DNS problem on internal network when no internet

[AlexandreAmant]

Hi,

I have an internal network here running a RH9 server and a dozen of WINXP clients. The network has an internet connection.
When the internet connection is down, the emails won't be sent & received from outlook on the clients as if the internet was needed for some kind of DNS resolution to access my internal server.
However, I have put the IP address of the server in the outlook settings and I have the server in the host file of the client.

Any idea ?

Thanks !

 

[gdvissch]

What kind of mail server are you using?
What is the DNS config of your clients and server?
Are you using Outlook or Outlook Express?
Do you have your own maildomain?
Are your clients sending the mail to the RH server or the mailserver of your ISP?

G.

 

[AlexandreAmant]

- Mailserver: QMail
- DNS config: using the ISP DNS. I've tried to set-up a local caching DNS, but it did not help.
- Outlook (not express)
- No we don't, but QMail relayes internally our own mail.
- Clients are sending the mails to the RH server (to QMail).

Even receiving from our RH server is a problem when the connection is down.

Thanks !

 

[bcastner]

Either configure a local DNS server, or purchase a router.

 

[AlexandreAmant]

I had a local DNS (caching) but it did not help.

And since I have my server in the hosts file of the clients, I don't actually see why I would need a DNS.

And why a router ?

bcastner: I don't understand the logics behind that, can you explain ?

Thanks,

@lex

 

[bcastner]

My concern is that you lose your gateway when the network connection is down.

(I also cringe at having your machines exposed this directly to the internet. NAT is a good thing).

If you were using a private IP range, with a local gateway address on that subnet, then the internet going down would not affect your local LAN traffic.

 

[AlexandreAmant]

Hi,

My gateway defined on the clients is an internal machine that does NAT (XP with 2 NW cards - basic but works). One is connected to our network and the other one to the ISP.

I am thus using the 192.168.x.x range for my internal network.

So I don't think it is the problem...

 

[bcastner]

So you are using ICS to provide routing for internet access to NAT'ed clients behind the ICS Host.

There are some subtle things about assigning static IPs in an ICF setting:

http://support.microsoft.com/default.aspx?scid=kb;en-us;Q309642

. Note the default DNS, and default Gateway entries for the clients;

. Note the naming convention for workstations

. Note the special requirements of the ICS Host HOSTS file.

 

[AlexandreAmant]

Thanks for that info, very useful (I indeed use ICS).

But it still does not work. I've applied all the settings, changed the hosts file as per what MS is saying and when I unplug my internet connection, I still cannot send or receive emails.

And I have the IP addresses in outlook and not the host name, so I really don't understand...

Thanks !