looking for hostname router identifier validation

Tue Apr 30 12:12:05 UTC 2019

While at NTT and at Akamai we have managed to publish sane PTR records and make the forward work as well. You need to automate it by pulling from your router configuration database and publish to your DNS database. If you are still doing either by hand then it’s time to make the switch ASAP. 

Sent from my iCar

> On Apr 29, 2019, at 4:13 PM, Eric Kuhnke <eric.kuhnke at gmail.com> wrote:
> 
> I would caution against putting much faith in the validity of geolocation or site ID by reverse DNS PTR records. There are a vast number of unmaintained, ancient, stale, erroneous or wildly wrong PTR records out there. I can name at least a half dozen ISPs that have absorbed other ASes, some of those which also acquired other ASes earlier in their history, forming a turducken of obsolete PTR records that has things with ISP domain names last in use in the year 2002.
> 
> 
> 
>> On Mon, Apr 29, 2019 at 6:15 AM Matthew Luckie <mjl at luckie.org.nz> wrote:
>> Hi NANOG,
>> 
>> To support Internet topology analysis efforts, I have been working on
>> an algorithm to automatically detect router names inside hostnames
>> (PTR records) for router interfaces, and build regular expressions
>> (regexes) to extract them.  By "router name" inside the hostname, I
>> mean a substring, or set of non-contiguous substrings, that is common
>> among interfaces on a router.  For example, suppose we had the
>> following three routers in the savvis.net domain suffix, each with two
>> interfaces:
>> 
>> das1-v3005.nj2.savvis.net
>> das1-v3006.nj2.savvis.net
>> 
>> das1-v3005.oc2.savvis.net
>> das1-v3007.oc2.savvis.net
>> 
>> das2-v3009.nj2.savvis.net
>> das2-v3012.nj2.savvis.net
>> 
>> We might infer the router names are das1|nj2, das1|oc2, and das2|nj2,
>> respectively, and captured by the regex:
>> ^([a-z]+\d+)-[^\.]+\.([a-z]+\d+)\.savvis\.net$
>> 
>> After much refinement based on smaller sets of ground truth, I'm
>> asking for broader feedback from operators.  I've placed a webpage at
>> https://www.caida.org/~mjl/rnc/ that shows the inferences my algorithm
>> made for 2523 domains.  If you operate one of the domains in that
>> list, I would appreciate it if you could comment (private is probably
>> better but public is fine with me) on whether the regex my algorithm
>> inferred represents your naming intent.  In the first instance, I am
>> most interested in feedback for the suffix / date combinations for
>> suffixes that are colored green, i.e. appear to be reasonable.
>> 
>> Each suffix / date combination links to a page that contains the
>> naming convention and corresponding inferences.  The colored part of
>> each hostname is the inferred router name.  The green hostnames appear
>> to be correct, at least as far as the algorithm determined.  Some
>> suffixes have errors due to either stale hostnames or incorrect
>> training data, and those hostnames are colored red or orange.
>> 
>> If anyone is interested in sets of hostnames the algorithm may have
>> inferred as 'stale' for their network, because for some operators it
>> was an oversight and they were grateful to learn about it, I can
>> provide that information.
>> 
>> Thanks,
>> 
>> Matthew
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