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Re: Assigning IPv6 /48's to CPE's?

  • From: Rick Astley
  • Date: Thu Jan 03 05:56:23 2008
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On Jan 3, 2008 4:10 AM, Mikael Abrahamsson <[email protected]> wrote:
On Thu, 3 Jan 2008, Rick Astley wrote:

> If Bob has a multihomed network, he can't just give one /48 to a customer in
> NY and the next one to a customer in CA unless he wants to fill up Internet
> routing tables with /48's, so he will have to assign large aggregate blocks
> to each region.

Could you please elaborate on this? Unless Bob is actually breaking the
"single AS needs to have common IGP and be connected internally", I don't
understand the relevance of your statement above. Just because he's
multihomed doesn't mean he can't just announce /32 and then internally
handle the routing (of course he should do aggregation though, but perhaps
is smaller chunks).
 
Because announcing more specifics is more granular. Lets say we are both nationally connected and I peer with you in only one location (say CA).

If we both announce only one aggregate block to each other, if I am trying to get to you in NY from NY, we are going to do it through California (not good).

The same scenario happens if we peer on both sides of the country and one of the sessions goes down.

In this case the best path is probably me > someone else > you.

Now instead what I can do is tag my california routes with a "california" bgp community, and export only those specific routes to you there.
This way your traffic to me in NY will not go over this session.

Now unless you want a pile of /48's handed to you over this session, it is good practice for me to aggregate my routes based on location as best I can.