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Re: Traceroute was Re: (ASCEND) Bugfixes -- how long does it take?

At 16.10 14/08/97 -0700, you wrote:
>>>   traceroute through my P75 from the internet (ISDN) side returns ***
>>>   (the other way it works just fine).  I'm not using NAT.  Again I told
>>>   them it was of very low priority (to me).  I'd like to know how to 
>>>   reject traceroutes on the P50 at the ISP. I could never figure out how 
>>>   to write the filter so it would work?  Maybe that's another bug???
>>>   I assumed it was just me being dumb.  It's a low priority thing to
>>>   get working.
>>
>>Doesn't traceroute use unpredictable random UDP ports, so that traceroute
>>will automatically fail most of the time if you block all but well known
>>UDP ports, and fail always if you block all UDP ports?
>
>If it does work that way (and that sounds familiar) it would explain why
>I can't get a filter to work at the P50.  It makes the problem at the P75 
>even more baffling.

There are varying methods of writing traceroute. With that said the method
which should work all the time is generating ICMP echo request packets with
the IP header's TTL field set to 1, then 2, then 3, and so on ...

At this point the machine sending the request should be recieving ICMP
error replies indicating Time Exceeded. Eventually the machine should
recieve an echo reply indicating the end point, traceroute completed.

This method uses the Network Layer, therefore no UDP/TCP (Transport layer)
ports come into the equation.

I would attempt to answer the other questions but I don't have my ISDN line
yet so my Pipeline 75 is being used as an expensive paperweight.



;-----------------------------------------------
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  mov     Power,ax    ; plexus at seanet dot com
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