DHCP "static" assignments

[Sten Carlsen]

On 12/08/13 13:33, Glenn Satchell wrote:
> On Fri, August 9, 2013 6:07 am, Sten Carlsen wrote:
>> On 08/08/13 21:26, Chris Buxton wrote:
>>> On Aug 8, 2013, at 9:21 AM, Sten Carlsen <stenc at s-carlsen.dk
>>> <mailto:stenc at s-carlsen.dk>> wrote:
>>>
>>>> It seems to me that the man-page is not quite in agreement with this:
>>>> ~~~~
>>>> The *host* declarations will only match a client if one of their
>>>> /fixed-address/ statements is viable on the subnet (or shared
>>>> network) where the client is attached. _Conversely, for a
>>>> __*host*__declaration to match a client being allocated a dynamic
>>>> address, it must *not* have any __/fixed-address/__statements. _
>>>> ~~~~
>>>> This text says "not have any fixed-address statements", it does not
>>>> say any fixed addresses in this subnet.
>>>>
>>>> I also find the following a bit confusing:
>>>> ~~~~
>>>> The /fixed-address/ declaration is used to assign one or more fixed
>>>> IP addresses to a client. It should only appear in a /host/
>>>> declaration. If more than one address is supplied, then when the
>>>> client boots, it will be assigned the address that corresponds to the
>>>> network on which it is booting._If none of the addresses in the
>>>> __/fixed-address/__statement are valid for the network to which the
>>>> client is connected, that client will not match the
>>>> __/host/__declaration containing that __/fixed-address/__declaration.
>>>> _Each /address/ in the /fixed-address/ declaration should be either
>>>> an IP address or a domain name that resolves to one or more IP
>>>> addresses.
>>>> ~~~~
>>>> What does it mean "will not match"? Does that mean that the client is
>>>> then an "unknown client"?
>>> These are both good questions.
>>>
>>> In my experience, one should never assume that the DHCP man pages are
>>> 100% accurate. They are not.
>> Maybe we could try to improve that situation? First step is to realize
>> what is not perfect.
>>> Regards,
>>> Chris Buxton
>> --
>> Best regards
>>
>> Sten Carlsen
>>
>> No improvements come from shouting:
>>        "MALE BOVINE MANURE!!!"
> There is no "they" in the solution to this, it's down to "us".
I think I used the term "we". :-)
>
> The various dhcpd man pages are quite long with related information in
> many places. Often it may be updated in one but not all, leading to
> inconsistencies. Perhaps we can work out a better description to go in the
> man page. Then a bug can be logged to update the appropriate text.
Right, I just don't think I have enough weight to do that, at least on
my own.
>
> S, in the spirit of offering solutions, my suggestion to "What does it
> mean "will not match"?" In my mind it means that it ignores that host
> statement. If there is no other host statement for that mac address, then
> it becomes an unknown client. Now how to word that is a clear and concise
> manner?
This interpretation is not what I had assumed, I had assumed that it
would still be a known host, only treated as if there was no
"fixed-address" in the host statement. I seem to be mistaken.
>
> "If none of the addresses in the /fixed-address/ statement are valid for
> the network to which the client is connected, that client will not match
> the /host/ declaration containing that /fixed-address/ declaration."
>
> "If none of the addresses in the /fixed-address/ statement are valid for
> the network to which the client is connected, that client will not match
> the /host/ declaration containing that /fixed-address/ declaration. The
> contents of that /host/ declaration will not be evaluated, and if there
> are no other matching /host/ statements then the device will be an
> "unknown client"."
This is clear on that point, just to be sure - is it also correct? What
will happen to other statements in that host statement?
>
> Alternatively under the section where "unknown clients" is defined there
> could be a statement clarifying how a client becomes known or unknown.
> Currently the definition is
>
> "An unknown client is simply a client that has no host declaration."
"An unknown client is simply a client that has no host declaration or
has a host declaration with "fixed-address" statements that are NOT
valid for the subnet that the host is attached to at this time."

One proposal.
>
> I'm not quite sure hot to reword this. Over to you.
~~~~
The /fixed-address/ declaration is used to assign one or more fixed IP
addresses to a client. It should only appear in a /host/ declaration. If
more than one address is supplied, then when the client boots, it will
be assigned the address that corresponds to the network on which it is
booting._If none of the addresses in the __/fixed-address/__statement
are valid for the network to which the client is connected, that client
will not match the __/host/__declaration containing that
__/fixed-address/__declaration. _Each /address/ in the /fixed-address/
declaration should be either an IP address or a domain name that
resolves to one or more IP addresses.
~~~~

~~~~
The /fixed-address/ declaration is used to assign one or more fixed
IP addresses to a client. It should only appear in a /host/
declaration. If more than one address is supplied, then when the
client boots, it will be assigned the address that corresponds to the
network on which it is booting._If none of the addresses in the
__/fixed-address/__statement are valid for the network to which the
client is connected, that client will not match the
__/host/__declaration containing that __/fixed-address/__declaration*/ effectively /**/annulling the host statement./*
_Each /address/ in the /fixed-address/ declaration should be either
an IP address or a domain name that resolves to one or more IP
addresses.
~~~~

The point in doubt here is then:
What about the other parts of that host statement? will e.g. a
"host-name" be ignored?

I have no clue. I would have to study the code for an answer, maybe
someone on the list knows that?
>
> regards,
> -glenn
>
>
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-- 
Best regards

Sten Carlsen

No improvements come from shouting:
       "MALE BOVINE MANURE!!!"

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