[c-nsp] Inbound redundancy with two ISPs

[Steve Bertrand]

>>>> Is multihoming a valid reason even if they can't justify a /24 worth 
>>>> of IP addresses?  I would have thought that ASNs were hard to get 
>>>> since there's a finite number of them (currently anyways).
> 
> Please don't spread FUD.  Multihoming has been and continues to be valid 
> justification for ONE of the ISPs to assign a /24.  See 
> http://www.arin.net/policy/nrpm.html#four236 for the policy.  Same with 
> ASNs - if you have a justifiable need, you get one.

It doesn't seem to me that he was trying to spread FUD. It appears as a
legitimate question doesn't it?

> BGP is the method.  If for some reason someone or something says "BGP is 
> not an option", that someone or something needs to be eliminated from 
> the puzzle.  I've done BGP with a fractional T1 customer, they can do it 
> too.

So, if I understand you right, this is what you would propose, assuming
that you were provider 'A', and it was your /24 you were assigning to
the OP:

- 'A' routes a /24 to OP
- OP advertises the /24 to provider A and B via BGP with personal local
preferences in place
- A advertises it's aggregate including the /24 to the 'net
- B advertises the more specific /24 prefix to the 'net
- OP uses an ASN from the private range, which both A & B must agree to
honour

I'd really like to understand this, because I've never had to deal with
a situation where I've received a prefix from one ISP and needed to
multi-home with it. (I have my own ARIN prefix).

Will the more specific /24 route advertised to the 'net by B not be the
preferred route at all times?

Steve