[CentOS-mirror] accuracy of mirrorlist.centos.org

Anssi Johansson

centos at miuku.net
Tue Mar 3 09:35:03 UTC 2015

3.3.2015, 10.33, Seamus Ryan kirjoitti:
> Soooooo what I was wondering is how the initial list is determined?
> Obviously there is some level of geo-smarts involved here as most of the
> mirrors returned at in the same country. But why are a few outside for
> Australia?

Based on your results, I think you are using IPv6. The IPv6 mirrorlist 
behaves differently than the IPv4 mirrorlist. The IPv6 mirrorlist only 
hands out mirrors that are up-to-date and available over IPv6.

Here is the current status of the Australian CentOS mirrors that have an 
IPv6 address in their DNS:

FAIL ftp://centos.mirror.crucial.com.au/
FAIL http://centos.mirror.uber.com.au/
OK ftp://ftp.swin.edu.au/centos/
OK ftp://mirror.overthewire.com.au/centos/
OK ftp://mirror.ventraip.net.au/CentOS/
OK http://centos.mirror.crucial.com.au/
OK http://centos.mirror.digitalpacific.com.au/
OK http://ftp.swin.edu.au/centos/
OK http://mirror.aarnet.edu.au/pub/centos/
OK http://mirror.colocity.com/centos/
OK http://mirror.overthewire.com.au/pub/centos/
OK http://mirror.ventraip.net.au/CentOS/
OLD ftp://mirror.aarnet.edu.au/pub/centos/

The first two are not reachable over IPv6, even though they have an IPv6 
address in the DNS. The last one at AARNet is stuck in 17th February, 
and the three ftp mirrors are also available over http. This leaves us 
with seven usable IPv6-capable mirrors in Australia.

The IPv6 mirrorlist always outputs a list of 10 mirrors. If there aren't 
10 mirrors in the specified country, it will pick mirrors from a 
predefined list of global fallback mirrors. Yes, those include mirrors 
in USA, Canada, Japan and Ireland. The fastestmirror plugin will usually 
weed out those global fallback mirrors so they don't actually get used.

There are 41 IPv6-capable CentOS mirrors in US, so the global fallback 
mirrors don't get used there as often as in other countries.

Once more mirrors enable IPv6, the need to include those global fallback 
mirrors in the list is reduced.

While I'm at this, a few remarks to mirror admins: If you enable IPv6 on 
your mirror, you do not need to announce it on this list. The mirror 
checker will pick those up automatically once your DNS has updated. If 
you enable IPv6 on your mirror, please check that IPv6 works on all 
protocols you support (http, ftp, rsync). You can check your mirror's 
IPv6 status from http://miuku.net/ipv6reach/

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