[Charlug] Web-server Farm - Networking Question

[Jason Edgecombe]

David Simmons wrote:
> I know what I'm hoping to do....I need help in understanding which
> technology/buzz-word to research and RTFineM on.
>
> Situation:
>
> Physical CentOS server with a single, static IP address....with
> multiple virtual machines - each VM (also linux / CentOS based) set up
> for web-hosting (LAMP with ssh/ftp access).  Say VM1 hosts
> www.somesite.com.....say VM2 hosts www.anothersite.com.....and say VM3
> hosts www.finalsite.com
>
> I'd like to setup DNS to point to the single 'real-world' address -
> but have the individual VM respond to the request.
>
> What technology do I use so that all of the virtual machines are seen
> on the 'real' static IP address to the world?.....so that people on
> the internet can SSH into their own box (which is just a VM on the host).
>
> I've been researching Multi-homing.....and Linux Virtual
> Server.....but some of the howto's/docs are ancient.
>
> Any book / site / howto suggestions?
>
> Thanks in advance - Dave
Do you really need multiple IPs? or do you just need to host multiple
domains on one server?

If using Xen/Vmware with a IP for each guest, then pick an IP for each
host/guest and use the bridging virtual network adapters and setup
static IP's like a physical host.

If you really only have one IP, then you should consider setting up a
normal shared-hosting arrangment. Normal shared hosting uses one IP and
hostname with multiple DNS aliases to the real host. This works well so
long as no one needs root access and https isn't involved. The SSL certs
for https complicates matters and requires either a special wildcard
cert or multiple IP's for the same box.

If you really want multiple guests on one host with one IP, then you'll
need to setup apache on the host with something like mod_proxy to
forward to the guests. you would need to set up ssh on different ports
and forward from the host to the guests.

BTW, dns aliases work fine for ssh access in the shared host scenario,
you just use the username to differentiate the access.

There are several OSS control panels available for shared-hosting. For
Xen, there is Enomalism for Xen management. for VMware, pay megabucks
for VirtualCenter.

Do you only have one internet accessible IP address? Are VM's required?
Do the users require root access or super special setups?

Sincerely,
Jason