How can I setup dhcpd to renew lease with a diffrent Ip each time...
dhcp1 at thehobsons.co.uk
Thu Jul 6 15:56:34 UTC 2006
David W. Hankins wrote:
>On Thu, Jul 06, 2006 at 05:07:32PM +0200, Sébastien CRAMATTE wrote:
>> I'm working for a cable operator and I would like to know how can I
>> the dhcpd to renew lease with a new IP each time...
>There's no way to do this with the ISC DHCP software distribution as
>we release it.
>> Currently my CPE keep always the same IP and this is a problem because
>> they have nearly a fixed address ....
>'Nearly' is a more important distinction to me than you seem to
>Even if you gave out a random IP address, what makes you think your
>customers won't use dynamic DNS to locate their systems?
>Randomizing IP address allocations doesn't win you anything, so all
>it does is help things break more often and give your customers poor
>I strongly advise against this practice.
Always the diplomat !
If Sébastien cares to look back through the
archives, he will find that not everyone is as
diplomatic as that. I'd avoid shooting the
messenger, since I'm sure it's higher management
that have 'invented' this 'new' technique and
demanded it's implementation.
In short, forcing address changes on customers WILL break things.
For example, the download that's been going for
two hours and will complete soon - address
changes, connection broken. So what will the
customer do ? Try again ! So unless they (or the
software they use) is capable of restarting the
transfer, then they download all that data again
- it could be 4GB of a 4.7GB DVD (legal)
download. That's bad for you, it's bad for the
server at the other end, and it's bad for the
Of course, this will be worst for those customers
who aren't technically literate and least likely
to know about 'reget' and such things. They will
simply get to know that their downloads break
every so often while their friends on other ISPs
have no problem.
It will not however stop people using a dynamic
dns service to host stuff - such systems were
specifically made to work around
stup^H^H^H^Hmisguided ISPs who think dynamic
addresses are a good idea.
Then of course it means you have more record
keeping to keep track of who had what address &
when - for dealing with complaints.
It also makes the problem worse where someone
gets their email blocked because another customer
used to have that address and was being used
(without their knowledge most likely) to spew out
If you MUST stop people running servers etc, then
the correct way to do it is by filtering the
connections. If your only reason is to control
upstream bandwidth then apply traffic shaping. If
you attempt to do either by address hopping your
clients then it WILL fail, but in doing so you
find yourselves derided by technical users (who
will know what you are doing and how to work
around it), and grumbled at by non-technical
users (who will simply get to know your service
I strongly recommend going back to management and
explaining that it won't work - it will just get
you a bad reputation. Unless you have a monopoly
then the result is that you'll lose customers to
other ISPs who don't run a broken network.
It's actually in your own interests to make
clients have as static an address as possible
(best still is static assignments) - it's going
to be much easier to monitor and control that way.
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