This could get educational. ;-) We're both correct. A problem might be too many programs with the same or similar names. Since Margaret manages a Windows network, I presumed she was using TRACERT.exe and not a Traceroute.exe program. Here are the assumptions I'm working with.
Windows TRACERT.exe sends ICMP packets and receives ICMP error messages.
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/wcetcpip/html/cerefTracert.asp
You can use Tracert.exe to send ICMPv6 or ICMP Echo Request
messages to produce command-line report information about
each router that is crossed and the roundtrip time (RTT) for
each hop. By default, tracert queries for both IPv4 and IPv6
addresses, and uses the addresses that the operating system
(OS) returns. You can override this behavior by using the -4
and -6 options.
Linux sends UDP datagrams and receives ICMP error messages.
http://www.die.net/doc/linux/man/man8/traceroute.8.html
This program attempts to trace the route an IP packet would
follow to some internet host by launching UDP probe packets
with a small ttl (time to live) then listening for an ICMP
"time exceeded" reply from a gateway.
And to top it all off, Traceroute programs can use ICMP for sending too, with the appropriate 'switch'.
-----Original Message-----
From: George J. Perkins [mailto:[log in to unmask]]
Sent: Thursday, September 25, 2003 9:56 AM
To: [log in to unmask]
Subject: Re: MSU Internet Access Problems?
On Wed, 24 Sep 2003, Margaret Wilson quoted a personal reply from Don
Bosman to her earlier message, which in turn was based on a suggestion
of mine to use traceroute instead of ping:
> [...]
> ACD has fiber to campus, efectively making them a segment on 'our' network,
> so they should be able to ping the gateway. You should have been able to
> ping via your ACD/MSU account, but not through ACD's own network. Since
> Traceroute uses pings it shouldn't be working from off campus either.
> [...]
Traceroute does not use pings, which are ICMP packets (ECHO_REQUEST sent,
ECHO_RESPONSE returned) by default, it uses UDP packets (on many systems
one can choose, however, to alter the default and send the ICMP "ECHO"
family packets instead). What I forgot in my initial suggestion was that
the responses traceroute listens for are ICMP TIME_EXCEEDED and/or
UNREACHABLE packets (depending on which is appropriate), so even though
the UDP packets it's sending out may get through an ICMP block, the ICMP
packets it's listening for may not.
There are network utilities available which use repeated TCP or UDP
connection attempts in order to simulate pings in an environment where
ICMP is not useful/useable. Many hacker toolkits make use of them
(though actual hackers tend to use other features beyond the simple
"can I get through to system A?" functionality).
-------------------------------------------------------------------------
George J Perkins http://www.pa.msu.edu/people/perkins/
1209B BPS Bldg, MSU Phone: 517-355-9200 ext 2567
East Lansing, MI 48824-2320 FAX: 517-353-4500
