[CentOS-mirror] IRC meeting regarding new mirroring system for CentOS

Peter Pöml peter at poeml.de
Wed Nov 10 09:54:37 EST 2010

Hi Randy,

On Tue, Nov 09, 2010 at 08:22:10 -0500, Randy McAnally wrote:
> > Regarding this, I would like to question the need for such manual 
> > configuration. centos.eecs.wsu.edu is your mirror, right? Without 
> > any configuration, MirrorBrain would send you all requests from 
> > clients out of (if there isn't any mirror in the same 
> > network of course). If a client is not in that particular network, 
> > but within AS10430, it would still get sent to your mirror -- if 
> > there is no other mirror in that autonomous system. Would there be a 
> > second mirror in your autonomous system? That's the question. If not,
> >  everything would happen automatically anyway. No need to juggle 
> > lists of network prefixes. (And no need to make such configuration 
> > accessible, which could result in a security issue after all, if not 
> > handled carefully.)
> > 
> > So far, I didn't encounter a case where clients are outside the 
> > network prefix of a mirror, but within the same AS, and there is a 
> > second mirror in that AS -- so there was no need to add a way to 
> > specify network prefixes at all.
> We have two mirrors in our AS, which has several IP ranges split across two
> datacenters over 2000 miles apart.  Being able to specify a CIDR for each
> mirror would be nice since there's no guarantee an AS lookup alone is going to
> get it right.. but I suppose as long as BOTH mirrors are returned on a mirror
> list, the fastest mirror plug in could easily choose the correct mirror.

Might be that your case would be handled just automatically. Are & your two mirrors? (That's what
mirror.fast-serv.com resolves to.)

Okay, let's see :-)

The two mirrors are in AS29889, for which the following prefixes are

 select * from pfx2asn where asn = 29889;
       pfx       |  asn  
-----------------+------- | 29889 | 29889 | 29889 | 29889  | 29889

This is what GeoIP currently has to say about these network:

 1) AS TW Taipei
 2) NA US Maryland Crownsville 39.030102,-76.606903
 3) NA US Maryland Crownsville 39.030102,-76.606903
 4) NA US California Escondido 33.134899,-117.041603
 5)  NA US Virginia Herndon 38.984100,-77.382698

So we have:

1) I'm not sure if that is a GeoIP glitch regarding,
claiming that it is in Taipei? Might that be wrong? Anyway, clients from
that range will be sent to one of your two mirrors, because they are in
the same AS (unless another mirror in the same IP range exists). 

2) clients will be sent to your mirror in Maryland. None
of your mirrors is in the same IP range, both are in the same AS, and
the Maryland mirror is preferred because it is geographically closer.
Which should be what you want, right?

3) clients will be sent to your mirror in Maryland,
because it is in the same IP range.

4) clients will be sent to your mirror in California,
because it is in the same IP range.

5) clients are sent to your mirror in Maryland. None of
the two mirrors is in that IP range, but both are in the same AS, and
the Maryland is geographically much closer, while the other one is over
2000 miles away. MirrorBrain picks the one in Maryland therefore.

Is that the situation, or did I guess it incorrectly? Are there further
networks that need consideration? Are the results which I described
above how you want it to be?

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