BGP Homing Question

Sat Aug 28 19:10:57 UTC 2004

On Aug 28, 2004, at 12:02 AM, Michel Py wrote:

>> It is your netblock, you get to use it as needed.
>
> This is not a good reason; it might be a good excuse, but not a good
> reason.

Really?  So if I have a /20, you are saying I cannot use it as I need 
to use it?

>> Also, filtering will not be an issue, if you are careful.
>> Anyone who does not hear the /24 will hear the /20.
>
> Rick, you do need to tunnel the EU block from your US location back to
> your EU location, for people that are behind a filter that masks your
> /24. It does not happen often but it does happen. This leads to
> suboptimal asymmetric traffic, double whammy in terms of bandwidth
> (EU-bound traffic received by the US site from people that see the /20
> and not the /24 that has to be re-sent back to EU over the tunnel) and
> interesting issues with stateful firewalls though.

You do not need to tunnel at all if your two upstreams trade downstream 
routes (e.g. "peer"), and the US upstream does not filter small 
prefixes from their peers.

As I said in the first post, this is much more common than the 
alternative, so chances are it will "just work".

-- 
TTFN,
patrick