[NCLUG] PPP and IP addresses

[J. Paul Reed]

On Fri, 11 Jan 2002, Barbara Hayes wrote:

> >You know how DHCP leases you an address, and you have to renew it from
> >time to time, and there is the possibility that you will be leased a
> >different address?
>
> Yes, but not during the same session - I was told at the time I
> investigated this that if you're on a lan, a "session" is the time
> between rebooots.

That's not quite true... a DHCP client is supposed to reverify its settings
based upon the lease time it gets each time it does so; if the lease is 5
minutes, and the DHCP client and server are both following the specs (i.e.
no Microsoft products), then, theoretically, your address could change
every 5 minutes.

You can request a lease of any length you want, but the server isn't
required to give it to you.

Similarly, you can request the same address, and most servers will give you
the same address anyway (if your address was changing every few minutes,
that would wreak havoc on TCP connections), but they're not required at all
to do so.

If they were, that would make DHCP useless.

> Don't know if there's an upper limit on this.

Whatever the lease is... I think the lease is given in seconds, and so
whatever the max value of that field in the DHCP config packet is.

Later,
Paul
    ------------------------------------------------------------------
    J. Paul Reed            preed at sigkill.com || web.sigkill.com/preed
    What's the point in being nuts if you can't have a little fun?
                                   -- John Nash, Jr., A Beautiful Mind