howto configure DHCP to reject renewal of lease

Simon Hobson dhcp1 at
Fri Oct 13 06:59:32 UTC 2006

Gilbert Coles wrote:

>Simon, you are definitely right and I thought about this all along but as
>you say some obstinate heads exist in the world thinking that IP rotation is
>the only way and this answer of yours is my final blow - that the world's
>most popular DHCP daemon doesn't do it, translating to: don't you dare ask
>me the ip f*&king rotation question again...

If management still insist on it, then my advice 
is to look for a job with a more enlightened ISP 
- don't wait till they go under and you're kicked 

>Guess the traditional way of doing it for ISPs is using RADIUS and PPP auth
>since Radius tends to switch IPs but I was and still am against IP rotation
>- it destroys the notion of "always on" in the case of ISPs. So really mine
>was just a confirmation question.

I'd always assumed it was different in 'dial up' 
situations, and re-use of addresses was a given 
since there are generally many more users than 
there are 'dial up' ports. Even with xDSL, there 
are still a fair number of users still treating 
it as dial up with a locally attached modem 
though I guess the user-port ratio must be moving 
close to 1.

Giving out a different IP each time a user 
connects is not necessarily bad, the user cannot 
have any existing connections to break. I do 
however wonder at the per month charge many make 
for fixed addresses (commonly £5/month here in 
the UK) when with DSL and a hardware router the 
user is going to be tying up and address 24x7 
anyway so it really doesn't cost anything for 
that address to be the same after a 30 second 
break !

My ISP automatically gives customers fixed 
addresses - dynamic isn't even an option I think !

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