[AusNOG] AARNET and Aggregates

[Sean K. Finn]

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: ausnog-bounces at lists.ausnog.net [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Jonathan Thorpe
Sent: Wednesday, 11 November 2009 10:12 AM
To: AusNOG at ausnog.net
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 (http://lg.aarnet.edu.au/cgi-bin/lg), 
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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