need some networking help!

[James Knott]

Thomas Milne wrote:
> On Tue, May 11, 2010 at 3:41 PM, Jamon Camisso
> <jamon.camisso-H217xnMUJC0sA/PxXw9srA at public.gmane.org>  wrote:
>    
>> On 05/11/2010 12:00 PM, Matt Price wrote:
>>      
>>> Hey folks,
>>>
>>> I'm hoping there's someone out there who can help me with a networking
>>> problem; I kind of doubt the issue is linux-based byt i suppose it's
>>> possible.
>>>
>>> Here's the deal:  I am building an ubuntu-based computer centre in the
>>> basement of a social housing building in Kensington Market.  The
>>> internet here comesi n via dsl to an 8-port router and is farmed out
>>> from there to various computers and I believe a wireless outer
>>> somewhere else in the building. I was hoping to connect a donated hub
>>> (thanks PlanetGeek!) to the router and use the hub to serve out
>>> internet service to the computers in our little cluster,but try as i
>>> might I can't get a dhcp connection to work.
>>>
>>> here's a little more info:
>>>
>>> the hub is a D-link DES-1024R 10/100 switch. there's no serial console
>>> &  nothing in the manual about setting the switch up.
>>> (manual is here:http://www.google.com/url?sa=t&source=web&ct=res&cd=1&ved=0CBIQFjAA&url=ftp%3A%2F%2Fftp.dlink.co.uk%2Fswitches%2Fdes-1016r%2Fdes-1016r_manual_v.02.pdf&ei=V33pS8ytDIP68Aahw9TmDg&usg=AFQjCNG9XxOyyCFBtkqn7JP5wZnVJJtFqA&sig2=EE4ha-MwDs8kkOZCU_Ep6g)
>>>
>>> Attaching a straight-through cat-5 cable from the router to either the
>>> uplink or one of the standard ports, I get solid green on both lights
>>> for that port, indicating an active link.
>>> attaching another cable from one of the other ports to my laptop, i
>>> get two more green lights on that port, again indicating an active
>>> link.
>>>
>>> unfortunately, network-manager fails to connect (this is under ubuntu
>>> lucid, so a recent n-m).
>>>
>>> the same cables work fine for me if i hook my laptop directly into the
>>> hub, so i know that's not the issue.
>>>
>>> logs indicate that i'm getting a dhcp timeout; i've attached a sample
>>> output from /var/log/daemon.log so you cna see what I mean.
>>>
>>> Anyway, if anyone can help i'd be really grateful.  This is a
>>> volunteer project, too -- if you feel like volunteering some time --
>>> or if you think my switch is broken&  you havea  better one -- by all
>>> means let me know!  thanks much,
>>>        
>> Not sure I understand the topology you're describing. In one place you
>> refer to an 8 port router, another hub, and another switch. Technically
>> those are 3 separate pieces of hardware. However, the 8 port router
>> likely combines switch+hub for you so I think your network looks like this?
>>
>>          |
>>        DSL In
>>          |
>>          |
>>    8 port router
>>          |
>>         / \
>>        /   \
>>      WiFi   |
>>             |
>>         DES-1024R
>>
>> So, my suggestion would be to first figure out where clients that do get
>> a DHCP address are receiving it from. Put tcpdump or Wireshark to work
>> on a system that is attached to each of the router/wifi/switch to see
>> how the traffic flows through and is broadcast on the network.
>>
>> Also, to test the functionality of the DES-1024R itself, disconnect it
>> from the uplink and run a DHCP server of your laptop etc. and see if
>> another system on one of the switch's ports receives an IP (again, use
>> Wireshark to capture the traffic).
>>
>> Just some things to try, good luck!
>>
>>      
> I'm pretty sure what he's saying is that he has a hub/switch between
> the router and clients. Nevertheless your advice is accurate, and it
> is confusing to me when he says that "the same cables work fine for me
> if i hook my laptop directly into the
> hub, so i know that's not the issue.". Does that mean he gets
> connected to the 'Net? and without any interaction with the router?
> That makes no sense to me, but it's been awhile, so...
>
>
>    
The simplest thing is to try the router by itself, without any hub or 
switch and then work from there.

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