[NTLUG:Discuss] Troubleshooting when you lose the Internet (2 questions)

[Wayne Dahl]

On Sat, 2003-02-22 at 13:47, Jack Snodgrass wrote:
> On Sat, 2003-02-22 at 13:15, Rick Matthews wrote:
> > Everybody knows that "stuff happens" on the net.  I'll click a link 
> > from a search engine and it will be slow (or dead).  No big deal.
> > I may click another link and find it in the same shape.  Depending 
> > on what I am doing at the time, it may take several bad clicks before
> > my brain snaps to and realizes that it may not be the links.  I'll 
> > click on a "known good" site, and if that is unsuccessful I'll 
> > try another.  But when my email client then tells me that it is 
> > unable to contact my external pop3 server, I'm sure there is a problem.
> > Now what do I do?
> > 
> > My ADSL is connected to eth0 in my Linux firewall box; eth1 connects
> > to a LinkSys switch and then to Windows boxes.  The Linux box also 
> > runs Squid, squidGuard, and Apache (internal only, serves reports, 
> > docs, and squidGuard redirect pages).
> 
> 
> Generally, when you 'reboot and network things start working again', 
> it's a DHCP problem. You might be able to accomplish the same 
> results without rebooting by doing a /etc/rc.d/init.d/network restart
> ( on redhat anyway. Your distribution should have a similar command
> line call to tell your networking to stop and restart. ) You don't
> need to do a full reboot just to restart your network. 
> 
> A even less drastic approach ( you may loose some network 
> connections if you restart your network in the middle of a file 
> transfer or other type of network link ) would be to send a SIGHUP
> to your dhcp client process. This will tell the client to renew 
> it's IP Address. The process for doing this depends on your 
> dhcp client. 
> 
> Other things you can do to debug this is to run traceroute ( or 
> mtr - a better replacement ) to different addresses ( your ISP 
> and / or favorite sites ) and see what happens with that. It's 
> generally a good idea to do this when things work ( and maybe
> print off the results ) and do this when things don't work. 
> You might see if it's you, your isp or your isp's isp that
> is having the problem. 
> 
> jack
I have had this problem as well.  I'm connected via ADSL on a Fujitsu
modem with a LinkSys 4 port DSL router.  When I lose a connection, all
computers on my network also lose their connections.  Past experience
has taught me that what I have to do to get a reconnection is to power
down the modem (do a hard reset) and reset the router.  When they come
back up, I have my connections on all computers again.  

I've tried just rebooting the modem, no go.  I've tried just rebooting
the router, also no go.  What it seems to take is a reboot of both.  It
appears that the modem and router seem to lose sync and by rebooting
both, a resync is forced.  I've tried to theorize why this happens, but
so far I've got nothing.  It can happen when the network is idle for
long periods of time (I could possibly see a long string of zeroes
causing a lost sync condition...I'm not sure what sync scheme ADSL uses,
ala AMI or B8ZS as a T1 would use) or it can happen while the network is
being used.

I've brought this up with VASG (Verizon Advanced Services Group, their
ADSL tech support group...I work with them all the time at work) and one
guy suggesting setting the routed to emit a keep-alive every 60 seconds
or so and when I tried that, the network lost all connection to the
Internet.  I had to switch it back to dial-on-demand, go dead after 5
minutes if no activity.

Any one else having this same problem and were you able to resolve it? 
If so, what did you do?

Wayne