Network interface failure detection

[Robert G. Brown]

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
away?

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
/var/log/boot.log.

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