ping questions

Colin Law clanlaw at gmail.com
Tue Dec 22 15:29:47 UTC 2015


On 22 December 2015 at 14:56, Karl Auer <kauer at biplane.com.au> wrote:
> On Tue, 2015-12-22 at 14:35 +0000, Colin Law wrote:
>> What does traceroute show from inside the network and outside.
>
> If ping doesn't work from outside, then traceroute won't work. Some
> traceroutes can use UDP and TCP probes, but they won't work either
> unless they are specifically enabled in the "modem".

Traceroute will show how far it gets.  For example, when I run, from
inside my network
traceroute <my external ip address>
I see
traceroute to nnn.nnn.nnn.nnn, 30 hops max, 60 byte packets
 1  <my ip>.dyn.plus.net1   5.160 ms  5.449 ms  5.750 ms

So the router is replying directly even when pinged from inside.
However when I do it from outside I see a list which starts ok and
ends up with
 6  link-a-central10.ptn-ag04.plus.net (212.159.2.141)  49.448 ms
49.433 ms  49.401 ms
 7  * * *
 8  * * *
 9  * * *
10  * * *
11  * * *
...
Which says to me that my ISP (plusnet) is blocking ping.  So I see
exactly the same issue as the OP.


>
>> Also have you forwarded the port in the modem?
>
> Pings don't have ports. Which ports do you mean?

Ignore that, I was spouting rubbish, as is often the case.

Colin



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