Re: Network going up and down...

On Fri, 14 Mar 2003, System wrote:

> No i am trying to connect it through thr ip only and it connects but the
> connections remains for sometime and then i get lost:(
> I don't know why its up for sometime and then down for another restart.
> 
> Where can i find the log for this:()

Nowhere, most likely.  First, while every event that happens with an OS 
could be logged in very few cases is doing so a good idea.  Second, many 
events are outside the control and/or knowledge of the OS.  What you 
are describing sounds like it is a hardware or network issue, not an 
OS issue.  In these cases the OS cannot log anything as it has no 
knowledge of what has happened.   The one place in the OS that could be an 
issue is the NIC driver.  What version of the kernel, what NIC, what 
driver? Are there any messages about missed interrupts by the NIC, buffer
overruns, etc. in /var/log/messages?

You contend in a prior message that there is no IP address conflict; that
alleviates one network issue.  Is there a routing issue?  Do you have
asymmetric routes?  Is this straight telnet or is it telnet via some
tunneling protocol?  Is there a hardware issue with the NIC?  PCI bus?
Bad cable?  Bad switch/hub port?  I would start by looking at the easiest
to control/fix.  If it is a managed hub/switch, look at the device logs
and see how many errors/bad packets etc. occur as a percentage of bytes or 
packets transferred?  Is is abnormally high?  If you do not have a managed
device, try a different switch/hub port or a different switch/hub 
entirely.  Try a different cable connecting the machine to the switch/hub
(better to test the cable if you have a REAL cable tester, not one of 
those $20 cheapies that only ensure that an applied current can travel
end to end).  Switch to a different NIC, even better if it uses a 
different driver.

Lots of things to try.  No one will be able to help you narrow it down 
more unless you post more specifics, things like NIC mfr and model, kernel 
version, driver, driver version, etc.  For network issues, traceroute
output is useful, even better if you have traces from both ends (can show 
if you have asymmetric routes).  

- rick -