2 upstreams 1 downstream BGP configuration optimization

[Toke Høiland-Jørgensen]

Kevin B <test at teslahost.net> writes:

> Hello,
>
> 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?

Because you are telling Bird (with that filter) to export any net in
that prefix? I.e.,

if net ~ [ 10.40.40.0/24 ] then return true;

doesn't care where that route is coming from.

If you want to control where announcements come from, you can do that in
the filter. E.g.,

if proto != "DOWNSTREAM1v4" then return false;


-Toke