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

Mon Apr 4 03:28:50 UTC 2016

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 at hotmail.com" <magicboiz at 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.
> 