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How do you ensure that two data network links have no SPOF (Single Point of Failure)?

We are working on a datacenter network connectivity and need to ensure that there will be no SPOF. We will have two network links to connect to the data center.

The question is: how do you make sure that the two links have no SPOF?

Would you recommend to order the two links from the same network provider? or different providers? And if different providers, what level of information do you typically get?

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up vote 4 down vote accepted

This can be an expensive proposition. In the past we had two separate providers. We had to stipulate they had to come from different Central Offices (CO) and arrive at the building from different paths. This can be very expensive. Usually the carriers will both want to come from the closest CO and probably follow the same conduit and entry point into the building.

You will need to get very specific with them, and get the engineering details. You will probably need to pay one of them much more for the longer distance from the further away CO. Also one of them will probably need to create a new path into your building so that one backhoe operator can not take out both networks.

We had to specify even that the entrance to our business park had to be from opposite ends so that they two carriers did not share any conduit.

Once again, all of this can get expensive quickly, but is necessary for you to get what you are asking for.

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It all depends on physical connectivity. The only way to achieve real redunancy is to get different providers with different physical connectivity (that they don't share the same fibre over MPLS or similar). I've seen many cases where businesses thought they had redunant internet with BGP etc, only to find out that Joe Average and his Catepillar digger could easly render them to a halt.

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@Erik Yes, I agree. But what level of information do you request from your providers and do you send [provider #1]'s information to [provider #2] so that [provider #2] can confirm they do not share any physical connectivity? or do you analyze all information yourself? – Steven Feb 16 '10 at 11:27
That's the tricky part. In my location there is a plethora of ISP's avaible, wich all clams to have redunant MPLS-ring networks - but they usually lease the lines from the same backbone provider. It's not easy to find this out, because you have to dig and ask who they rent the lines from. I'm not sure how you should go at this, but perhaps asking your different providers for a price offer with emphasis on no shared physical media? Maybe you also should look at having one main "pipe" over fibre and a backup link over SDSL or similar? – pauska Feb 16 '10 at 12:05

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