internet blocking problem ?

Jay Jaeger cube1 at
Fri Sep 11 12:44:12 CDT 2015

On 9/11/2015 11:58 AM, Noel Chiappa wrote:
>     > From: Jon Elson
>     > so MANY others who could not access the page were finding
>     > they got stopped at cogentco.
>                ^^^^^^^^^^^^^^^^^^^
> Well, to be precise 'Cogentco was the last node on the route which
> responded'.
> It's impossible to say whether i) that node tossed packets that tried to go
> further; ii) it forwarded them to some other node (identity unknown) which
> did toss them (and didn't allow/handle traceroute), etc.

Strictly true.  However if Cogent were blocking them, they would most
likely block them at *ingress* rather than egress - more efficient.  My
guess is that it is the next node - the first unidentified node - that
is doing the blocking.

> One can't draw any conclusions about whether it's i) from the fact that it's
> _also_ still responding to traceroute packets sent to that address: one would
> have to know whether it does the a) 'is this packet to a destination I'm
> filtering' check before it does the b) 'I decremented the TTL and it's now
> zero', or the other way around. If b) it could be the node that's dropping
> the packets.
> But given that other 'last hops' are also producing similar results, I'm
> still thinking it's which is tossing the packets, not the 'last hop'
> one can see on traceroutes.

I expect that is correct.


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