Recommendation of Tools

Anders Lindbäck list-only at
Thu Dec 4 16:05:53 UTC 2008

On 4 dec 2008, at 14.05, Pekka Savola wrote:

> 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.

According to the 0.75 sorcecode ICMP is still the default prot used,  
and the definition of MTR from bitwizards homepage disagress with you:

"mtr combines the functionality of the 'traceroute' and 'ping'  
programs in a single network diagnostic tool.
As mtr starts, it investigates the network connection between the  
host mtr runs on and a user-specified destination host. After it  
determines the address of each network hop between the machines, it  
sends a sequence ICMP ECHO requests to each one to determine the  
quality of the link to each machine. As it does this, it prints  
running statistics about each machine. For a preview take a look at  
the screenshots."

Even if you use UDP/TCP or whatever, the return packet will be ICMP  
and that will be ratelimited by any carrier worth there salt...

>> 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.

According to the 12.4T refrence it is still set to 1 packet / 500ms  
as default, however changes where made to how you can controll this  
in 12.4(2)T.

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

Anders Lindbäck
anders.lindback at

More information about the NANOG mailing list