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Re: Is there a way to know the ISP with the default installation of Stretch?

On Tue 02 Jan 2018 at 11:15:16 (-0500), Greg Wooledge wrote:
> On Tue, Jan 02, 2018 at 04:03:46PM -0000, Dan Purgert wrote:
> > Max Power wrote:
> > > My problem is to know the ISP [e.g. GATEWAY = Vodafone, Telecom or AT&T]
> > > before starting browsing or any remote connection...
> > 
> > Checking the hostname of an RFC1918 address will nearly never provide
> > you with an ISP's name, even if you do it on a residential-gateway
> > device provided by them.
> I think the issue here is that he has some sort of unique setup in
> which this name resolution actually DOES provide meaningful information,
> much to the surprise of everyone else on the mailing list.
> Unfortunately, he doesn't realize that this is atypical, so he doesn't
> know enough to report it to us as part of his question.
> Also unfortunately, we don't know what he's actually DOING with this
> name resolution information, so we can't help him.
> Most particularly, we don't know what the various ISP choices are that
> he has, what the gateways of those ISPs are, what the name resolutions
> of those gateways of those ISPs are, or what he wants to do in each of
> the known, possible cases that he may encounter.
> THAT is the kind of information we would need in order to help him.

I can only assume that the OP connects through a number of different
networks which have been set up with, perhaps, different ranges of
IP addresses. For example, and sticking to unroutable addresses, they
might be on 192.168.… in one place, 10.… in another etc.

I have no idea how you'd find out which ISP is being used, except by
making assumptions of this sort, without any connection (assuming
"external" connection). The only sugestion I can give to the OP
would be to use traceroute (if that wasn't blocked too):

$ traceroute -m 4
traceroute to (, 4 hops max, 60 byte packets
 1  router (  0.958 ms  2.627 ms  6.284 ms
 2 (  45.585 ms  45.544 ms  45.594 ms
 3  123.456.789.123 (123.456.789.123)  290.450 ms  290.493 ms  291.698 ms
 4  123.456.798.213 (123.456.798.213)  291.702 ms  291.634 ms  291.832 ms

In my own case, whois on either of the (garbled) addresses above
gives the correct ISP, Cox in Atlanta. Had the question been posed
a week earlier, I could have tried this from various establishments
across four more states.