Load Balancing under Linux

[Bob Stocker]

On Thu, 2002-04-25 at 12:12, Gerald Combs wrote:
> On Thu, 25 Apr 2002, Jonathan Hutchins wrote:
> 
> > I asked a very high level ISP tech about this, and he said they use a
> > protocol similar to RIP and OSPF.  They handle a lot more traffic, and use a
> > Cisco router to do the balancing.  He suggested registering for RIP and
> > going with that.
> 
> A "very high level ISP tech" suggested you use RIP?  I'd find another tech
> if I were you.  What does "registering for RIP" mean, BTW?
> 
> While many dynamic routing protocols offer decent failover (BGP, OSPF,
> EIGRP, not RIP or RIPv2), most don't do load balancing very well.  None do
> decent load balancing on asymmetric links, e.g. two T1s and a fractional
> T3.  
> 
> We're using two Cisco 7200 VXRs as border routers here at work.  We have
> three T1s, two from one provider and one from another.  We're peering BGP
> with our upstreams so that we can fail over if any of the links go down.
> However, in order to perform proper inbound or outbound load balancing, we
> have to resort to things like route maps that shoot the traffic out a
> particular interface based on a regular expression applied to the
> destination ASN.  
> 
> BGP is a really fancy and cool protocol.  It's used to route most of the
> backbone Internet traffic.  If you want do dynamic routing with different
> ISPs, it's your only choice - most providers won't peer OSPF or EIGRP with
> you (I guarantee they'll laugh out loud at the suggestion of peering RIP).
> But it often sucks at load balancing.
> 
> Better solutions are coming down the line, like MPLS (Multiprotocol Label
> Switching), but they aren't here yet for most people.
> 
It could be that the ISP tech suggested RIP on the (very very) off
chance that both DSL providers are broadcasting RIP from their core or
gateway router(s) - a pretty wild supposition, but not beyond the realm
of possibility.  Anyway, RIP won't help with load balancing, and
probably won't help by giving you shorter route paths either.  
An even wilder supposition is that any DSL provider would ever consider
peering BGP with their DSL customers.  If you have the impossible good
luck of having two such providers, check out GNU Zebra (a gated
replacement) at http://www.zebra.org/ .

Good luck,
-Bob

PS:  I hope nobody minds that I cut out all the cc's.