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Let's assume I'm running web service and estimate two possible solution.

Basically I'm looking for answer from business point of view.

But I would like to see from any other point of view anyway.

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up vote 5 down vote accepted

If you don't need to be connected to other ISPs directly, in other words - if you trust your ISP to function up to your SLA commitments for this web service, you can just grab IP block from him and live with that. IP block will propably come from ISP PA block (Provider Aggregatable).

However, if you want to be connected to multiple ISPs, run multihoming and have added redundancy to the solution, you need to have AS to request PI block (Provider Independent). It's usual practice to follow this way, as pros of having connection to two different ISPs usually win the con of having additional connection & paying for it.

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Not to forget that you can change your provider more easily when using PI. And that you'll have no chance of getting IPv4 PI in some / most parts of the world. – Jens Link Aug 18 '14 at 8:44
@JensLink It makes sense! More info:… – Paul Chechetin Aug 18 '14 at 9:09
@Paul: I know. I just thought it's worth mentioning in this discussion. Just had a discussion with a customer last week about this topic. – Jens Link Aug 18 '14 at 9:15

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