In message <199512022318.RAA29277@solutions.solon.com>you write:
> Is there a way to determine whether an interface is idle?  Some of our
> users occasionally line camp.  Unfortunately, since the tty is idle during
> an entire PPP or SLIP session, we can't just check for idle time.  :(

Try slstats or pppstats.  It might do the trick for your intent.

You can also use netstat -i -I<interface> -w<waitinterval>

Gruesse
       Oskar

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