Connecting to 2 Different ISPs

Unanswered Question
Apr 12th, 2010

Quick question...

This is the scenario.

large enterprise

2 Internet routers, each running eBGP with a different ISP than the other. iBGP between them.

How does the enterprise obtain a public IP address space that would be advertised by both ISPs?

usually you buy an IP address block from an ISP, right? So, what Im thinking is that there must be a way to buy an IP address block independent of the ISPs ...

I know this is a very basic question, but I never had to concern myself with the mechanics of this....


I have this problem too.
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huangedmc Mon, 04/12/2010 - 21:27

You'll need to justify your need for your own IP space w/ ARIN.

If you have solid justification, they'll assign you a block.

Faisal Shahid Mon, 04/12/2010 - 23:56

In your scenario, as you are connected with two different ISPs, relevent registrar can assign your organization a /24 address space. you will have to apply for Multihoming assignment, I think they charge membership fee and address space fees as well. They will ask you about the details of your setup, like network diagrams and the justification that why you need your own address space.

Organization in multihoming setup, usually get their own address space to create fault tolerent networks, as ofcourse if one ISP gets down an address space from that ISP cannot be routed through the network of other ISP, and if you have your own address assignments advertised by BGP through both ISPs, your network remains accessable if one ISP gets down through another ISP.

below are the links for the registrar responsible for the allocation in their respective regions.

For Africa region,

For Asia Pacific,

For North America,

For Latin America,

For Europe, Middleeast and Central Asia,

Hope to help


Faisal Shahid


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