[Solved] dnsmasq IPv6 leases without MAC address

[Starjumper2821]

Recently migrated from ISC to dnsmasq for DHCP and it's working, but something is confusing me. A few of the IPv6 leases in the table don't have a MAC address. But somehow they have a hostname.

Here a partially redacted screenshot:
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I do know that one of the clients without a MAC is a Linux Mint system, so Debian/Ubuntu base.

Is this supposed to happen? Evidence of a configuration error somewhere?

I thank any help you can give me in this regard.

[Monviech (Cedrik)]

The MAC address is only an assumption based on the DUID of the client.

We try to extract it here:
https://github.com/opnsense/core/blob/e209de9719943a5224a06f8e155629d1052ddcba/src/opnsense/scripts/dnsmasq/get_dnsmasq_leases.py#L67

If you check the dnsmasq lease file /var/db/dnsmasq.leases you wont find any MAC addresses for DHCPv6 leases, only the DUID and IAID.

[Starjumper2821]

Ah, I see. That makes sense. And based on what I just looked up on how a DUID is created, the leases without a MAC address have type 4.

Well, that answers that. Thank you very much for your help.