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Setup failover/high availability network


I need some help to make a decision to implement Dual ISP failover network architecture.

My first question: In case my ISP crash, I will have a problem. So I want to add another ISP and router to my current production environment. I want to know what equipments I need and how to implement it as the case in "Resillient Blueprint" .


Der Fu


Re: Setup failover/high availability network

Huge topic with no one answer - depends on your goals, network in place currently and money. More likely than not you will end up with BGP if you dual home to 2+ ISPs. So to that end here is a link on BGP:

Also, look into getting the book Internet Routing Architectures by Halabi. It is a great source for BGP.

Generally you probably will have 2+ routers connecting to 2+ ISPs (at different C.Os in the rare - but does happen - chance a CO dies) running BGP with IP addresses you own (ie that are portable). BGP will load balance/redundancy on WAN side and run a routing protocol (eg OSPF or EIGRP) and/or MHSRP for the LAN side.

Hope it helps.



Re: Setup failover/high availability network

Halabi's book is a great book, but overkill for your situation... You could also take a look at my book, which focuses on the availability aspects and ignores load balancing and other topics. Chapter 8 goes through a wide range of redundant ISP strategies, includes sample configurations, and points out many aspects aside from BGP routing which you need to consider if you actually want to see improved availability for your money. For a quick overview, check out the Multi-homing white paper on my web site. It will give you a quick overview on the wide variety of solutions you can choose from, most of which can be done with the smallest router which will handle your traffic load.

By the way, focusing on ISP failure is ignoring the two most likely failure modes which will knock you down-- your local loop to the nearest CO (good luck getting a physically diverse second local loop!) and your own facility (power, hardware, configuration errors, clumsy workers, etc.). Unless your ISP is fly-by-night inc., both will contribute far more downtime than the ISP. You may find that diverse routing to two different POPs of the same ISP will buy you almost as much availability and greatly simplify load balancing and your configuration.

Good luck and have fun!

Vincent C Jones

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