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When server gets disconnected, client computers lose internet.
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Morketh
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Default When server gets disconnected, client computers lose internet. - 08-24-2011, 03:21 | posts: 2,903 | Location: Houston, TX

Alright I do not understand what is going on here.

I am onboard a vessel that has internet on it. The domain server is also the DHCP and DNS server for this network.

When I go to the client PC and open the network connection settings they are configured automatically. So I change them to set the ip address / subnet / default gateway / and dns server and the internet works. If I take the DNS server out, internet will not work.

Also if I disconnect the server, internet stops working on all client computers.

Why do you think this is?
I even plugged one of the client computers into the same port on the switch that the server was plugged into just in case that port was configured in some way and still nothing.


I need to take this server down to rebuild it and I cant have them with no internet while I'm doing it...

Any ideas?
Why do these computers require this server to get internet?
   
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Extraordinary
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Default 08-24-2011, 03:24 | posts: 5,791 | Location: 127.0.0.1

DHCP turned off on the router ?

DNS settings incorrect on the router too ?
   
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Morketh
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Default 08-24-2011, 03:37 | posts: 2,903 | Location: Houston, TX

Its a possibility man, I did not set their router up and honestly I do not know how to configure cisco routers. I will have to call the company who set all this up and see if they know anything about it, they just don't open til another like 5 hours though and I need to get this figured out!
   
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Default 08-24-2011, 03:49 | posts: 9,775 | Location: UK

I would expect this behaviour if the DNS server is also used as the Gateway, is that true?

If not, when there is no DNS server, can you access sites directly using the sites IP?
   
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grunger
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Default 08-24-2011, 06:18 | posts: 1,861 | Location: London

The DC is giving out IPs, and will be pointing clients to itself as the DNS server.

DNS is disabled on Ciscos unless specifically enabled and as this is a domain network it is probably (quite correctly) disabled on the router.

So with the server powered down I suspect you can ping an external IP, but not a FQDN. If you manually set and IP with an external DNS server (8.8.8.8 for example) it will probably work.

However if you do that you will very likley experience internal problems with logins etc as it will be looking for the DC and won't be able to resolve it via external DNS.
   
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deltatux
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Default 08-24-2011, 06:38 | posts: 19,054 | Location: Toronto, Canada

If the DNS server handles DHCP, it may as well be a router at the same time. Often smaller companies would use their central server as a router like my dad's office. I never knew it was the router until I took his server offline for a small maintenance, thought it didn't disrupt the office traffic but boy was I wrong, I quickly checked what I needed to check and then powered the system back on.

The iptables on the server was the mechanism that routed traffic.

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Default 08-24-2011, 08:39 | posts: 1,242 | Location: Melbourne, FL

It's because your client computers are connecting through a domain. Basically a domain is a type of security feature across your network to authenticate types of services. If your network is designed around using a domain then yes if the domain server goes down many things will not work including potentially internet access.

Mind if I ask what OS the server is running and what is wrong? Can it be repaired without reloading the OS?

I only ask because with only a casual knowledge of this then it can be complex to reconfigure your domain. If you don't have the required information, you definitely may need to speak to the original tech who configured the system...

Last edited by Brendruis; 08-24-2011 at 08:45.
   
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TruMutton_200Hz
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Default 08-24-2011, 09:57 | posts: 2,767 | Location: Belgium

It's possible to build a socalled smart switch based on a cheap computer, running on Linux, that can be used as a dedicated machine to offer all of the functionalities of a Layer 4 switch - a router / firewall combined with a QoS (load balancing) server. This can be used as a temporary (or perhaps even permanent) replacement of a server that's being used as a proxy / DNS. I've read it's a commonly used solution because it's so cheap. Don't ask me how to set it up correctly, though.
   
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