[NCLUG] Perplexing wireless issue - Voodoo accepted

[Paul Hummer]

On Sun, 07 Feb 2010 21:04:36 -0800
Matt Taggart <matt at lackof.org> wrote:

> >  My other devices were working fine on the network
> > (PS3, Xbox, other laptops/desktops).
> 
> Are any of these devices wireless? Or are they wired on the WRT54GL ports 
> or elsewhere on the network?
> 

The only devices actually plugged into wired ethernet on the router are the
network printer and the media server.  Everything else (including the PS3 and
Xbox) are all wireless.

> It would help to determine:
> * If any other wireless devices are getting DHCP and working.

Wireless devices get DHCP fine.

> * If any other wired devices on the WRT54GL are getting DHCP and working.

Wired devices are getting DHCP fine.

> 
> Then you can determine if the problem is just the laptop, just the router, 
> just Tomato, or some combination.

I think it's specifically between the laptop's wireless and the router's
wireless.  I can plug into the router directly with this laptop and everything
is fine.

> 
> > I then hooked up another router through the WRT54GL (a
> > Buffalo WHR-HP-G54 with dd-wrt) and then laptop connected right up.
> 
> You connected the buffalo to one of the client ports on the WRT54GL and 
> then the laptop was able to get a wireless link to the buffalo? And it got 
> an address via DHCP? from the buffalo or from the wrt?
> 

The Buffalo router was hooked into the peer ports of the router, behind NAT.
It got an IP fine.  I connected to the Buffalo router via wireless and got an
IP address just fine.

> So far I think the problem is either the laptop or the wrt hardware itself, 
> but answers to the above might narrow it down some more.
> 
> >   The logs on the laptop indicate that it sends the DHCPREQUEST but
> > receives no DHCPOFFER.  The logs on the router indicate a DHCPOFFER was
> > sent, but no DHCPACK is received. I tried using wireshark and tcpdump
> > to see if the laptop was just ignoring the DHCPOFFER packet.  I couldn't
> > get anything conclusive, but maybe my flags were wrong, or I wasn't
> > looking close enough.
> 
> Here's another total stab in the dark, but since your symptoms match those 
> of a problem I once had I thought I'd mention it...
> 
> Make sure Explicit Congestion Notfication is turned off on the laptop.
> 
> cat /proc/sys/net/ipv4/tcp_ecn
> 
> should return zero. If you are using a distro kernel then it should be off 
> already, but if you built your own maybe you thought this sounded like a 
> nice feature and turned it on (like I did when I ran into a similar 
> problem).

I'm using Karmic, and this returned 2.  I have no idea what that means, but
there weren't any changes on the laptop or the router between the times that it
was working and when it wasn't (no one was even home, and the dog doesn't
usually surf the net while I'm gone).

Cheers,
Paul

> 

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 835 bytes
Desc: not available
URL: <http://lists.nclug.org/pipermail/nclug/attachments/20100207/6779db14/attachment.pgp>