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I have an isc-dhcp-server running in a Docker container, which I configured with one subnet of 100 available IP @.

When starting my laptops (they are all running Linux OS), when they are requesting IP@, they are all offered with the same one by the DHCP server, even though they have different MAC@.

When I have a look at the /var/lib/dhcp/dhcpd.leases file, I see different "lease" lines, one per laptop, but with the same IP@.

Is there a specific configuration to make sure that the DHCP server assigns different IP@ or do you see what could be wrong here?

Bruno
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  • That smells as if the MAC address gets lost on the way, possibly in the bridge, and the server sees the same address for all hosts. – Simon Richter Aug 26 '21 at 08:37
  • Hmm no, the MAC @ is different when I look at the /var/lib/dhcp/dhcpd.leases. Only the uid and client-hostname is the same – Bruno Aug 26 '21 at 08:43
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    ah, the UUID overrides the MAC address as an identifier (this is useful for example for a client switching from wired to wireless). Your clients need to generate different UUIDs. – Simon Richter Aug 26 '21 at 08:52
  • Ah ok! I didn't know... many thanks for your help. And there is no way for the isc-dhcp server to ignore this value and rely exclusively on the MAC @? – Bruno Aug 26 '21 at 11:35

1 Answers1

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Correct thing to do is for DHCP servers to send same IP for same UUID so that roaming between wired and wireless is seamless.

To fix duplicate UUIDs the identifier on the clients should be fix. (this is a client issue, not server)

If you want to keep the old MAC based behavior you should be able to use ignore-client-uids true; as described at https://serverfault.com/a/977782/187998

NiKiZe
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