depends if you use PI or PA space:
PI - Provider Independant space, this if effectively "owned" by your AS -
believe it used to be called "mobile", although there are still restraints
regarding global routability if you wish to move it between continents -
some Tier-1 ISP will filter on intercontinental links based on the
route-registry origin (ARIN, RIPE, APNIC, etc.
PA - Provider Allocated (or Assigned I can never remember which way around
the route-registries label these things). This is allocated/assigned to you
from your provider, from one of their own aggregate block, and you cannot
"take it with you" if you leave that ISP.
Generally PI space is preferred, there should be no problem routing this
through any provider, and you can move with impunity (subject to
restrictions on moves of an inter-continental nature, as per above). All
you need to ensure this that your routing policy, and that of your upstream,
with the appropriate registry is correct.
PA space is more tricky, and is at the discretion of your "secondary"
provider(s). Some do, some don't - try your luck ;-) It is "legal" to
route a more-specific prefix of a provider's aggregate block - I had a chat
to RIPE about this a while back, and although not documented, they are keen
to lessen the amount of PI space they give out. The difference here is that
although you are advertising a route that is included in your provider's
aggregate prefix, you are advertising a different prefix, and as BGP works
on a per-prefix basis it doesn't discriminate between the overlapping
routes.
hope that makes sense
Andy
----- Original Message -----
From: "Brett Johnson"
To:
Sent: Wednesday, May 09, 2001 4:37 PM
Subject: Changing ISPs [7:3831]
> If I acquire an AS number and use it with two providers what happens if in
a
> year or two
> I decided to change one of the providers. Do I have to inform ARIN or
> acquire a new AS
> number? What would be the process of informing the Internet (through BGP)
> when changing
> the ISP? How about if I added a third ISP instead of changing ISPs?
>
> Thank you
>
> Brett Johnson
> FAQ, list archives, and subscription info:
http://www.groupstudy.com/list/cisco.html
> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
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