North American Network Operators Group
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Re: Server Redundancy

  • From: Paul Vixie
  • Date: Wed Aug 06 19:02:11 2003 
Using outboard appliances for "server load balancing" is unnecessary,
and it adds more powered boxes (thus decreasing theoretical reliability).

If your upstream router can speak OSPF and is made by either Cisco or
Juniper then it will implement ECMP (equal cost multipath).  If you put
your "service address" on lo0 as an alias, and you run Zebra or GateD
on the "service hosts" which possess that alias address, then each such
host will appear to be a router toward the service address as a "stub host"
and your upstream routers will dtrt wrt flow hashing for udp or tcp traffic
(that is, the udp/tcp port number will figure into the hash function, so
you won't multipath your tcp sessions.)

This is how f-root has worked for years.  Look ma, no appliances.
-- 
Paul Vixie