The relevant portion of Tony's explanation (which is very concise) is the
following --++> but should see the route via P2 if P1 is accepting it. (Some
++> may either block the announcement or have anti-spoofing packet filters
++> at their borders that block the traffic itself).His explanation is very good but the statement that Seth made was that many
providers DO block the /24 announcements. Tony doesn't say anything
specifically about this.
So the example is that you're numbered out of Provider1's CIDR block.
You're fearing that Provider1 will block announcements of more-specifics
from w/in their own blocks. My anecdotal understanding (which I agree has
limited value) was that providers who filtered made *exceptions* in their
filtering policies for their own CIDR blocks.
*** What policies any other providers have is unimportant to my example
and things will work just fine no matter the case with those people. ***
At any rate, since you're a paying customer of P1, you at least have
some influence to exert to get them to make exceptions.
As for packet filters (vs. route filters), I doubt many ISPs would
implement such a thing as that filtering is typically done at the
customer edge.
Tony