Re: [TCLUG:21970] Should DSL or Cable modem

To: <tclug-list@mn-linux.org>
Subject: Re: [TCLUG:21970] Should DSL or Cable modem
From: "Thomas T. Veldhouse" <veldy@veldy.net>
Date: Tue, 3 Oct 2000 10:40:15 -0500
References: <Pine.BSI.4.05L.10010031018320.26877-100000@unix1.sihope.com>
He seemed to be talking about changing the lease time in the already
negotiated lease file.  I wasn't aware you could even configure DHCP clients
to ask for a given release interval.  I never saw such an option when
setting up DHCP client.

Tom Veldhouse
veldy@veldy.net

----- Original Message -----
From: "Adam Maloney" <adamm@sihope.com>
To: <tclug-list@mn-linux.org>
Sent: Tuesday, October 03, 2000 10:23 AM
Subject: Re: [TCLUG:21970] Should DSL or Cable modem


> No, if he tells the client to ask for a lease time of 3 weeks, the client
> sends that during the negotiation. The server can reject that lease time
> if it's too long with a NACK followed by another OFFER with a more
> plausible lease time.
>
> Maybe I mis-understood what he said though.  Did he just change the lease
> time in the file that dhcpcd writes with the state information?  That's
> bad.  Really bad.  If he changes the lease time there then the server
> doesn't know about it.  Then you're right, if he sets that to 3 weeks and
> the initial lease was for 2 weeks, then after 2 weeks the server will be
> expecting a renew that it will never get.  It'll assume the client's gone
> and put the IP back into the pool.  If a new subscriber came along they
> could snag up "his" IP legitimately.  Then after a week his client will
> try to renew the IP and the server will NACK it because it's already been
> leased.  Not to mention all the problems he'd have with IP conflicts.
>
> Adam Maloney
> Systems Administrator
> Sihope Communications
>
> On Tue, 3 Oct 2000, Thomas T. Veldhouse wrote:
>
> > Right.  But if he changes the lease time to 3 weeks, but the server is
> > configured for 2 weeks, there may be a 1 week period where two different
> > computers share the same IP address, because somebody else has received
the
> > IP address, and his computer will not ask to renew the old IP address
for
> > another week yet.
> >
> > Tom Veldhouse
> > veldy@veldy.net
> >
> > ----- Original Message -----
> > From: "Adam Maloney" <adamm@sihope.com>
> > To: <tclug-list@mn-linux.org>
> > Sent: Tuesday, October 03, 2000 9:30 AM
> > Subject: Re: [TCLUG:21970] Should DSL or Cable modem
> >
> >
> > > Well if his dhcp client sends a Renew request to the server, the
server
> > > can reject it.  The dhcp client will then just ask for a new IP.  As
long
> > > as he doesn't muck with the client (or bypass it altogether and just
> > > statically configure it) he can't cause any trouble.  The server can
> > > always reject renew requests if the address has already bgeen
reassigned.
> > > I don't think there's anything he can do to the configuration of the
> > > client that could screw anything up, I think he'd have to modify the
> > > source.
> > >
> > > If the IP has already been leased to someone else, and his client asks
for
> > > that IP (in a renew request) the server will send a NACK back, then an
> > > OFFER with a new IP.
> > >
> > > In any case, by changing the lease time you're probably not helping
> > > yourself at all.  As soon as the lease ends your client will send a
renew
> > > request back to the server and you'll get your IP back anyways.  The
lease
> > > time just dictates how long before you have to renew again, but if the
> > > server reboots you may be SOL.  I believe ISC's stores the lease
> > > information in /var somewhere so if the server restarts it'll know who
has
> > > what leased...but I don't know about whatever DHCP server they're
using.
> > > If it's Microsoft's it'll probably explode or something...
> > >
> > > Adam Maloney
> > > Systems Administrator
> > > Sihope Communications
> > >
> > > On Tue, 3 Oct 2000, Thomas T. Veldhouse wrote:
> > >
> > > > Yeah, and that somebody is going to be pissed if they find out that
> > somebdoy
> > > > is using their IP and causing them to have problems with there cable
> > modem.
> > > > Most users are not going to know what the problem is and they are
simply
> > > > going to call MediaOne and complain.  If MediaOne then finds this,
one
> > had
> > > > better watch out, because suddenly the support costs are larger than
the
> > > > profits that they are making off of the trouble causing individual.
> > > >
> > > > Tom Veldhouse
> > > > veldy@veldy.net
> > > >
> > > > ----- Original Message -----
> > > > From: "Adam Maloney" <adamm@sihope.com>
> > > > To: <tclug-list@mn-linux.org>
> > > > Sent: Tuesday, October 03, 2000 9:17 AM
> > > > Subject: Re: [TCLUG:21970] Should DSL or Cable modem
> > > >
> > > >
> > > > > Well if they ran ISC's DHCPd they can set Max-Lease-Time, which is
the
> > > > > maximum amount of time a given address will be leased for.  That's
not
> > to
> > > > > say that when the lease expires you won't renew and get it again,
but
> > if
> > > > > you don't renew right away someone else will probably get it.
> > > > >
> > > > > Adam Maloney
> > > > > Systems Administrator
> > > > > Sihope Communications
> > > > >
> > > > > On Mon, 2 Oct 2000, Eric F Crist wrote:
> > > > >
> > > > > > Trust me, it works.  I've gotten calls from TW and MediaDumb
(aka
> > ATT)
> > > > and
> > > > > > they've not been able to stop it, short of pulling the provision
for
> > > > your MAC
> > > > > > address.
> > > > > >
> > > > > > But, there are ways around that too.  =P
> > > > > >
> > > > > > On Mon, 02 Oct 2000, you wrote:
> > > > > > >
> > > > > > > Thats *only* if the other end accepts such bad things.
> > > > > > >
> > > > > > > AFAIK, you can setup ISC to ignore it.
> > > > > > >
> > > > > > > * Eric F Crist <ecrist@ardent-hacker.net> [001002 21:37]:
> > > > > > > > After a little more research (I had a brain-fart) the file,
on a
> > > > freebsd =
> > > > > > > system
> > > > > > > > is /var/db/dhclient.leases
> > > > > > > >=20
> > > > > > > > This file is realatively simple and straightfoward.  For
> > information
> > > > on y=
> > > > > > > our
> > > > > > > > box, type man dhclient.leases
> > > > > > > >=20
> > > > > > > > If you have questions or comments, feel free to email me.
> > > > > > > >=20
> > > > > > > >=20
> > > > > > > >=20
> > > > > > > > Au Contrair on the static IP.  If you're into the computer
> > hacking
> > > > side of
> > > > > > > > things, you can simply change your lease on the IP to never
> > expire.
> > > > Ther=
> > > > > > > e's a
> > > > > > > > file located on your hard drive that actually sets your
lease.
> > This
> > > > is
> > > > > > > > overwritten at the time of renewal by the DHCP server.  I
have
> > done
> > > > this =
> > > > > > > myself
> > > > > > > > and know others who do it successfully.  Maybe not a legit
> > static
> > > > IP, but=
> > > > > > >  until
> > > > > > > > they find out, who cares?=20
> > > > > > > >=20
> > > > > > > > On Mon, 02 Oct 2000, you wrote:
> > > > > > > > > Disadvantages to cable modem (from my point of view)
> > > > > > > > > - no static IPs, may be coming soon though
> > > > > > > > > - no services on your machine, or you get booted
> > > > > > > > >=20
> > > > > > > > > Advantages to cable modem
> > > > > > > > > - much faster
> > > > > > > > >=20
> > > > > > > > > I got this information from the Time Warner sales rep and
the
> > tech
> > > > rep =
> > > > > > > that
> > > > > > > > > showed up at my apartment complex trying to get
subscribers.
> > > > > > > > >=20
> > > > > > > > > --=20
> > > > > > > > > Jon Schewe | http://eggplant.mtu.net/~jpschewe
> > > > > > > > > For I am convinced that neither death nor life, neither
> > angels=20
> > > > > > > > > nor demons, neither the present nor the future, nor any=20
> > > > > > > > > powers, neither height nor depth, nor anything else in
all=20
> > > > > > > > > creation, will be able to separate us from the love of God
> > that=20
> > > > > > > > > is in Christ Jesus our Lord. - Romans 8:38-39
> > > > > > > > >=20
> > > > > > > > >=20
> > > > > > > >
> > > >
> ---------------------------------------------------------------------
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> > > > > > > > --=20
> > > > > > > > Eric F Crist
> > > > > > > > System Administrator
> > > > > > > > Ardent-Hacker.net
> > > > > > > >=20
> > > > > > >
> > > >
> ---------------------------------------------------------------------
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> > > > > > > >=20
> > > > > > >
> > > > > > > --=20
> > > > > > > Scott Dier <dieman@ringworld.org> #nicnac@efnet=20
> > > > > > > http://www.ringworld.org/  finger:dieman@destiny.ringworld.org
> > > > > > >
> > > > > >
> > > > > > ----------------------------------------
> > > > > > Content-Type: application/pgp-signature; name="unnamed"
> > > > > > Content-Transfer-Encoding: 7bit
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> > > > > >
> > > > > > --
> > > > > > Eric F Crist
> > > > > > System Administrator
> > > > > > Ardent-Hacker.net
> > > > > >
> > > > >
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  - From: Adam Maloney <adamm@sihope.com>
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