dhcpcd question
Joel Hammer
Joel
Mon May 17 11:34:52 PDT 2004
I am sending out dhcp requests from my client machine on eth1 to
comcast. This only seems to happen when I start dhcpcd. The only traffic
I detect after I am connected is incoming, as noted below. That is, the
server is sending a broadcast packet to all clients listening on port 68.
AFAIK, no compliant client rfc2131 listens on port 68, they just use it when
they send out requests. This may be a wrong impression. Anyway, my concern
is that my dhcpcd client just sits there, looking like it is doing
something, but it never talks to the dhcp server at comcast except at
startup. Of course, it may be I am just not detecting the intereaction,
either via dhcpcd builtin logging or with my firewall.
7634 ? S 0:00 /sbin/dhcpcd -d -h tow11dhcp210.towson01.md.comcast.n
Joel
I have just requested my ip number several times. The only message I can get
with tcpdump is:
20:19:23.364117 0.0.0.0.68 > 255.255.255.255.67: xid:0xdea5d34d secs:5 [|bootp]
20:19:23.403762 172.30.10.34 > 68.33.11.210: icmp: echo request (DF)
20:19:23.508113 10.133.184.1.67 > 68.33.11.210.68: xid:0xdea5d34d Y:68.33.11.210 S:172.30.10.35 [|bootp] [tos 0x80]
20:19:23.512957 0.0.0.0.68 > 255.255.255.255.67: xid:0xdea5d34d secs:5 [|bootp]
20:19:23.572200 10.133.184.1.67 > 68.33.11.210.68: xid:0xdea5d34d Y:68.33.11.210 S:172.30.10.35 [|bootp] [tos 0x80]
20:19:23.576663 arp reply 68.33.11.210 is-at 0:e0:29:27:6c:fd (0:2:fc:80:e0:a8)
Of interest, the outgoing packets are not being logged by my firewall, which has the following
rules in the output chain.
0 0 ACCEPT udp ----l- 0xFF 0x00 eth1 0.0.0.0/0 0.0.0.0/0 * -> 67:68
0 0 ACCEPT tcp ----l- 0xFF 0x00 eth1 0.0.0.0/0 0.0.0.0/0 * -> 67:68
So, I guess I have a bunch of questions:
Why no logging is one of them.
Aaagh. But, at least this seems to work, even though I am not understanding
all of it.
Joel
On Sat, Jul 13, 2002 at 07:07:13PM -0400, Matthew Carpenter wrote:
> Doh! Sorry. I lost track of what was going on. Let's get a couple things straight:
>
> I am assuming that eth1 is connected to a cable-modem (layer-2 device) and that the dhcp request is going out from 10.133.184.1, which is your eth1 interface's current IP address. Correct? If not, please explain how IP is set up on your machine, including any addresses you know.
>
> begin "Matthew Carpenter" <matt at e-i-s.cc>
> (Sat, 13 Jul 2002 18:58:27 -0400)
>
> > How are you getting that log message, because your firewall drops it?
> >
> > Use tcpdump to sniff for udp port 67 traffic. See if that's ALL they they are sending. They may be sending the correct traffic as well.
> > tcpdump -i eth1 udp port 67
> >
> >
> > begin "Joel Hammer" <Joel at hammershome.com>
> > (Sat, 13 Jul 2002 18:22:53 -0400)
> >
> > > bootps 67/tcp # BOOTP server
> > > bootpc 68/tcp # BOOTP client
> > >
> > > eth1 is plugged into the comcast network.
> > > I am not running a dhcp server on this machine.
> > > I conclude that the server, broadcasting from its port 67, is broadcasting
> > > to any client listening on port 68. I do no know of any documentation
> > > for a server to do this in RFC 2131. Indeed, I have no processes
> > > listening to port 68. Does comcast have it show dhcpcd software that it
> > > gives its customers to use?
> > > My dhcpcd doesn't log anything except when it stops.
> > > Joel
> > >
> > > On Sat, Jul 13, 2002 at 06:08:38PM -0400, Matthew Carpenter wrote:
> > > > <snip>
> > > > >
> > > > > eth1 PROTO=17 10.133.184.1:67 255.255.255.255:68
> > > > > ( I accept these packets.)
> > > >
> > > > This looks like a server responding to a client. What NIC is plugged into Comcast? Are you running dhcpd on this system as well as dhcpcd? I'm not sure what behavior shit would cause... Would the machine fulfill its own dhcp requests?
> > > >
> > > >
> > > >
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> >
> > --
> > Matthew Carpenter
> > matt at e-i-s.cc http://www.e-i-s.cc/
> >
> > Enterprise Information Systems
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>
> --
> Matthew Carpenter
> matt at e-i-s.cc http://www.e-i-s.cc/
>
> Enterprise Information Systems
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> *Web Development and E-Business
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