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Re: more-specifics via IX

  • From: Gaurab Raj Upadhaya
  • Date: Tue Oct 16 06:36:50 2007

Hash: SHA1

Bradley Urberg Carlson wrote:
> I have a few customers' customers, who appear at a local IX.  Due to the
> MLPA-like nature of the IX, I hear their prefixes both at the IX and via
> my own transit customers.  I normally use localpref to prefer customer
> advertisements over peers' advertisements.
> There is a customer's customer who is advertising more-specifics at the
> IX (and using a different source AS, to boot).  I can think of a couple
> ways to prevent hearing these, but thought I should ask for suggestions
> first.

I have seen the opposite of this as well. ISP X announces an aggregate
at the local IX, but has some more specifics announced to the transit
providers for TE needs. To avoid sending/receiving traffic over transit
links and prefer peering route, they were suggested to also announce
their more specific to their peers.

In your case, if your customer's customer is multihomed, they might be
announcing more specific in line with their own routing policies. If you
don't like it - then you'd setup a specific filter, resulting most
probably in asymmetrical routing.

 - gaurab

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