change ip address every 6 hours

[Simon Hobson]

Yannick CHAMPS wrote:

>We are a new isp and now  in competition with the historical ISP which
>is switching ip adresses every 12h since its beginning and does not
>offer fixed ip address service.

Well in that case, go back to your management armed with the comments 
made earlier - ie it'll piss off customers, etc, etc - and suggest 
that instead of making yourself as bad as the opposition you could 
sell your services as "better by default".
FYI - my ISP offers fixed addresses on most packages free. In fact, 
on my package it isn't an option to have a dynamic address.
Other ISPs simply take the p**s and charge extra for fixed addresses, 
in fact one connection we have at a customer site has higher charges 
for the fixed IPs than for the connection - but not for too long as 
we plan to be ditching that and getting something better for less 
from an ISP who has a clue. If I were switching ISPs for my own 
connection, I would simply rule out any ISP that takes the p**s like 
that.


Remember, in these days of always on connections, you really don't 
save anything by forcing address changes - it's probably rare that 
you don't need enough address for all your clients.



As to how to do it, if your management really are that stupid, I'd 
suggest something like this - though it won't work on 6 hour slots. 
I'd also suggest looking for another job.


Break your pool into a number of ranges, and disable one of them. Eg :

subnet 10.0.0.0 mask 255.255.0.0 {
   range 10.0.1.1 10.0.1.254 ;
   range 10.0.2.1 10.0.2.254 ;
   ...
   range 10.0.10.1 10.0.10.254 ;
}

Now comment out the first range. Eventually, clients will be unable 
to renew leases in the range 10.0.1.x and so will have to get a new 
address. The maximum time taken will be your max lease time, after 
this time, re-enable this range and disable the next one - so clients 
with a 10.0.2.x address will eventually be forced to change.
Keep repeating this process until you reach the last range, then loop 
back to the beginning.

Clients will now see their address change on a seemingly random 
schedule. If they are lucky they'd go from (eg 10.0.2.x) to (eg 
10.0.1.x) and so get to keep their address for a while (at least the 
max lease time times the number of ranges you split your pool into). 
At the other extreme, if a 10.0.2.x client got an address in 
10.0.3.x, it would change again on the next cycle.


-- 
Simon Hobson

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