann
> (Network Operation Center RUB)
> --
> | Robin Därmann                             Network Operation Center |
> | RS18625-RIPE                              Ruhr-Universitaet Bochum |
> | You always meet twice in a lifetime...                             |
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Marcin Romanowski / nicraM
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