Re: easy way to scan for issues with path mtu discovery?

[Justin Shore <justin () justinshore com>]

Darden, Patrick S. wrote:
> Hi all,
>
> Does anyone know of an easy way to scan for issues with path mtu discovery along a hop path?  E.g. if you think someone 
> is ICMP black-holing along a route, or even on the endpoint host, could you use some obscure nmap flag to find out for 
> sure, and also to identify the offending hop/router/host?  What tool would you use to test for this, and how would you 
> do such a test?  Is there any probing tool that does checks like this automatically?
>
> Seems to me this happens often enough that someone has probably already figured it out, so I am trying not to reinvent 
> the wheel.  All I can think of would be to handcraft packets of steadily increasing sizes and look for replies from 
> each hop on the route (which would be laborious at best).  Google has not been kind to my researches so far.

Take a look at tracepath.

http://www.google.com/search?hl=en&q=tracepath&btnG=Google+Search

I haven't done much of anything with it but it may be of use to you.

Justin