[H-GEN] Re: intermittent cable connxn outage

Troy Piggins troy at piggo.com
Wed Dec 8 01:19:31 EST 2004


Sorry for such a long post.  I am happy to email direct to someone
if the whole list doesn't want to  know about it.

* Russell Stuart <russell-humbug at stuart.id.au> :
> On Tue, 2004-12-07 at 16:40, Troy Piggins wrote:
> > The problem is that just yesterday and today the connection to
> > internet is only working intermittently.  By this I mean that it works
> > for hour or so, then can't see anything outside (ping, DNS etc), then 
> > it works for a while, then not.
> 
> If you have changed nothing, the most likely explanation
> is the rain.  Raid plays havoc with telephone lines.

Hmm, it is cable broadband.  Don't know if that would be affected.
Telstra camne out a lunchtime to check the hardware.
They can see the modem from their end (it's MAC anyway), but when
they ping it they were averaging 20% packet losses.
They changed the modem to a new one (same model).  When they plugged
it into laptop (WinXP) it worked fine.  But that was only for a
short period.

When I plugged the new modem into the linux box, it worked again for
a short while (long enough for them to say it's working and leave).
Then it stopped again.  I am going to try another network card.

> > Another thought was that it could be hardware - network card playing
> > up, or even the modem?  I don't know how to check this.  I don't have a
> > spare modem.
> 
> You don't say what modem is telling you when the problem strikes.
> What are its lights doing?  Its lights may be saying "we have a problem
> here - I can't get sync".  If they are you can toss the problem
> back to ISP as the box (windows / linux) doesn't come into it.
> (I presume you can at least connect to the modem's web page.)

All lights (online, power, send, receive) are steady green, and the
transmit orange light is blinking the same as it does when data is
transferred.  All looks normal.

Modem's web page?  I haven't tried that.  I assume you mean the http
interface to the modem.  Don't even know if it has one. Will try.

The IP of modem 192.168.100.1, and does not work when internet down.
Will have to try when internet is up.

> > Could be a DOS attack?
> 
> Anything is possible I guess.  Install iptraf and have a look.

Hey, I like that iptraf!  Never used before.

When the internet connxn is working, the packets in and out look ok
(to me).  When it is not working, iptraf outputs lines like this a
lot :

ICMP dest unrch (host) (90 bytes) from 147.10.92.105 to 147.10.92.105 on lo
UDP (366 bytes) from 10.203.80.1:67 to 255.255.255.255:68 on eth0

over and over.  I have not included the internal interface's output.

and all TCP traffic stops.

> > I can't ping IP address or URLs (when it is not working).  When it
> > works DNS resolution etc is fine.  I spoke to ISP and they don't know 
> > of any problems in the area.  Oh, and as soon as I mention the gateway 
> > is linux, they say "we don't support linux, windows only" and 
> > conversation ends shortly after :-(
> 
> You are often on your own when it comes to Linux.  

I am not on my own - I have you guys :-)

> But just
> about everybody has a windows box on hand - especially in an
> office.  It should be very easy to move the modem to a
> windows box for the exercise.  

True.  I will try that on the weekend if not resolved by then.

> I presume powering the modem
> off and on doesn't fix anything.

Correct.

-- 
T R O Y  P I G G I N S
e : troy at piggo.com




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