[97595] in RedHat Linux List
Re: DHCP accross router??
daemon@ATHENA.MIT.EDU (William Stearns)
Tue Nov 3 23:42:58 1998
Date: Tue, 3 Nov 1998 23:45:35 -0500 (EST)
From: William Stearns <wstearns@pobox.com>
To: Josh Kuperman <sar_kuper@sals.edu>
cc: ML-redhat <redhat-list@redhat.com>
In-Reply-To: <3.0.5.32.19981103160721.008089b0@mailx.netheaven.com>
Resent-From: redhat-list@redhat.com
Reply-To: redhat-list@redhat.com
On Tue, 3 Nov 1998, Josh Kuperman wrote:
> I feel like I must be an annoyance to you by now, but I can't get this
> stuff to work at all.
Hey, we're in the same boat. No matter how you slice it, Linux is
complex. I'm sincerely happy to help where I can as my way of indirectly
paying off my debt to the people who've helped me.
> I did as you suggested also looked at various web sites and downloaded, but
> did not install newer versions. I also managed to try to test things on the
> machine I thought I had previously configured to use DHCP, so now that one
> doesn't work with or without DHCP.
>
> I did a clean install and made a modular kernel. (I haven't enabled kernel
> hacking yet, perhaps I will need to.) I was using the PowerTools 5.1 CD set
> which had drivers from last April, so I just went with what was on the CDs.
You shouldn't have to enable kernel hacking. The PowerTools code
should be just fine.
> Everything was pretty much the same. Depending on when I added the route
> and when I ran tcpdump I would get different results.
>
> I managed to run tcpdump immediately after starting the network start
> script. The output was
>
> 0.0.0.0.68 > 255.255.255.255.67 cdhp 548
Was this on a different machine on your network? If so, great,
the request packet actually left your nic. If the tcpdump was on the same
machine, the packets probably left (I'm just not sure if there's some
obscure case we might be rnning into).
Either way, we're partway there!
> repeated a few times and then nada. BTW I didn't pipe it to egrep, there is
> either very little noise on the network or there is something keeping
> things from showing up. I've decided I've no idea if any of my networking
> components are at all functional in Linux from the NIC to software.
Make sure you run tcpdump as root, otherwise you can't put the nic
into promiscuous mode and see all packets on the lan.
Has this card worked under Linux before?
Here's a quick test. Find two W95 machines and write down the IP
address of one, all the Ip info from the other and shut this one
completely off. Enter that info into
/etc/sysconfig/network-scripts/ifcfg-eth0 on you Linux box. Run
/etc/rc.d/init.d/network stop
/etc/rc.d/init.d/network start . Can you ping the box that's still up?
If so, you've got a working network card. If not, check that the hardware
info reported by ifconfig matches how you have the network card set up bu
jumper or software:
eth0 Link encap:Ethernet HWaddr 08:00:5A:CA:61:F9
inet addr:172.16.0.253 Bcast:172.16.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:106 errors:0 dropped:0 overruns:0
TX packets:0 errors:11606 dropped:87 overruns:1
Interrupt:3 Base address:0x300 Memory:c00d4000-c00d8000
^ ^^^^^ ^^^^^^^^^^^^^^^^^
If that's OK, go back to CMOS setup and check PCI configuration.
If you're using an ISA card in ISA mode, make sure that the card's
interrupt is set to ISA mode. If you're using either an ISA Plug and play
card or a PCI card, make sure that the interrupt is set to PCI/PnP.
> I downloaded a newer version of DHCP from the isc web site and apparently
> adding the all-ones host is still required. I reviewed the docs, but I
> believe I'm still missing something.
>
> If you have a good suggestion as to how to make sure component pieces are
> working and properly attached that might help. Yes, everything works from
> the Wintel world, but I could be missing something very basic in a *.conf
> file or a strartup script.
The goal here is to see exactly how far the communication gets.
The conversation normally consists of 4 packets. 1) Client
machine sends out a broadcast packet to the dhcp/bootp server port: can
anyone give me an IP address? 2) dhcp/bootp server replies and says use
this address, gateway, dns server, etc. 3) Client says, OK I'll use it,
thanks. 4) Server replies OK. So far you've sniffed out numer 1.
Check the following.
1) Try the test once more with tcpdump on a different machine (If
you see the request, the request is getting onto your lan). Make sure you
run tcpdump as root..
2) See if the person that administers the dhcp machine is willing
to help; ask him to watch his/her logs while you try again. Are they
getting a dhcp request from the bootp relay on your network at all? Are
they getting an error that means their dhcp/bootp server isn't returning a
reply or do they think it _is_ returning a reply? Can they use tcpdump or
some other sniffer on their lan segment and see the response returning?
Does it have a destination address of the nic on their side of the bootp
relay? Can they verify that they are, in fact, using a bootp relay?
Repeat the above with a W95 workstation making the request. What
happens differently with tcpdump and with their logs?
3) Take a look at any configuration files for the dhcpcd you're
using. Is it possible to specify the IP address of the dhcp server? If
so, try setting it manually instead of leaving it at the 255.255.255.255.
Winipcfg in W95 will tell you the Ip address of the dhcp server.
4) Just for grins, try the following; try setting your default
route to be the IP address of the dhcp relay. I honestly don't know if
it'll help, but it might be instructive/useful... For example:
route -n del default
route add default gw ip_of_bootp_relay dev eth0
Sorry for the disorganized thoughts; it's getting a little late
here.
If you're willing to try some more, I'm willing to help. Please
keep me posted.
Cheers,
- Bill
>
>
> At 04:59 PM 10/29/98 -0500, you wrote:
> >On Thu, 29 Oct 1998, Josh Kuperman wrote:
> >
> >> This gets weirder and weirder. The router lets bootp work accross the
> >> router as well so I'm pretty sure the message is getting through to the
> >> DCHP server. I tried repeatedly to change the configs and restart the
> >> networking. The DHCP server is on a Dec Alpha VAX. I tried to run
> >> /sbin/dhcpcd with numerous options including -r, but the result was always
> >> the same. I would get a message to the log that said
> >>
> >> no DHCPOFFER
> >>
> >> and then it would die. The only option I can imagine is something to do
> >> with the Identification. I don't know how the machine identifies itself to
> >> the server in Windows 95.
> >
> > Oh, darn! I'm not sure if you need it, but try running this line
> >from the command line as root:
> >
> >/sbin/route add -host 255.255.255.255 eth0<Enter>
> >
> > This tells your machine where to send the DHCP request;
> >specifically, it dumps it out to the Ethernet lan. I suspect that your
> >linux box didn't know where to send the request - it's a networking nit
> >that hasn't been gracefully resolved yet.
> > Then try those commands again. To see if the packets are actually
> >leaving your machine and if any responses arrive back, try:
> >
> >tcpdump -i eth0 -qltn | egrep '(\.68|\.67)'<Enter>
> >
> >(briefly, show me all the packets on eth0, but only show ones with either
> >".67" (bootp/dhcp server port) or ".68" (bootp/dhcp client port)).
> >
> > If this attempt doesn't work, mail me the output from the above
> >and I'll see what I can do.
> > Cheers,
> > - Bill
> >
> >[original message snipped]
---------------------------------------------------------------------------
Unix _is_ user friendly. It's just very selective about who its friends
are. And sometimes even best friends have fights.
William Stearns (wstearns@pobox.com)
Mason, buildkernel, and named2hosts are at: http://www.pobox.com/~wstearns
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