Recommendation of Tools

Pekka Savola pekkas at netcore.fi
Thu Dec 4 07:05:50 CST 2008


On Wed, 3 Dec 2008, Anders Lindbäck wrote:
> Mtr is even less usefull then that, in its default mode it does a traceroute 
> and then proceeds to ICMP Ping flood each IP in the list generated by the 
> traceroute, the result is usually completly useless on WAN topologies due to 
> asym-routing, ICMP node protections by carriers and punting etc..

No, it doesn't try pinging the routers in the middle, at least not 
anymore (I just re-checked with 0.71 and 0.75).  I vaguely recall 
behaviour like that in the past, however, so it's possible that long 
time ago mtr did behave that way.

> And using UDP will not really provide better results due to the same thing, 
> and IIRC Cisco from 12.0 has a standard setting of no more then 1 ICMP 
> Unreach per 500ms..

This is true and the point I was getting at, though I believe the 
bucket is much larger in any recent software release (also in 12.0 
series).  Actually, 5 years ago, you could see spot Cisco routers in 
"traceroute6" because they dropped the rate-limiter didn't respond to 
the middle packet and it resulted in a star.  The rate-limiter has 
long since been fixed to be more lenient.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings


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