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Re: problem with switch



On Sun, 6 Aug 2006, Andrew Sackville-West wrote:


On Sun, Aug 06, 2006 at 02:33:35PM -0400, Faheem Mitha wrote:


Hello everyone,

I've recently encountered an odd problem with a switch and a Dell PC
running Debian. I'm using it on a cable modem. When I plug the machine
directly into the cable modem, I can get on the net (the cable modem
uses DHCP as per usual).


if you can get a dhcp lease directly from your cable modem, then dhcp
client is working on the debian box.



However, when I plug the machine into the switch, the machine can't
get on the net, in fact it can't get a lease from the DHCP server at
all.


does the switch have an incorporated router?
Not certain, but don't think so. It is a fairly generic Netgear switch, which I picked up at Best Buy. Routers and switches are separate things, aren't they? 


does it supply dhcp service? is that dhcp service turned on?


Don't know to both.
does it have some sort of configuration that might be preventing you from getting a lease? 

Don't know, but if so wonder how the laptop below is getting a lease.
Presumably it is possible to access the switch configuration and see what is going on. 


However, a Mac OS X laptop does not have any problems. Therefore, the
problem presumably has something to do with the combination of the
switch and the machine.


is the laptop connecting by wire or wireless? if wireless, you're
dealing with different systems... If wired, how does the osx box get
ip? is it set for fixed IP? are you saying that the osx box gets a
dhcp lease from the switch(router?)?
Sorry, I should have been more precise. Yes, the laptop is also connecting via ethernet through the switch (exactly the same configuration as the Dell PC), and it is also using DHCP, but from the dhcp server of the cable isp (I think). I really doubt it is getting it from the switch, because it is certainly a valid IP address.
This is what makes this so puzzling, since at least at first glance this seems to point to some problem with the Dell PC rather than the network. 


The machine in question has a Broadcom card, and is using Debian's
somewhat hacked around with tg3 driver, so I'm wondering if that could
perhaps be causing the problem, and if so, whether switching to the
bcm5700 would solve it.



I can't imagine that if it works direct connected to the modem that it
won't work through a switch. there is something else wrong in your
network, would be my guess. try setting a static ip on the debian box
and see if that works.
Unfortunately I don't have a static IP address to use, at least not on that cable service.
Thanks for your helpful suggestions. I now have some more pointers for trouble-shooting. 

                                                                Faheem.
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