This is probably your best resource:
http://www.netaxs.com/~freedman/bgp/bgp.html
----- Original Message -----
From: "andyh"
To:
Sent: Wednesday, May 09, 2001 5:47 PM
Subject: Re: Changing ISPs [7:3831]
> 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]
> 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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