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, "magicb...@hotmail.com" <magicb...@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.
>
