[c-nsp] Classify geographical traffic with BGP

[Walter Keen]

If you are not advertising any space, I would imagine an AS path filter
on ISP-1 (limited to 1 or 2 hops, if that works for you) and no AS path
filter on ISP-2 would do the trick.  You would want a floating static
default route(s) for outbound traffic redundancy.

Now, if you are advertising space, as path prepending may be one way to
go as far as inbound traffic goes, but it gets messy in a situation like
this one.  If you prepend your AS number too many times out ISP1, then
traffic you may have wanted to come in ISP1 may see ISP2 as a closer
route (less AS hops).

Burak Dikici wrote:
>    Hello ,
>
>   I have got one internet router running BGP , and this router has got
> connections with two different ISPs. One of the ISP is local for my country
> and the other ISP's location is outside of my country. I want to classify
> geographical traffic with BGP. For example , local traffic to my country
> will go through ISP-1 (local ISP) , outside traffic to my country will go
> through ISP-2 (outside of my country ISP). What i have to do to achieve that
> kind of configuration ? If i have to use AS path filter , how can i find the
> local ISP AS path numbers and how can i configure AS path filter for this
> request ? Is that enough using the as-path filter just for the national ISP
> or should i use it for international ISP also ?
>
>   If i use AS-path filter for both ISP connections , what will happen to
> redundancy ? I mean , for example i filter national AS numbers at the
> international ISP connection and deny them. Secondly , i filter national AS
> numbers at the national ISP connection , permit them and the other AS
> numbers will be denied. In this situation , what will happen if the local
> ISP connection goes down ? Because of filtering of the national AS numbers
> at the international ISP connection , the BGP table doesn't take any updates
> from the local AS numbers. I hope , i could explain the situation correctly.
>
>
> Kind Regards...
>
> Burak Dikici
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