[c-nsp] Inbound redundancy with two ISPs

[Phil Bedard]

While I'm in favor of the customer ponying up the $ for their own  
ASN, I've seen ISPs that advocate using private ASNs, just to save  
time and money for the customer.   The key that you are missing is  
that the provider that assigns the /24 advertises that along with  
their parent aggregate, so some proper load balancing can occur.    
Otherwise it's just a backup connection.  The "other" ISP may not  
always play ball with this scenario because it appears the space  
originated from them, not the customer, especially larger ISPs.    
Then they have to get an ASN, and might as well get their own prefix  
while they are at it.

Phil


On Nov 1, 2007, at 12:09 PM, Steve Bertrand wrote:

>>>>> 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
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