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How avoid situation of IP address conflict?

Posted on 2004-04-26
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Last Modified: 2013-12-14
I have wireless network.User are connected using avaya wireless routers and APs.
First computer ( W2000 server) runs ISA server and act as internet gateway. It uses one public IP address and his local network IP address is 192.168.0.1 (255.255.255.0)
Second computer (W2000 adv server) is domain controler and DHCP server. IP address of this computer is 192.168.0.2
DHCP server gives users addresses from 192.168.0.100 throu 192.168.0.254.
Problems occur when some user enter manually IP address of one of my servers or ip address of some other user.
How disable user to make situation like this or how to disable user to see other computers in network neigborhood. It is enough user can authenticate on my domain controler, and get connection on internet using my ISA server.

Thanks!
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Question by:cutuk
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Expert Comment

by:mikeachilles
ID: 10987927
Hi cutuk.

You should be able to manage this problem by controlling the type of account users have on their computer.  A non administrator or power user should not be able to statically configure their IP address.  Are you also asking how to disable users from viewing the network neighborhood?
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Expert Comment

by:grblades
ID: 11005525
Could you please reword the following question as I can't follow exactly what you mean
"How disable user to make situation like this or how to disable user to see other computers in network neigborhood. It is enough user can authenticate on my domain controler, and get connection on internet using my ISA server."

So the windows DHCP server will issue an IP lease even if that IP address has been statically configured on a machine by mistake.
This is probably not what you want to hear but I would use the standard 'dhcpd' in Linux as it will attempt to ping the IP address to make sure it is not in use before issuing the lease.

As you have an ISA server you should be using WEB encryption on the wireless lings to stop anyone from being able to sit outside your office and browse the internet using your bandwidth.
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Author Comment

by:cutuk
ID: 11007926
Hi mikeachilles, grblades
Sorry I was unable to answer yesterday.
Also, sorry I was not enough specific.
I have two computers at my office, and broadband interent connection. One of computers runs MS ISA server ie. internet proxy server, and gives me ability to share internet connection with other users. Second computer is domain controler. It is also a DHCP server. Beside this, I have a wireless infrastructure wich consists of four wireless access points connected using AVAYA COR,ROR bridges/routers. My clients are independent of my network, they have their own administrators and their computers runs W95, W98, XP etc.
In other words, you can see, it is a small internet service provider, who gives service for 50 clients.

When client enters as network card IP address, IP addres of the MS ISA server I noticed two things can happen:
1. MS ISA server notifie me that IP address conflict occured, and the client  losts connection.
2. Second situations is when the MS ISA server become unreachable, and no one of my clients have internet conection.

I want to know what I have to do to make my computers safe from situation described in second case.
I hope you can see now what I wanted to ask. Please sorry for my english.
Thanks!
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Accepted Solution

by:
grblades earned 500 total points
ID: 11008378
The problem sounds like some machines are being configured with the same IP address as your ISA server. I assume your ISA server connects to the internet on one interface and there is another interface which connects to your local network?

What I would do is connect a router between the ISA server and the wireless access points. You can get the router to be the DHCP server aswell. That way all clients have an IP address on a different network and if they do configure one with the same IP as the ISA server the packets wont get past the router.

What speed internet connection do you have?
What else is the domain controler used for currently other than DHCP?
Is it used by any of the clients over wireless?
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