Re: Some doubts on large scale BGP/AS design and black hole routing risk

["Bill Woodcock" <woody () pch net>]

Are respondents to suppose that the customer base and address space are evenly divided between the two cities, and that 
the ISP is too clueless to originate each /23 from the city that uses it, in iBGP?

    
                -Bill


> On Apr 3, 2016, at 15:04, "magicboiz () hotmail com" <magicboiz () hotmail com> wrote:
>
> Hi everybody!
>
>
> as part of laboratory work at the university,  I'm working on a BGP design study, and I would like to post some 
> questions regarding IP address space allocation and its impact on BGP which are breaking my mind :)
>
> Let's suppose we have an ISP/AS with two POPs: PARIS and LONDON. These two POPs are connected with redundant leased 
> lines. Each POP has a BGP router speaking eBGP to different ISP providers/upstreams and also, each POP run its own 
> OSPF area/ISIS area. Something like this:
>
>
> <INET> ---eBGP---<LONDON POP-ospf area1>===redundant leased lines (ospf area0)===<PARIS POP- ospf 
> area2>---eBGP---<INET>
>
> Now, this AS/ISP gets one /22 prefix from it RIR (RIPE in this case), and starts to announce it to its upstreams in 
> PARIS and LONDON at the same time.
>
>
> My questions are:
>
> 1. What could happen in the case of total failure in the redundant leased lines? Black hole routing between POPs?
>
> 2. What are the best design methods to avoid this scenario?
>
>   2.1: adding a third POP creating a triangle? What if a POP looses connection with the other two POPs at the same 
> time? Another black hole?
>
>   2.2: requesting another prefix and allocating 1:1 prefix:POP, so in the scenario each POP only would announce its 
> prefix to the upstreams?
>
>   2.3: other?
>
>
>
> Thanks in advance!
> J.