[clug] Re: Determining availability of a remote machine
Jepri
jepri at webone.com.au
Wed Apr 2 17:47:30 EST 2003
On 2003.04.02 17:43, Steve Jenkin wrote:
> 'traceroute' relies on the proper intermediate handling of expired
> 'time to
> live', not ICMP ECHO (ping).
>
> >From my (linux) manpage:
> -I Use ICMP ECHO instead of UDP datagrams.
>
> -p Set the base UDP port number used in probes
> (default is 33434). Traceroute hopes that nothing
> is listening on UDP ports base to base + nhops - 1
> at the destination host (so an ICMP PORT_UNREACH
> ABLE message will be returned to terminate the
> route tracing). If something is listening on a
> port in the default range, this option can be used
> to pick an unused port range
>
> ... .then listening for an ICMP "time exceeded" reply from a
> gateway.
>
> --
> Would be nice if it would use an designated TCP port, would work just
> as well
> and could be 'jiggled' to go through various firewalls. [tcp:80/http
> is an
> obvious default choice]
This is already part of the ping standard. Try looking in your
/etc/services file. It's almost always commented out.
More information about the linux
mailing list