North American Network Operators Group

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Re: How Not to Multihome

  • From: Joe Provo
  • Date: Mon Oct 08 18:29:10 2007

On Mon, Oct 08, 2007 at 05:43:03PM -0400, [email protected] wrote:
> I have a client that wants us to advertise an IP block assigned by another 
> ISP.  I know that the best practice is to have them request an AS number 
> from ARIN and peer with us, etc.  However, I cannot find any information 
> that states as law.  Does anyone know of a document or RFC that states 
> this?

If the address space is assigned to another provider, getting 
clarification from them directly or indirectly(*) that the customer 
is allowed to use it, if it is portable or allowed to be seen
outside their ASN, etc. If their are truly attempting to multihome,
doing so with multiple-origin ASNs can create nondeterministic
behavior in the exact failure conditions that multihoming is
seeking to solve.  Given the clue level of the customer or their
business/traffic, it may not matter (anycasters, CDNs, or other 
edges with levels of indirection).  

Most ISPs quite simply have a policy that multihoming is done by 
BGP in such and such fasion and that's that.



(*) whois delegation at best, some providers indicate portability 
   or multihoming policy in whois or IRR allocations,etc

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