How to identify a client?

[Sten Carlsen]

You can give each client a unique ID, the method for doing this differs
among systems and sometimes it is used "as is" and sometimes with a
prepended \000

In MACOS there is a field in the TCP setup to put in the client ID, in
windows it is the computer name (IIRC), using the ISC dhclient, there is
an option in the conf file.

I have usually set the parameter in the client system and checked in the
leases file what has been sent in and used. Then I have made the host
statement with my fixed address and what else needed.

Tom Schmitt wrote:
> Hi,
>
> thank you for your answer. Your first solution doesn't work for me, because I have several different subnets. So I can't give the client the same IP-Address in different subnets.
> As a second point I don't know all the MAC-addresses before the clients is connected to the network.
>
> Your second solution I don't understand completly: Is the DHCP-identifier from the clilent the same, even if the MAC-address is changed?
>
> thanks,
> Tom.
>
> -------- Original-Nachricht --------
>   
>> Datum: Fri, 04 Jul 2008 18:27:27 +0200
>> Von: Sten Carlsen <sten at s-carlsen.dk>
>> An: dhcp-users at isc.org
>> Betreff: Re: How to identify a client?
>>     
>
>   
>> I have a similar situation, but with a few differences. I hope this 
>> could be an inspiration.
>>
>> I have made a host entry for each of the MACs (wired / wireless)they are 
>> each given the same IP, that works without any problem. I can even 
>> continue a download while switching form wired to wireless.
>>
>> The other thing I have tried is to have a host entry with a  option 
>> dhcp-client-identifier. IIRC this also works.
>>
>> Tom Schmitt wrote:
>>     
>>> And now comes the problem: In the WLAN the client is using another MAC
>>> (the one of the WLAN-card instead of the normal NIC) but the same name. So,
>>> if a client was first in a normal subnet, getting a lease and a DNS-entry,
>>> then the client is moving to a WLAN-subnet and comes with the same name but
>>> differrent MAC to the DHCP. The clienst is getting a new IP but no entry
>>> in the DNS because there is already an entry and the TXT-records says: Its
>>> not yours!
>>>
>>> So, for the time the old lease is valid, the client has no DNS-entry.
>>>
>>> What can I do to solve the problem?
>>> The only thing I could think of, was a shorter leasetime. But this is
>>> problematik for several other reasons. Abd beside: It wouldn't solve the
>>> problem, only make it happen fewer times than with a longer lease.
>>>
>>> Is there a best practice to avoid this problem? Do anyone else have the
>>> same problem?
>>>
>>>       
>
>   

-- 
Best regards

Sten Carlsen

No improvements come from shouting:

        "MALE BOVINE MANURE!!!"