On 2010-06-25, BARDOU Pierre <bardo...@mipih.fr> wrote:
> I have issues trying to setup this :
>
>    ISP A                ISP B
>      |                    |
>   Router A            Router B
>  Main site  -------  Backup site
>  1.1.1.0/25          1.1.1.128/25

I think you will have to rethink a bit.

Even if your immediate upstreams accept it (which is unlikely without
a special arrangement), there is no way that most of the internet will
accept a /25 announcement. You would want to use at least a /23 for
the whole net, so your site-specific announcements can be /24.

You will also have to ensure connectivity between the two sites
under normal conditions (if you don't have a direct link, then you
could consider a tunnel between addresses from outside this network;
either plain gif/gre and accept the restricted MTU, or you could use a
gre+vether+bridge+pf setup which would let you run at the lowest MTU
of the physical links between them).

> I'd like that connections to the main site flow through ISP A, to the backup
> site flow through ISP B, with backup through the other ISP if one fails.
> So I set up openBGPd like this :
> Router A :
> AS 65001
> network 1.1.1.0/25
> network 1.1.1.128/25 set prepend-self 5

>From one site you would want to announce x.x.x.0/25 and x.x.x.0/24
>From the other you want x.x.x.128/25 and x.x.x.0/24 (or similar with
/24 and /23 if you actually want it to work from the rest of the
internet).

Also: note that 1.0.0.0/8 is an allocated network. Please do not
use addresses from this block even as a test network unless they are
properly allocated to you (which being in europe, they are not).

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