Network interface failure detection

Robert G. Brown rgb at
Sat Mar 16 14:30:33 EST 2002

On Fri, 15 Mar 2002, lakshmi wrote:

> Hi,
> Does anybody know about a means by which 
> it can be found out whether a network 
> interface card has failed or somebody has
> pulled out the ethernet cable?
> For example, there is a routing socket API
> using which it can be found if a route was
> added or not. 
> Similarly will the IP layer or the data link
> layer report some sort of an indication of
> the ethernet card fails? Is it possible to
> detect at the IP layer or at the data link
> layer if the ethernet cable was pulled out?

What exactly do you mean?  Or where?  On the host in question?  From far

There are lots of tools on the running system.  netstat, ifconfig,
route.  There are lots of places on the running system.  /proc/net/dev,
/var/log/messages and or dmesg (file or output of command), and

There is the physical interface -- most NICs and switches have link
lights (so you can "check the cabling" in a sense).

>From far away though, there is a bit of a catch 22.  Has the interface
failed, or the route, or is the system too loaded to answer?  Has the
system crashed?  Hard to tell.  traceroute might help you detect routing
problems per se, or might not.  ping can be useful as well.  However, it
is >>really hard<< to detect a remote network interface failure per se
-- there are multiple possible causes to a failure in communications,
and any one of them might appear to be a "dead" socket.

If you were really asking for the names of tools like route, ifconfig
and so forth I'd recommend that you consider buying a good book on Unix
or Linux systems administration, since most of them are described in
detail therein.


> Thanks.
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Robert G. Brown	             
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at

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