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Date:      Wed, 5 Jun 2002 19:31:19 -0400
From:      "C J Michaels" <cjm2@earthling.net>
To:        <barbish@a1poweruser.com>, "Samuel Chow" <samuelc@samuelstn.dhs.org>
Cc:        "FBSDQ" <questions@freebsd.org>
Subject:   RE: dhcp client and cable modem
Message-ID:  <CDEJIONOMGKHCNHBALKPCENDCAAA.cjm2@earthling.net>
In-Reply-To: <MIEPLLIBMLEEABPDBIEGMEAFCCAA.barbish@a1poweruser.com>

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> -----Original Message-----
> From: owner-freebsd-questions@FreeBSD.ORG
> [mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Joe & Fhe Barbish
> Sent: Wednesday, June 05, 2002 11:36 AM
>
>  Samuel wrote
> Are you saying your dhclient cannot get an IP address because
> of ipfw?
>
> I reply
> No
> I am just trying to determine what some the default deny all
> packets belong
> to.
> Since I just started using dhclient, it was something to check out.
>
> I have these rules
> # Special rules for Adelphia Cable access
> $cmd 00174 allow udp from me 68 to $odns1 67 out via rl0
> $cmd 00175 allow udp from $odns1 67 to me 68 in via rl0
> $cmd 00176 allow udp from any 67,68 to 255.255.255.255 67,68 in via rl0
>
> I do not understand why dhcp is talking to my ISP's DNS server or

DNS server?  Oh.. it is probably trying to dynamically update the zone w/
your new ip.  It's a newer feature of isc v3.

> why  it's using  255.255.255.255 for an ip address.

Default 'broadcast to the whole world' address.  No matter what your IP,
subnet, network id.  You will always listen to a req that comes in on
255.255.255.255.  This is necessary for dhcp to work since many times at the
inital req you don't actually have an ip/network id/etc...

--Chris

>
> Is this normal?

Yes

>
> Your example of
>     # Allow DHCP packets in and out
>     3200 add pass udp from any 68 to any 67 out via xl0
>     3200 add pass udp from any 67 to any 68 in via xl0
>
> is just way to wide open for my liking.
>
>
> Let me know what you think
> Joe
>
>
>
> -----Original Message-----
> From: owner-freebsd-questions@FreeBSD.ORG
> [mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Samuel Chow
> Sent: Wednesday, June 05, 2002 11:07 AM
> To: barbish@a1poweruser.com
> Cc: FBSDQ
> Subject: Re: dhcp client and cable modem
>
>
> > I'm using the FBSD built in dhcp client on the Nic card to the cable
> modem.
> > My ipfw firewall is denying a bunch of packets which never happened
> > with the modem connection.
> >
> > Could somebody tell me what ipfw rules I need to allow the cable isp
> > dhcp server to correspond with my FBSD gateway?
>
>     Are you saying your dhclient cannot get an IP address because
>     of ipfw?  If so, try the following rules (of course, replace
>     rule number and interface):
>
>     # Allow DHCP packets in and out
>     3200 add pass udp from any 68 to any 67 out via xl0
>     3200 add pass udp from any 67 to any 68 in via xl0
>
>     Hope this helps.
>
> ---
> Samuel Chow
> samuelc@samuelstn.dhs.org
>
> This message is displayed using recycled electrons.
> Segmentation Fault (core dumped)


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