I specifically blocked ICMP type 8 which is the echo request, all other ICMP packets flow, and I tested from a Win XP box both tracert (win version) and ping, received the desired results (worked fine and destination unreachable respectively).
It sounds like ICMP type 8 isn't being dropped.
tracert (Windows version) uses ICMP type 8 (same as ping); the difference is that tracert varies the TTL of each packet (so they come back before they reach the destination.
For ping, if the packet is dropped, you should see "Request timed out". The "Destination unreachable" means that the ICMP type 8 packet went out, and a "Destination unreachable" packet came back, indicating that the packets aren't being dropped.
Using MTR (Matt's Traceroute) from a NetBSD box on my network packet loss within the LAN went from
65-75% to 6%.
That is very strange. I can't explain why that would happen, unless ICMP type 8 was being dropped, but it doesn't seem to be.
MTR uses traceroute to determine the path, then pings each hop in succession to get statistics for each hop. Interesting that ping and traceroute are implemented with different protocols, I thought they only used different ICMP packet types.
Ping and tracert (Windows version) both use ICMP type 8 packets (ping sends a packet with a high TTL so it will reach the destination; tracert sends increasing TTLs with each packet to see where each hop is). Traceroute (Unix version) uses UDP packets (typically on ports over 30,000).
-Scott
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