Re: Ownership of Routers on Both Ends of Transnational Links

[Christopher Morrow <morrowc.lists () gmail com>]

On Tue, Apr 16, 2019 at 5:19 PM Nimrod Levy <nimrod () nimrod is-a-geek net> wrote:
> On Tue, Apr 16, 2019, 16:52 Ross Tajvar <ross () tajvar io> wrote:
> > I think it's clear that the IPs belong to Telia, but I understood James's point to be that the router using the IP 
> > in question may belong to China Unicom. (I agree with that, I was not thinking clearly this morning.) As this is an 
> > interconnect link, one side must belong to Telia and the other to China Unicom. The question, then, is which side 
> > are we looking at? Well, first I want to know how big the subnet is. I assume either /30 or /31. So, I do a reverse 
> > DNS lookup on all the IPs in the surrounding /30 block:
> > 62.115.170.56 - sjo-b21-link.telia.net
> > 62.115.170.57 - chinaunicom-ic-341501-sjo-b21.c.telia.net
> > 62.115.170.58 - las-b24-link.telia.net
> > 62.115.170.59 - chinaunicom-ic-341499-las-b24.c.telia.net
> > That looks like two /31s. Only one IP in each has the name of China Unicom in it, so that one is probably in use by 
> > China Unicom, and the other is probably in use by Telia.

that was my point yes.

> I think we're making a lot of assumptions about how well PTR records are maintained. All of this could be totally 
> accurate. Or...not...

this is totally true :) but... if the next hop after
chinaunicom-ic-341501-sjo-b21.c.telia.net is a CU ip... it's better
than average chance that the
chinaunicom-ic-341501-sjo-b21.c.telia.net

address is a telia /30 (or /31) on the ptp link between CU/Telia. That
Telia owns the ip space and that PROBABLY the customer identification
is correct. (cu)

-chris