Multihomed server for backup & load balancing

[Kevin Darcy]

Nate Duehr wrote:

> On Thu, Feb 15, 2001 at 04:56:30PM -0500, Kevin Darcy wrote:
>
> > I think you'll find that *most* clients will eventually fail over, but
> > the failover timeout will vary from client platform to client platform.
> > Of course, if a client is lucky enough to get the live address first in
> > the address list, then there's not timeout at all.
> >
> > One huge advantage of something like Local Director or BGP4 (I assume
> > that's what you meant; I've never heard of "MGP4") is that they eliminate
> > the timeout completely. Also, the higher-end products allow you present a
> > whole farm of servers as a single address and to dynamically shift the
> > traffic between them as load conditions change. They are therefore a much
> > more elegant solution than plain old DNS "round-robin", although often
> > very expensive...
>
> Kevin, this sounds like you have personal experience with the
> LocalDirector.  You have me curious now.  Does the Cisco LocalDirector
> properly load-balance DNS traffic against multiple real servers?  Seems
> like it would be rather interesting to get this to work.
>
> Now you have me wanting to go read through the documentation on my
> employer's load-balancer du jour, the Alteon to see if they do this or
> not.
>
> Other questions I would have would be are the real servers on
> non-routable IP addresses (10.x.x.x, etc.) or real IP's behind a NAT in
> the load-balancer.  Seems like the servers themselves would be quite
> confused by having private-side addresses and this would cause a number
> of problems with doing recursion from them -- the replies may not get
> back to them from other nameservers if the NAT isn't done right.
>
> Now you have me REALLY curious.  I'm going to have to grab a notebook
> and pen and draw up a few hypotheticals about how this might (not) work.

Sorry, but my knowledge of Local Director is only theoretical/second-hand. I'm
not sure whether it's really suitable for front-ending nameserver farms,
although I seem to recall that Alteon claimed to be able to do that.


- Kevin