2 upstreams 1 downstream BGP configuration optimization

[Job Snijders]

Dear Kevin,

On Tue, Jun 04, 2019 at 03:00:53PM +0000, Kevin B wrote:
> I have 2 upstream transit providers and 1 downstream customer we provide
> transit to - http://paste.debian.net/1086030/ (full Bird configuration with
> explanation)
> 
> There is a problem: Bird is exporting all the imported prefixes from
> my upstreams back to them. For example 10.40.40.0/24 is being exported
> from us even when AS20's customer doesn't announce it, because it is
> announced somewhere else in the full table and we just export it back
> from the full view.
> 
> Here is `birdc show protocols all` output - http://paste.debian.net/1086033/
> 
> I would like to prevent exporting the full view tables imported from
> my upstreams back to them, can you help me to understand what is wrong
> with the configuration and why does it happen?

You'll have to mark the routes you receive on 'import', and act on those
markers on 'export'.

I've spoken a bit about how to make robust routing policies, I hope this
is of use to you:

    https://ripe77.ripe.net/archive/video/Job_Snijders-B._BGP_Policy_Update-20181017-140440.mp4

    https://ripe77.ripe.net/presentations/59-RIPE77_Snijders_Routing_Policy_Architecture.pdf

Specifically in your example, I've added the use of BGP Large
Communities to help arrange what announcements go where, please compare
this untested example with your own deployment: http://paste.debian.net/1086041/

Kind regards,

Job