3 ISP's?

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Jun 9th, 2008
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We are evaluating bandwidth options as we have 2 DS-3's to two different ISP's one option would be to add another DS-3 to a third ISP. What is best way to do load-balancing across the three while providing redundancy?

Do I need to look at OER / PFR for this? Or just let BGP do it's thing on it's own?

Thanks in advance

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spremkumar Mon, 06/09/2008 - 21:35
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Hi Phillips

Whats the current setup out there with 2 ISP's ?

are you running bgp between them or using simple static maintaning redunandncy alone ?

do you have your own public ip address space available with you at present or using the blocks provided by those ISP's ?

I strongly feel keeping the gateways of ISP's in mind you can take a decision so that your connectivity remains intact though one of the ISP's gateways goes down.

Also better possible solution would be to run BGP with them and take ethernet based solution with them so that u can upgrade the bandwidth at any time without much of any hardware upgrade.


paolo bevilacqua Tue, 06/10/2008 - 02:48
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For any environment that doesn't want to become a testing house, I would leave things plain and simple with BGP.

Joseph W. Doherty Tue, 06/10/2008 - 05:30
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Assuming your focus is on outbound load balancing, OER/PfR provides dynamic link load balancing. Although Paolo's post should be seriously considered, just outbound dynamic link load balancing is a minimal impact (to the routers) OER/PfR configuration. For over a year, I've been using OER on about 40 routers in a more complex configuration (one that also supports end-to-end analysis) and have found it appears to work.

PfR, I believe, can also support inbound dynamic load balancing. This, though, would be considerable more complex and problematic to make effective especially working with multiple ISPs.

ftikphillips Tue, 06/10/2008 - 07:14
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Currently we are using BGP for the two ISP's. My issue is that I have the two ISP's coming in to two different MUX's one of which I can easily add more bandwidth, so I can take one of these to an OC-3, but the other MUX can't take on additional bandwidth so in a failover I would be cut down to one saturated DS-3. Where if I could just add another DS-3 I add capacity and keep a decent level of redundancy. All options are on the table I was just curious about routing over the three ISP's.


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