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Date:      Mon, 10 Dec 2001 09:57:08 -0600
From:      "Dustin Puryear" <dpuryear@usa.net>
To:        "Gabriel Ambuehl" <gabriel_ambuehl@buz.ch>, <freebsd-isp@freebsd.org>
Subject:   RE: Re[6]: Using DNAT and DNS round-robin
Message-ID:  <PGECILGGNJGDPJKLFEMICELPCIAA.dpuryear@usa.net>
In-Reply-To: <48508292666.20011210105413@buz.ch>

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> Hello Dustin,
>
> Monday, December 10, 2001, 6:41:56 AM, you wrote:
> > Gabriel, after rereading your message I am now definately curious
> > how you go about this when using multiple webservers for both IP-
> > and name-based virtual hosting.
>
> Normal hosting consumers we simply setup as name based, those who pay
> for SSL we of course give their own IP but since none of these needs
> load balancing (and load balancing IS a major PITA since you need
> bullet proof filesystem synchronization for it which I currently
> can't
> see how it should be achieved on FreeBSD), we put all on only one
> server. To protect us against server problems, we mirror the servers
> every few hours to a twin in order to have a fall back option.

Our situation is a bit different as my client is not a web hosting provider.
Rather, they have their own web services that they will be offering to
existing customers. Since this is a high-load application, we want to be
able to spread the load across n servers. Also, to ensure best performance I
don't want to assign site A to server 1, site B to server 2, site C to
server 1, and so on. Rather, I would like to load-share (load-balance later
on) across all servers for any client.

I guess that is where the initial confusion came from. In order for each
webserver to offer the same IP-based virtual hosts as the other n-1
webservers, it appears that I need to setup the same IP alias on each
webserver, unless I am missing something. Obviously, that won't work. That
is one reason why I was looking at Squid.

I may be able to pressure the client into using only named-based virtual
hosting, which would clear this up. However, this is something I would like
to know how to solve, and I have a bad feeling it would only be a temporary
fix anyway.

I am surprised this problem isn't more common. I mean, someone out there
must be trying to spread several IP-based virtual hosts across n servers.

> > Okay, so I setup my firewall to route any packets destined
> > for network xyz to my internal web servers. These web servers may
> > be using IP- or name-based virtual hosting. Now how do I configure
> > the interfaces on the internal web servers?
>
> Simply give it the IPs you want them to respond to.

But then I hit the problem with n webservers all configured to respond to
the same IPs.

> > Since each web server needs to be able to serve any of the
> > websites, how do I handle each web server needing to have an IP
> > alias for one of our IP-based
>
> How do you go about providing all the data to all servers? I'd very
> much like to have a real time filesystem replication facility since
> then I could go for a setup like you want... It's easy with data that
> you control, since then you can store all volatile data in SQL db,
> but
> with hosting consumers, that's obviously not possible.

Well, we are one of those "we control all data" types. :)

> > virtual host? I think that is what is confusing me. If it was just
> > named-based virtual hosting there wouldn't be an issue in my mind.
>
> You simply can't have the same IP based virtual host on two machines.
> The online thing that can be done there is round robin NAT but for
> reasons pointed out above, that's major PITA.

That is becoming rather obvious to me at this point.

Regards, Dustin

---
Dustin Puryear <dpuryear@usa.net>
Information Systems Consultant
http://members.telocity.com/~dpuryear
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