Different IP every time

Dario Protulipac dario at vodatel.hr
Tue Mar 6 17:00:25 UTC 2007


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 :)

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