Support for dual AS and AS migration

[Ondrej Zajicek]

On Mon, Mar 05, 2018 at 07:22:22AM +0100, Tore Anderson wrote:
> * Lennert Buytenhek <buytenh at wantstofly.org>
> 
> > Somewhat related to this, I wrote this patchset last year:
> > 
> > 	http://trubka.network.cz/pipermail/bird-users/2017-March/thread.html#11084
> > 
> > The idea was to let you configure two AS numbers that a remote peer
> > can connect to us with, so that the remote peer can be reconfigured
> > to use a different AS number without the local machine needing to
> > reconfigured at the same time.
> > 
> > If there's interest in this patchset I can dust it off and try
> > resubmitting it.
> 
> Hi Lennert,
> 
> In case you do decide to work on this again, I'd suggest you take a
> look at the FRR / Cumulus feature where you can configure a
> peer/peer-groups ASN to be the string «external». This means to accept
> the peer to be in any arbitrary ASN (except for the local one).
> 
> I've found this to be a very convenient feature, and it'd be nice to
> see it in BIRD too.

Hi

The original patchset allowed accepting both internal and external BGP
sessions on one BGP instance, which makes it more complicated that just
accepting multiple AS numbers. Esp. with BIRD 2.0.1, which supports also
BGP confederations and therefore has three discinct kinds of BGP
sessions.

I think that reasonable interface would be to allow to specify the number
set (of allowed AS numbers), like is used in filters, but still keep it
limited to one kind (internal, external, inter-confederation) of BGP sessions.

Such feature we would accept or perhaps i will implement it someday.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."