Re: [Xen-users] Networking on Xen box

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

Stephen Liu wrote:

> Host - Debian Etch Workstation
> Guest01 - mail server for routing
> Guest02 - mail server, hostname01. localIP01, domain01
> Guest03 - mail server, hostname02, localIP02, domain02
> Guest04 - mail server, hostname03, localIP02, domain03
> etc.
>
> all mail servers running postfix as MTA on Debian Etch.
>
> single (one) external IP with all ports forwarded to Guest01 except
> port 53 which is forwarded to the DNS server, also running on a guest
> of the Xen box.
>
>
> Guest01 routes all incoming mails according to their domains to
> respective mail servers.  All outgoing mails are sent via the routing
> mail server, Guest01, to Internet.
>
>
> The system is working nicely on Intranet.  Mail client, Evolution, on
> workstations connected to local network, the Intranet, can send/receive
> mails on the mail servers.  Server settings on mail client work on
> either local IP or on hostname. 
>
> My question is if the workstation is on remote site, not on local
> network.  What will be the server settings on the mail client.  If on
> external IP how can the remote mail client find the mail server which
> it needs to connect.  Please shed me some light.  TIA
This has nothing whatsoever to do with Xen - it is a standard 
networking problem in working around a broken network. <rant>NAT == 
Broken, no if's, but's or maybe's, it's BROKEN. The sooner people 
realise that NAT isn't an answer, it's part of the problem, and we 
move to IPv6 the better</rant>
Quite simply, you need to port forward whatever ports you use for 
client access to the appropriate server. BUT, you have 3 (or 4) 
servers the clients could need to access. Therefore you will need to 
use different ports to access different servers. Eg, if you use IMAP, 
then you would be able to use the standard port on one server, but 
would have to use different ports for the others.
Alternatively, get your clients to use a VPN to access the local network.

--
Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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