ISC DHCP server ignores fixed address specification for Circuit-ID

[codedd713]

Thank you for that information! If the host declaration (even if on a different subnet) takes higher precedence to the client's subnet, it would really explain quite a bit.

But exploring on that front, here is something I came across on the ISC portal describing the dhcpd.conf file, quoted :

Link : https://www.isc.org/wp-content/uploads/2017/08/dhcp43.html

"
When dhcpd tries to find a host declaration for a client, it first LOOKS FOR A HOST DECLARATION which has a fixed-address declaration that lists an IP address THAT IS VALID FOR THE SUBNET or shared network ON WHICH THE CLIENT IS BOOTING. If it doesn’t find any such entry, it tries to find an entry which has no fixed-address declaration.
"

- pardon the CAPS, just wanted to place that in focus

Would this suggest that dhcpd picks the host declaration that is within the subnet of the client, and not other subnets?

Host declarations do support circuit-id. I will try using class declarations.

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Date: Tue, 20 Nov 2018 21:31:10 +0000 From: Simon Hobson <dhcp1 at thehobsons.co.uk> To: Users of ISC DHCP <dhcp-users at lists.isc.org> Subject: Re: ISC DHCP server ignores fixed address specification for Circuit-ID Message-ID: <EA20386E-2560-48C7-A76A-94F20A22CF01 at thehobsons.co.uk> Content-Type: text/plain; charset=us-ascii codedd713 <codedd713 at protonmail.com> wrote: > I observed this behavior (below) on ISC DHCP server. Was wondering if this is to be expected or perhaps I overlooked some element. Yes you've overlooked a critical bit of knowledge - something that's tripped up a few people over the years. All host declarations are global in scope - even when written within a subnet declaration. So the host statement matching the MAC address will always match - even when the client is in the other subnet. This may well prevent the other host declaration from matching - don't know what happens if two host declarations match a client. Also, I don't know if you can match on that option (circuit ID). AIUI there are only a small number of fields you can match on within a host statement. ------------------------------ Message: 3 Date: Tue, 20 Nov 2018 21:45:38 +0000 From: Patrick Trapp <ptrapp at nex-tech.com> To: Users of ISC DHCP <dhcp-users at lists.isc.org> Subject: RE: ISC DHCP server ignores fixed address specification for Circuit-ID Message-ID: <1D507D610594D14F86D40D77C17E9E665761F9DA at EXCHANGEDSB.ruralnex.com> Content-Type: text/plain; charset="us-ascii" Probably irrelevant to the larger conversation, but I am successfully using circuit ID to determine if a host belongs to a class. I only share that in case it's helpful to the OP if their host statements turn out to not use circuit ID like desired.
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