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Ownership of Routers on Both Ends of Transnational Links

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: - sjo-b21-link.telia.net - chinaunicom-ic-341501-sjo-b21.c.telia.net - las-b24-link.telia.net - 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.

On Tue, Apr 16, 2019, 3:50 PM Christopher Morrow <morrowc.lists at gmail.com>

> On Tue, Apr 16, 2019 at 10:59 AM James Jun <james.jun at towardex.com> wrote:
> > More likely, thease routers are China Unicom's routers in their US POP,
> not managed by VZ/Telia.
> > The /30s in this case are unmanaged IP transit hand-offs, coming in as
> Nx10G or 100G.  When your
> > IP transit provider assigns the /30, your router looks like it belongs
> to your upstream, common
> > mistake when interpreting traceroutes[1].
> >
> $ nslookup
> name = sjo-b21-link.telia.net.
> if you model (as james says) each interconnect as a /30 or /31 ...
> look for the adjacent ip and see the PTR for that ip.
> (the above is your first link example's peer ip)
> > [1]: see Page 22 on
> https://www.nanog.org/meetings/nanog47/presentations/Sunday/RAS_Traceroute_N47_Sun.pdf
> >
> > James
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