ping questions

Karl Auer kauer at biplane.com.au
Tue Dec 22 14:49:24 UTC 2015


On Tue, 2015-12-22 at 08:44 -0500, Gene Heskett wrote:
> To me, the term "private network" means its behind a router doing a NAT.  
> If the NAT is to a 192.168,x,y address, no router I am aware of will 
> allow that to pass UNLESS that "port" is forwarded to a machine behind 
> the router in which case that machine is free to respond or not 
> according to how it is configured.

He may "think" he has a network - hence my question about other devices.

The setup you describe is certainly typical, but it's also certainly not
the only possible setup. Since his setup is behaving unusually, and
since the pings only work when his PC is active, it seems reasonable to
theorise that it may be his PC that has his ISP-supplied static IP
address, and not the device he calls a "modem".

If that static IP of his is on one of his PC's interfaces - and
especially if that interface is a ppp interface - then that's almost
certainly what's going on, and to get a "private network" he will need
to put a router and a switch (or a combined device) between his modem
and his network.

You are right about the router - if it is one - not passing pings
through NAT. It is very unlikely that pings are being passed through to
the PC unless someone made a specific effort to configure the device do
do that. It's even less likely that someone would not remember doing it
nor know what he/she was doing when they did it. Further evidence for
the theory that it is not a router (or at least, is not routing).

It's a bit before 5pm in Switzerland right now - my guess is we will
know more after the OP gets home :-)

Regards, K.


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