BGP Routing Question

At our corporate office we currently have a 60Mb connection to the internet through Time Warner.  For redundancy we are adding an additional 50MB connection through AT&T.

We have another location that is co-located in our parent companies datacenter. They already have multiple providers and currently use BGP.

If I get a /24 block of IPs from ARIN is it possible for me to split that block up and BGP advertise a portion through Time Warner here at my corporate office and get a provider at my parent company to advertise the other portion.

What I want to get to is the ability to failover from my corporate office to the parent company and if need be from the parent company to the corporate office.
Ideally I would take the /24 I hope to get from ARIN and split it in half. Advertise half here at corp and the other half at the parent company datacenter.

Very new to BGP. Any advise would be greatly appreciated.
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Gary DewrellSenior Network AdministratorAsked:
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Hassan BesherCommented:
why you don't advertise /24 block and BGP peering will take care of failover, it will be slow but if there is bfd support it will be much faster.
Well for many reasons spiltting up a /24 is not a good idea.

The biggest reason is the smallest subnet an ISP will advertise is a /24, so you're not going to be able to to split a /24 up and advertise it from two different sites.
Get a /24 (if ARIN still has addresses left) and advertise it to both your ISP, and to you parent company - and ask them to advertise it to their two uplinks.

Add a few prepends towards your parent company, so not much traffic will come on that link. The parent company itself can set higher local preference in order to use the link for traffic from themselves.

Take only default route from both your ISP, and parent company - plus ask parent company to advertise you also their own networks. Set higher local preference on the default you receive from your ISP.

With this you do not need to take the full table, so any cheap router or L3 switch can do the job. You will have fail over, not load balancing.
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He can't get  a /24 from ARIN, the small they will hand out is a /21.  If all he can justify is a /24, then it will have to come from one of his ISP's.
Perhaps he can get a /24 from the parent company, and at then use also the same AS number.
Gary DewrellSenior Network AdministratorAuthor Commented:
According to the policy on Arin's website an end user can get a /24.  An ISP has to get at least a /21.

If I can get a /24 one of my providers, is it it pretty standard that the other providers would advertise it for me?
Yes, /24 and larger networks are exchanged between ISPs globally.

You also need an AS number.

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Gary DewrellSenior Network AdministratorAuthor Commented:
Thanks Pergr. I will contact our parent company and see what I can do.
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