Adding a downstream ebgp connection. How to keep it separate?

[LU]

Hi.

So, the Linux BGP routers perform packet forwarding. Up until this point
they were handling only my own network/prefixes/traffic. Everything is
using the default linux/bird main tables.

I want to provide connectivity to the customer. I would announce his prefix
to a select few of my upstream eBGP sessions and also export some of the
upstream routes to him.

So, at the very least I need a separate routing table (on linux) to have a
different FIB for my own traffic and the customer's.

But since I want to export some routes to the customer (and not just a
default route) I need a way to be able to hand off him the raw upstream
routes that I receive via eBGP. When I receive upstream routes I process
them with filters (some get rejected, some I set a different local
preference, etc. in the end they are modified to suit my use cases).

So this is what I am asking: does it make sense to have a separate bird
table per each upstream eBGP session so that I can keep the raw routes
there, and eventually feed them via the pipe protocol to my own routing
table for processing, and to the customer's table?

Hope this makes sense.

Thanks.







wt., 19 mar 2024 o 23:34 Alexander Zubkov <green at qrator.net> napisał(a):

> Hi,
>
> I think you need to start with explaining why do you want to keep
> customer and upstream routes in separate tables.
>
> Regards,
> Alexander
>
> On Tue, Mar 19, 2024 at 1:39 PM LU <zyash911 at gmail.com> wrote:
> >
> > Hello.
> >
> > I have two BGP routers with bird 2.4. Each router maintains some eBGP
> connections to upstreams where I announce my prefixes. These routers have
> an iBGP connection between themselves to exchange routes learned from those
> eBGP connections.
> >
> > I do some filtering on the eBGP connections (like setting local
> preference, as path prepending, setting an internal bgp community so that I
> know which routes originate from which eBGP connection, etc.)
> >
> > So far this is simple, works great for my own traffic/prefixes and have
> no trouble maintaining this.
> >
> > But now a need arose that I will be adding a downstream eBGP connection
> (customer). This means transiting a foreign prefix over my BGP routers and
> exporting some routes to it.
> >
> > How do I approach this the cleanest and simplest way possible?
> >
> > I suppose I should have two routing tables (currently under Linux/Bird
> everything is under the default routing/main table):
> >
> > - main table (keep for my own traffic)
> > - customer table
> >
> > But I am unsure what to do with my existing upstream eBGP connections
> since I do some filtering on them for my own use cases.
> >
> > Should I have a separate Bird table for each upstream eBGP connection?
> Then use the pipe protocol to put the routes in the main and customer table
> separately?
> >
> > Then I could place the current filtering of eBGP connections that I use
> for myself in the pipe protocol that feeds my main table?
> >
> > The customer table will then be piped the raw routes from the eBGP
> connections.
> >
> > Is my thinking correct? Or this can be done better/differently?
> >
> > Are there perhaps any presentations and/or sample configs of such
> setups? I am sure this situation comes up quite often.
> >
> > Thanks!
> >
> >
> >
> >
>
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