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.
