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Re: How Not to Multihome
On Oct 8, 2007, at 9:46 PM, Justin M. Streiner wrote:
On Mon, 8 Oct 2007, Patrick W. Gilmore wrote:
Well, "internally" is kinda useless to this discussion, wouldn't you think?
I get the feeling that you are trying to ask a clever question there, but it didn't come across that way.
Off the top of my head, I don't see why the provider who holds the parent block would do this externally. If the provider has, say, a /18 and they assign a /24 of that to this customer, there would be no legitimate reason to originate that /24 and propagate it out to the rest of the Internet. Note that I don't consider breaking that /18 up into 64 /24s and announcing them all separately to accomplish some sort of poor-man's traffic engineering to be a legitimate reason :)
Interesting. Did you not read the first paragraph in this e-mail? In fact, I seem to recall that you wrote it (attribution is missing, so I can't be 100% certain).
Personally, I'd call that a "legitimate reason".
To be clear, I am not suggesting de-aggregating every CIDR down to / 24s. But the global table doesn't grow any more whether the customer announces the /24 from their own ASN, or if you muti-originate it from two upstreams - or just one upstream for that matter. So there is no "legitimate reason" to _not_ announce it, but there is a reason to announce it.
-- TTFN, patrick