[NCLUG] PPP and IP addresses

[Barbara Hayes]

A far better explanation than I got when researching the first time,
thanks much.

barb.
>On Fri, 11 Jan 2002, Charles Clarke wrote:


>http://www.ietf.org/rfc/rfc2131.txt is the DHCP RFC.
>
>If you are renewing a lease, you don't specify your address, the
>server knows it.  If rebooting, you do request the old address.
>You can use the old until it expires or you get a decline from the
>server in response to a request.
>
>Unless configured specially by the admin, most DHCP servers will renew the
>same IP address as long as you want.
>
>Most clients don't release the old address unless they know they are
>moving between subnets.
>
>ATT Broadband (which I just cancelled due to them cancelling my new
>account that I had gotten after the old one didn't work for 30 days and
>most of the tech support being idiots - they wanted me to wait 1.5 weeks
>for a new modem to be brought by a truck to replace my current modem
>because "the modem is associated with the account")  would give an initial
>lease of 1 hour and then when you renewed would give you a lease of 4
>days.  Now, in my view, 4 days kinda defeats most of the benefits of DHCP.
>Assuming most folks would be on less than 8 hours a day, you could, at
>least, double the # of machines that could be supported by a set # of IP
>addresses by setting the lease time to 4 hours(which most would renew
>after 2).
>
>charles
>
>--------------------------------------------------------------------------
>  Domain hosting from $15/month with error log analysis and link checking.
>  http://www.clarkecomputer.com/sig.html       domains at clarkecomputer.com
>
>On Fri, 11 Jan 2002, J. Paul Reed wrote:
>
>>  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
>>
>>  _______________________________________________
>>  NCLUG mailing list
>>  NCLUG at nclug.org
>>  http://www.nclug.org/mailman/listinfo/nclug
>>
>
>_______________________________________________
>NCLUG mailing list
>NCLUG at nclug.org
>http://www.nclug.org/mailman/listinfo/nclug


--