Re: How Not to Multihome

[Andy Davidson <andy () nosignal org>]

On 8 Oct 2007, at 22:43, Keegan.Holley () sungard com 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?

There was a good discussion following this, but I couldn't find  
mention of IRR Consistency in the follow ups.

If I publish in an IRR that I am the legitimate originator of a  
prefix, 10.0.0.0/19, and someone else announces 10.0.2.0/24, whether  
I am aware or not, then they get the traffic. This could be the  
desired outcome, as in the scenario the OP refers to.

However, if a different third-party network then sweeps up their  
routing table by looking to remove more specifics that seem 'spoofed'  
using IRR data, the routes you intend to push onto the internet may  
well start to disappear from their perspective.

I'm talking in fairly superficial terms, rfc 2650 might give you more  
ideas.  There's a reason things 'tend' to be done one way even though  
it means burning through AS numbers and v4 address resources.