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<small><font face="Verdana">Hi All,<br>
<br>
Thanks for the replies.<br>
<br>
AARNET are favouring a less specific path (i.e. preferring the /20 over
the /24). Not only that, the AS paths for the /20s are also longer than
those that they see for the /24, so it doesn't make a lot of sense.<br>
<br>
The aggregation is internal - we have a large number of /28-27s that we
aggregate as /24s and export those routes (and only /24s) to the
peering networks (e.g. Equinix). The transit providers (e.g. AS703)
receive the full advertisement of /20s only (no /24s).<br>
<br>
I tried advertising the /20s in addition to the /24s to Equinix to no
avail.<br>
<br>
The only clue I have at the moment is that this affects other networks
that peer with Equinix that also have routes that have been aggregated
at some point (in other words, they show up as "aggregated by
<AS>").<br>
<br>
Has anyone else observed this behaviour?<br>
<br>
Kind Regards,<br>
Jonathan<br>
</font></small><br>
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<br>
Sean K. Finn wrote:
<blockquote
cite="mid:D2B93227AFAE51499A4F7E1BEDD4523A3AC8EB10A9@msx01.office.ozservers.net.au"
type="cite">
<pre wrap="">Do you mean that if you advertise a /20 and a /24 that the route that is preferenced is the /24 ?
I.e. the more-specific route (/24) takes precedence over the aggregated route (/20) ?
-Sean.
-----Original Message-----
From: <a class="moz-txt-link-abbreviated" href="mailto:ausnog-bounces@lists.ausnog.net">ausnog-bounces@lists.ausnog.net</a> [<a class="moz-txt-link-freetext" href="mailto:ausnog-bounces@lists.ausnog.net">mailto:ausnog-bounces@lists.ausnog.net</a>] On Behalf Of Jonathan Thorpe
Sent: Wednesday, 11 November 2009 10:12 AM
To: <a class="moz-txt-link-abbreviated" href="mailto:AusNOG@ausnog.net">AusNOG@ausnog.net</a>
Subject: [AusNOG] AARNET and Aggregates
Hi All,
I've been trying to track down an odd problem that I've noticed over the
past few days and hope someone can shed some light on this.
Looking at AARNet's looking glass (<a class="moz-txt-link-freetext" href="http://lg.aarnet.edu.au/cgi-bin/lg">http://lg.aarnet.edu.au/cgi-bin/lg</a>),
it seems that routes that are flagged as aggregated are ignored when
there are routes available that are not aggregated, despite having
longer AS paths.
This results in inbound traffic that we would prefer to come in over
peering networks (e.g. Equinix) entering our network over transit
instead. This is not ideal because it results in using more expensive
bandwidth and is a bit more asymmetrical than we'd like.
At first, I thought it was just us (we advertise two /20s as a series of
/24s - e.g. 122.202.64.0/24 and 203.124.176.0/24 under AS37996 which are
aggregates of smaller prefixes), but looking at other peers that show up
over our Equinix link, others that also have aggregated routes seem to
experience the same phenomenon.
I've written to the AARNET NOC already, however I'm wondering if this
could be by design or simply a side effect?
Thoughts anyone?
Kind Regards,
Jonathan
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</pre>
</blockquote>
<br>
<br>
<div class="moz-signature">-- <br>
<meta content="text/html;charset=windows-1252" http-equiv="Content-Type">
<title>Re: error message</title>
<small><font face="Verdana">Jonathan Thorpe<br>
Conexim Australia<br>
<a class="moz-txt-link-abbreviated" href="http://www.conexim.com.au">www.conexim.com.au</a><br>
Phone: 1300 133 900<br>
Direct: +61 2 8214 5804</font><br>
</small><br>
<br>
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