Re: BCP38.info

[David Miller <dmiller () tiggee com>]

On 1/28/2014 2:16 PM, Jared Mauch wrote:
> On Jan 28, 2014, at 1:50 PM, Valdis.Kletnieks () vt edu wrote:
>
> > On Tue, 28 Jan 2014 08:06:31 -0500, Jared Mauch said:
> >
> > >  52731 ASN7922
> >
> > > It includes IP address where you send a DNS packet to it and another IP address responds to the query, e.g.:
> >
> > > The data only includes those where the “source-ASN” and “dest-asn” of these packets don’t match.
> >
> > Hang on Jared, I'm trying to wrap my head around this.  You're saying that
> > AS7922 has over 50K IP addresses which, if you send a DNS query to that IP,
> > you get an answer back from *an entirely different ASN*? How the heck does
> > *that* happen?
>
> Yup.

Jared,

What you detected is a misconfiguration of devices on those networks,
but that misconfiguration (in and of itself) is not necessarily what is
commonly referred to as "IP spoofing" in the context of BCP38.

You have *not* "shown" that these ASNs "allow IP spoofing".  You have
collected one data point that indicates the mere possibility that these
ASNs allow IP spoofing.

In the example that you provided, you sent a DNS query to a Pacenet
(India) IP and received a response from a Vodafone (India) IP address.
The IP from which you received the invalid response is an open resolver
(bad thing).  It is completely plausible that whatever device is being
queried has interfaces on both networks.

To have "shown" that this ASN "allows IP spoofing" you must have
demonstrated that this response packet, sourced from a Vodafone IP,
entered the "Internet" from a Pacenet router interface.  Unless I am
missing something here, you haven't come close to showing that.

-DMM

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