North American Network Operators Group
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Re: BGP Homing Question

  • From: Patrick W Gilmore
  • Date: Sat Aug 28 15:13:09 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