Different IP every time

Carl Karsten carl at personnelware.com
Tue Mar 6 17:15:08 UTC 2007

Dario Protulipac wrote:
> Dario 
> Simon Hobson wrote:
>> Dario Protulipac wrote:
>>> is it possible to force the DHCP server to give a client different IP
>>> address every time the lease expire? Something like the PPP LCP does.
>> Firstly, as far as I know, the PPP LCP does not specifically force a 
>> different address each time - you are probably just observing what 
>> specific implementations do.
>> As far as DHCP goes, the RFC requires the server to try and give each 
>> client the same address each time (not that Microsoft take any 
>> notice, their server ignores that along with several other 
>> requirements).
>> What is your reason for wanting this ? I don't think we've ever had a 
>> legitimate reason, usually it's "we are an ISP and my manager insists 
>> we do this to stop <insert whatever>". Changing the clients IP 
>> address is bad, really bad, and very dumb.
>> If that is the case, read on ...
>> It will not stop clients running server type applications (that's why 
>> there are dynamic dns services). What it will do is break a clients 
>> connections at regular intervals. Lets say you pick two hours, and a 
>> client tries to download a big file that takes 2 1/2 hours to 
>> download. After 2 hours (or less) the download will break, and the 
>> user will probably try again, and again, and again. Many clients 
>> (particularly http downloads) don't resume broken downloads so each 
>> time the user is downloading <some large volume> of data which is bad 
>> for the internet, bad for the server, and bad for you as the ISP.
>> Eventually your customers will find out why their downloads don't 
>> work and other connections get broken, and you will get "bad vibes" 
>> that will make any worries about customers running servers look 
>> trivial. Customers will leave as fast as they can and you will go 
>> bust. Frankly, that is what stupid ISPs deserve !
>> .
> The idea is to give 24 hour lease and then change the address. Managers 
> want that because t-com do this in Croatia (using pppoe), so the people 
> are used to that. Any way, I'm aware that this is not how DHCP should 
> behave, but they insist on this because this is FTTH service and they 
> want some limitation so they can sell other FTTx services on bigger 
> price. Since this is political and not technical issue any more, I'll 
> thank You for Your answers and stop this thread hoping that I won't be 
> forced do patch the server :)

It would be easier to randomly drop connections.

I know, I know... stop the tread...

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