On Sun, Apr 3, 2016 at 6:17 PM, Mark Tinka <mark.ti...@seacom.mu> wrote:
> > > On 31/Mar/16 10:12, magicb...@hotmail.com wrote: > > > > > > > My questions are: > > > > 1. What could happen in the case of total failure in the redundant > > leased lines? Black hole routing between POPs? > > If you have redundant backhaul that completely fails, you've got real > problems. > > However, if that does happen, any traffic coming into each individual > PoP destined for users in the other PoP will fail. Only traffic > terminating for customers at that PoP will succeed. > > so (as bill points out) plan to localize subnets to each pop. (do not number customers in pop1 in the same /24 as customers in pop2) > > > > > 2. What are the best design methods to avoid this scenario? > > Work on your backhaul. > > Originate specific routes that cover customers present in each PoP, with > the aggregate as a backup route. > > You can run a tunnel across the Internet to simulate a backbone between > both PoP's, using your side of your upstream's IP addresses as the > tunnel end-point. Not elegant, but keeps you up. > > be aware of gre / ip-in-ip forwarding limitations > > > > 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? > > Your fixation on a complete backhaul outage is interesting. > > Purchase backhaul from different service providers to increase your > chances of uptime. > > > different providers, different entrance facilities in the building(s), different conduits out of the area... and hope that somewhere along the path providerA and B didn't share conduit or capacity-swap you to a single path :) > > > > 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? > > See above re: originating more specific routes based on the customers > you have at each PoP. > > > > > > 2.3: other? > > Work harder on your backhaul. > > Yes, bad things can happen, and they do happen. But more than likely, if > a 3-PoP network loses all connectivity from each other, I think routing > will be a much smaller problem to solve in the grand scheme of things. > > Mark. > >
