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

To: tclug-list@mn-linux.org
Subject: Re: [TCLUG:21970] Should DSL or Cable modem
From: Eric F Crist <ecrist@ardent-hacker.net>
Date: Tue, 3 Oct 2000 17:49:20 -0500
In-Reply-To: <Pine.BSI.4.05L.10010031018320.26877-100000@unix1.sihope.com>
References: <Pine.BSI.4.05L.10010031018320.26877-100000@unix1.sihope.com>
Wrong, I have a cron to renew everynight, wich tells the DHCP server that my
lease doesn't expire for another x weeks.  The server usually acknowledges this
and simply oks it, without argument.  Since I'm renewing everynight, there's no
reason that someone else would get my IP.  It's all water under the bridge now
anyway, since I have ADSL from UsWorst/Qwestionable at 768K with 8 IPs
(static).  Running servers with a routable network is a lot easier.



On Tue, 03 Oct 2000, you wrote:
> 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
> > > > > > > >
> > > > > ---------------------------------------------------------------------
> > > > > > > > > To unsubscribe, e-mail: tclug-list-unsubscribe@mn-linux.org
> > > > > > > > > For additional commands, e-mail: tclug-list-help@mn-linux.org
> > > > > > > > --=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
> > > > > > Content-Description:
> > > > > > ----------------------------------------
> > > > > >
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> > > > > > Content-Description:
> > > > > > ----------------------------------------
> > > > > >
> > > > > > --
> > > > > > Eric F Crist
> > > > > > System Administrator
> > > > > > Ardent-Hacker.net
> > > > > >
> > > > >
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> > 
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> 
> 
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-- 
Eric F Crist
System Administrator
Ardent-Hacker.net
Follow-Ups:
- Re: [TCLUG:21970] Should DSL or Cable modem
  - From: "Thomas T. Veldhouse" <veldy@veldy.net>
References:
- Re: [TCLUG:21970] Should DSL or Cable modem
  - From: Adam Maloney <adamm@sihope.com>
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